good afternoon and welcome back today we're going to be covering chapter 3 the cell and might be self-explanatory we're going to talk about the structures in cells and compare them between eukaryotic and prokaryotic cells which will be the bulk of what we talk about in the chapter but before we really get into that we're going to take a quick look at the history behind cell and some modern cell theories similar to what we did in the first two chapters we're going to talk about some of the early scientists that provide the information about cells and cell structures and how that leads into some more modern cell theories such as cell theory and the endosymbiotic theory and then we'll move into a comparison between the eukaryotic and prokaryotic cells so what we're seeing here is just a variety of microorganisms they all have cells now they may they may differ in structure and appearance a bit but as living organisms they have their cells that are present in all of these organisms so you've got a proto so on the Left it looks like some sillas here in the middle it's more protozoa some spirochetes and here you've got some red blood cells and again another protozoa and this looks like a large single eukaryotic cell all right so we're gonna start with spontaneous generation which was an early IC theory but I use that term loosely that life just a it spontaneously appeared from inanimate objects we know that that's not true now we'll talk about some of the early theories and how we moved away from that with science first the clinical case study we'll be talking about in this chapter you have Barbara a 19 year old college student she's in the dormitory in January she came down with a sore throat headache mild fever chills in a violent but unproductive cough meaning that no mucus is produced so we've heard that recently with the SARS Cove - virus one of the symptoms of Kovan 18 the disease that it causes is an unproductive cough so to treat those symptoms Barbara began taking an over-the-counter cold medication which didn't seem to help in fact over the next few days while some of her symptoms began to recede or resolve her cough and fever persisted and she felt very tired and weak so what types of respiratory disease may be responsible well this is pretty broad right so it could be anywhere from a upper lower respiratory tract infection to pneumonia or influenza usually the mild fever would indicate it's probably not influenza but this is this could be a quite a few different types of respiratory infection all right so back to spontaneous generation so it's an early theory and again you note that I included quotation marks here and I'm this well this isn't the outline I want to cover the difference between a hypothesis and theory this is an early theory that life arises from nonliving matter so the reason I provide this is a lot of times in common usage we use the word theory incorrectly right you might say oh I have a theory about that really what you have is a hypothesis so a hypothesis is a suggested explanation for an observable phenomena so it should be testable and falsifiable so that right there testable and falsifiable are two very important terms relevant to observational science or even the designing of experiments you have to be able to disprove something and that that's something that often gets lost in what we consider to be a theory or not so a theory though is well it's a tested well substantiated unifying explanation for set of verified proven factors so somewhere over you might hear this right is when somebody's talking about the theory of evolution and they say well it's just a theory and again we're misusing that term when they say it's just a theory there's they may be saying more accurately well it's just a hypothesis the the theory of evolution the the law of gravity these are things that are very well-established there is an overwhelming amount of evidence to support them so to say it's just a theory is is not using the term properly so just wanted to point that out because to me this it's more a hypothesis of spontaneous generation because there really wasn't any evidence to support it they looked at fish appearing in a mud puddle where there hadn't been fish before and they said oh they must just appear in there automatically so a pretty poor hypothesis of that so Aristotle though was one of the earliest recorded scholars that proposed spontaneous generation you believed that life would arise if the material contained Numa or vital heart and as evidence he pointed out fish in a puddle of water sudden appearance of animals environments where none had been one of the ones that all that we'll will touch upon is the appearance of maggots on meat and they thought that the fly the larvae the maggots were just appearing spontaneously generating on the meat and we know that that's not true now so it starts a little bit here so some of the the contributions to this early poor hypothesis were john baptiste oh van Helmont so in the 17th century he proposed that mice could arise from rags and wheat kernels if it's left in an open container for three weeks it turns out that that's just it's great food for mice and they like to make their nests in that right so they find that and anybody's had mice you know that they can get into very small spaces they can they can they're pretty hard to keep out if a food source like that francisco redi refutes that i the idea that maggots spontaneously arise for meat they predicted that it flies were prevented from landing on the meat maggots would not appear so he develops an experiment where he takes six containers all filled with me he has two that are open to the air two that are covered with gauze that prevents the fly from landing on the meat and two that were tightly sealed with a cork like a cork cap I guess or plug that prevents fly so I'm getting into there and as predicted maggots only appeared in the open flats they appeared in the open one on the meat they appeared on the gauze in the gauze covered and not at all in the tightly sealed John Needham still along this theory of spontaneous generation he takes broth and it fuses it with plant or animal matter and briefly boils it and that briefly is the key word so at this point he's intending to kill all the microbes that might be in there and seals the flasks so when they become cloudy at a different / different time and I included the word turbid here that's something we'll use throughout the semester so when you have a tube that when you start with broth it'll be clear and then it becomes turbid or cloudy that's an indication of microbial growth so that the flaw in his study was that he didn't boil those flasks for long enough he didn't kill all the microbes in the broth so they were able to grow even though they were sealed so lazzaro spallanzani comes by he repeats this experiment but he increases the heating time and no growth occurred until the flasks were later open to the air so he suggested that the microbes were being introduced from the air Needham not giving up yet countered that there is a life force that was destroyed during the extensive boiling so here we have Francisco Reddy's experiment and as you can see again the open container the Flies land lay the maggots the maggots grow but when it's covered or the gauze the maggots do not appear on the meat this is an example of a good experiment I have a control group and it's like I said it's provable or falsifiable which is important so here we just have some pictures of ready on the left it's quite an hairdo we have John Needham in lazzaro spallanzani alright and Louie Pasteur comes along it's the name we're going to we're gonna encounter a lot in microbiology so he created an experiment using these swan-neck flask s' and he boils a broth in the flasks to sterilize that excuse me and the curve in the swan neck air can enter but any spores or bacteria that are airborne are going to get stuck in this u-shape on the flask so they're not going to be able to enter into the the broth also Louie passed or he filtered air through guncotton and then examined it under the microscope and he could see that there were probably spores and bacteria that were filtered out of the air so when he designs designs this experiment what we see is that the broth remind remains clear not turbid until they removed the swan neck flask and now it allows air to enter into the flask and then it becomes turbid there's back there's microbial growth alright so foundations of modern cell theory so modern cell theory there's a little bit more to it but the two important things here are all cells come from pre-existing cells and cells are the fundamental units of organisms so you might recall from chapter one I talked about a cellular pathogens like viruses and prions and Vera soit's and Vera and I said that they weren't living organisms mother acellular they don't have cells therefore we can't be living organisms and then the other one all cells come from pre-existing cells and we can get into a little bit of a chicken or the egg here we're not talking about the very first living organism what we're talking about is new life meaning what happens an egg is fertilized until you talk about humans for this an egg is fertilized right the egg and sperm come together and they create a zygote that is the first cell that cell then divides to differentiate into every cell in the body so all those cells come from a pre-existing cell that zygote comes from pre-existing cells a sperm and an egg so these are the two main tenants of the modern cell theory so how did we get to this point though well it starts we already touched on this about Robert cook when we were discussing microscopes it was the first that observed cells in 1665 looking at cork so quite a bit later almost 200 years later Matt matthias schleiden it's a German botanist and he is looking at plant tissues under the microscope and he describes them as being composed of cells at this point he believed they were formed via crystallization not cell division but it's an important point this is when he starts to recognize that all these cells have are all these plants have cells a little bit later I think it's about 13 years later Theodor Schwann another German physiologist makes the same observations about animal tissue and then they talk and schwann starts to realize that when we have cells and plants we have cells and animals this is important this is where we start to realize that all living organisms are made of cells so you're seeing here the quark cells onion root tip cells you probably looked at in some sort of class at one point and if you had anatomy and physiology you'll recognize these cuboidal epithelial cells that are the tubules of kidneys here also we have rudolf virchow and robert remac [Music] so Robert remac was a neurologist an embryologist he published evidence that showed that cells are derived from other cells as a result of cell division this is when it again very important in leading to the the cell theory that we just touched upon Rudolf Virchow was considered to be the father of pathology and he popularized the concept of cell theory using the Latin phrase on the cellular cellular or all cells arise from cells which is essentially the second part of the modern cell fear that we talked about all cells are coming from pre-existing cells all right so that leads us to the endosymbiotic theory and this is this is an interesting one I'll cover this in just a moment but basically there's a lot of evidence to support this is that the chloroplasts and mitochondria were early bacteria that were engulfed by a early eukaryotic cell so the eukaryotic cell absorbs a bacteria and that bacteria in the eukaryotic cell then have a symbiotic relationship which eventually evolved to the point where the chloroplast implants the mitochondria and animals two separate events occur but they're absorbed in the same way and they lose genes because they no longer need them it doesn't become important for them to be able to do anything other than produce energy and replicate so a lot of the genes were lost that came very simplified and eventually they become chloroplasts and mitochondria so how did we get there well it starts with Robert Brown so the Scottish botanist in 1831 he notes that plant cells have a nuclei andryush Schipper as a german botanists and early 1800s he observes and describes chloroplasts of plant cells and noted their role in starch formation during photosynthesis and noted that they divided independently of the nucleus they're not replicating the through cell division the same with the nucleus is they replicate in a different way remember for photosynthesis were taking UV light and converting it to a carbohydrate in this case starts oh he's just observing this photosynthesis and notes that they that they divide independently konstantin Mayer sakowski Russian botanist in 1905 he proposes that the chloroplasts had originated from ancestral photosynthetic bacteria that were living symbiotically inside of a eukaryotic cell in a moment we'll look at a diagram of this but I want to get through just sort of the ideas hopefully this makes sense it makes a similar hypothesis for the nuclei of plant cells that these you early eukaryotic plant cells absorbed a photosynthetic bacteria and it became a chloroplast sorry I think something's wrong here I'll correct it but also that the same thing occurs in animal cells they absorb a pro a prokaryotic cell and that develops and becomes the mitochondria I think this is saying the plant cell twice I'll correct that either Wallen is an American anatomist he he notes that they're similar similarities between mitochondria chloroplasts and bacteria so this is the beginning of where we really start to gain traction on this and it isn't until in the 1960s where we were able to start looking at the gene sequences of mitochondria and chloroplast DNA where we really start to see that they are actually much more similar to prokaryotes than eukaryotes so eukaryotic cells have photo they have chloroplasts and mitochondria in them that are much more similar to bacteria than they are to the cells that they're in and that really supports this idea they note that microscopically genetically from the molecular biology fossil and geological data all seem to support this that that these events had occurred all right so again the endosymbiotic theory is mitochondria and chloroplasts arose as a result of a prokaryotic as a result of prokaryotic cells establishing a symbiotic relationship within a eukaryotic host so what kind of genetic evidence supports this well there's gene sequencing and phylogenetic analysis that show that the mitochondrial DNA in the chloroplast DNA are very closely related to bacteria not eukaryotic cells bacteria and both in the sequence of their DNA and in the structure of the chromosomes they're much more close with chromosomes much more closely resemble the circular chromosomes of bacteria the mitochondrial DNA and the chloroplast DNA are reduced compared to nuclear DNA I mentioned that right they lose those genes that are unnecessary they no longer they couldn't exist on their own but inside of a host cell they don't no longer need those genes the ribosome so if you remember ribosomes are organelles that synthesize proteins it turns out that the differences between eukaryotic ribosomes and prokaryotic ribosomes there are different size the mitochondria and chloroplast ribosomes much closer to bacterial ribosomes than eukaryotic ribosomes and finally all eukaryotic cells undergo mitosis mitochondria and chloroplasts don't they undergo binary fission that's very similar to the binary fission of bacteria so all these genetic all these genetic data seems to support the end of symbiotic theory as well all right so a little bit of a visual representation of what we just discussed currency of this proto which just means an early eukaryote it has in foldings of the plasma membrane that leads to the nucleus and the endoplasmic reticulum so remember one of the big things about eukaryotic cells is they have a membrane bound nucleus they have membrane bound organelles like the endoplasmic reticulum the Golgi apparatus etc so there's a first endosymbiotic event where this ancestral Uecker absorbs or consumes in aerobic bacteria it enters the cell here involves into mitochondria then a second endosymbiotic event occurs where an early eukaryote consumes photosynthetic bacteria that then involved into chloroplasts so we get our modern photosynthetic your eukaryote and we get our modern heterotrophic eukaryote all right so the next modern theory that was built upon these early findings was the germ theory of disease which is simply that certain diseases are caused by the invasion of the body by pathogens or disease-causing microorganisms remember we have this Greek miasma theory that these particles were released from decomposing matter and sewages or cesspits and they would cause illness so even as early on 15 1600s we were still wrestling with this idea that the miasma theory hadn't proved yet that they were caused by these microorganisms but in 1546 there's GMO fracas Thoreau an Italian physician he proposed that seed like spores could be transferred between people during direct contact exposure to contaminated clothing or through the air right much much more than just I would they float in the air and they make people sick so this is one of the first in the these first proponents of the germ theory of disease then you have Ignaz Semmelweis who's a Hungarian obstetrician and he notes that in these hospital wards and these maternity wards that the doctors and medical would go right from doing autopsies on corpse to do an Imagine expect inspection so he noticed that women that gave birth in hospital wards with physicians and medical students who were doing this had a 20% mortality rate and they were contracting puerperal fever after childbirth so 10 to 20 percent of these mothers were dying as opposed to midwives who weren't doing these autopsies where the infection rate was only 1% so he proposes hand-washing with this chlorinated hand wash for doctors and medical students when they started doing this the infection rate drops to 1% by the way puerperal fever is a bacterial infection of the upper genital tract it's most commonly caused by beta him a lot hemolytic streptococcus or Lancefield Group a and we haven't gotten into this just yet streptococcus we've touched on a little bit right there round-shaped streptococcus means that indicates that they're in a chain beta hemolytic means that they're able to break open red blood cells to extract oxygen but these typically when these bacteria beta hemolytic they are more pathogenic so this would typically be the same organism that causes strep throat all right so continuing on with this evolution from the miasma theory to this modern germ theory of disease you have John Snow all kinds of jokes free here he's a British physician in 1848 I only study the source of Colorado brakes in London so he was actually able to track down the source of these outbreaks to to water sources both of which were contaminated with sewage and we know now that that is how cholera is transmitted when fecal matter enters the water supply can cause cholera so this is the first known epidemiological study and in the first time that we responded with a public health response to an epidemic so also added this these two definitions because may not be aware of the difference between an epidemic and a pandemic right so let's say for the state of Georgia there are ten cases a year on average of measles but in this year we spiked 200 cases of measles that would be an epidemic right any time you have an increase of a particular disease in an area beyond the normal level that's an epidemic pandemic is when it affects multiple countries or continents I'm sure everybody can think of an obvious example of that right now alright so as a note the work of Semmelweis and Snowe showed that diseases could not only be transmitted through the air but they could be transmitted via contaminated surfaces as well as through the air in this case drinking water and through the hands of the physicians right so this refutes those miasma theories and starts substantiating this germ theory of disease once again Louis Pasteur in 1856 he discovers that fermentation is caused by microorganisms this swan-neck experiment shows that airborne microbes not spontaneous generation were likely responsible for food spoilage fermentation and affection and again provides more of a foundation for this germ theory of disease Joseph Lister is a British surgeon so at this point 50% of surgical patients were dying of infection after after surgery so he's trying to determine the cause of these post surgical infections so he proposed hand-washing and using cleanliness during surgery later began using phenol spray for carbolic acid as a disinfectant antiseptic during surgery which leads to a large decrease in infection rates I didn't put it in here but my lieutenant maybe use these words interchangeably disinfectant an antiseptic antiseptic is a chemical that's going to decrease the microbial load in is used on living tissue disinfectant is used on inanimate objects right so Lysol you wouldn't use it on your skin you would use it on a countertop right but we cure a chrome which we don't really use anymore but or rubbing alcohol you can use that on your skin that's an anti septic alright last we have Robert Koch touched on a little bit chapter one I need propose the Koch postulate so it's a series of these postulates that demonstrate a particular microbe could be attributed to a specific disease one microbe one disease so he and his colleagues were able to make the connection for cholera anthrax and tuberculosis so I think it's chapter 15 will look at these Kotla scope postulates and we'll see really what it is if you've ever done postulates and math it's a series of observations that you have to make right so you have to somebody's sick you have to be able to extract that virus or bacteria from them and that bacteria that virus can't be found in a healthy person and if you were to take a healthy person and infect them with that bacteria virus it would cause that disease so we'll get into that any more depth I want you to understand really what it is and it's just showing that you know the measles virus is gonna be is gonna cause the measles Mycobacterium tuberculosis causes tuberculosis so all right so we've got mr. Semmelweis here Joseph Lister and Robert Koch all right so we're back to the clinical case here so after suffering fever congestion cough increasing aches and pains for several days Barbara suspects she has a case of the flu which would be caused by the influenza virus she decides to visit to the health center and or university there's a physician assistant there tells Barbara her symptoms could be due to a range of diseases such as influenza bronchitis pneumonia or tuberculosis right so influenza is gonna be caused by the influenza virus or in Qaida's as infection of the bronchioles of the lungs pneumonia can be bacterial or viral and that just means that the the sacks and the lungs are infected and then tuberculosis which we just discussed is caused by Mycobacterium tuberculosis so during the physical examination the PA notes that Barbara's high heart rates elevated using a pulse oximeter so clips on your finger passes light through the finger and measures how much oxygen there is in your blood he finds that Barbara has a hypoxemia which is lower than normal level of oxygen in the blood using a stethoscope the PA listens for abnormal sounds made by Barbara's heart lungs and digestive system as Barbara breathes the PA hears a crackling sound and notes a slight shortness of breath so it collects a sputum sample notice it has a greenish color it orders a chest x-ray which shows a shadow in the left lung all these signs are suggestive of pneumonia a condition which the lungs fill with mucus so again pneumonia can be bacterial it can be viral it can even be fungal all it means is that there's an infection all the way down has to get down through the into the through the upper respiratory tract into the lower respiratory tract through the primary secondary tertiary bronchioles all the way to the sacs where it's then going to cause an infection there alright so we'll come back to this and we'll have a little bit more information on so you have a historical timeline here really this is what we just covered so I won't run through it again but another way of looking at the experiments we just covered all right so section 3.3 the unique characteristics of prokaryotic cells so we know that all living organisms are composed of cells and there's a few things that all cells have whether that's a prokaryotic cell or eukaryotic cell and that's what we're covering here so cytoplasm and cytosol it's a gel-like substance of water and dissolved substances important for growth it's contained within the plasma membrane so inside the cell you have this watery gel like mixture and everything's dissolved in that and that's it's important because most reactions occur in an aqueous environment if this were dry inside there it would be very difficult to have these components all come together for the purposes of life so every known cell has cytoplasm or cytosol in it all these cells have a plasma membrane which is also called a cell membrane or a societal plasmic membrane and this is a phospholipid bilayer in most cases in a very few cases it's a mono layer but typically a phospholipid bilayer and we'll look at a dock a diagram of that a little bit later and inside of this membrane you find the contents of the cell the cytoplasm your cytosol all cells have chromosomes we know you have to have genetic information so there's one or more chromosomes they contain all the genetic imprints of the cell it's gonna be composed of DNA for all living organisms the only exceptions are going to be viruses or prions or or prion proteins but the vera soit's and barrels can be RNA as well but for everything else everything that we consider to be a living organism this genetic information in the chromosomes would be DNA lastly everything's made of proteins so it should make sense that you have to be able to make proteins which means you have to have ribosomes so this is organelles where protein synthesis occurs the sizes are different between eukaryotic cells and prokaryotic cells and we'll get to that in a little more detail what are the differences between prokaryotic cells and eukaryotic cells so hopefully I've established this already right prokaryotic cells do not have a membrane bound nucleus versus eukaryotic cells they do they have a nucleus in prokaryotic cells we have what's called a nucleoid which is a loose area where we find some of the same things but you don't have that memory prokaryotic cells generally have a single circular chromosome located in that nucleoid versus eukaryotic cell typically have multiple rod-shaped chromosomes contained in the nucleus prokaryotic cells generally lack membrane bound organelles we've already established eukaryotic cells do have them right nucleus the endoplasmic reticulum all those organelles prokaryotic cells have inclusion bodies and there are little parts of the cytosol that compartmentalize and they're used for storage and it's also helpful to reduce osmotic pressure something we'll get to in a bit eukaryotic cells typically are larger than prokaryotic cells so you have to compartmentalize to keep those chemical reactions happy and happening in a particular area and we to do that we use complex membrane bound organelles this is important to understand the the typical structural differences between prokaryotic and eukaryotic cells alright so some common prokaryotic cell ships we touched on this in Chapter one or two you have the caucus or cox i which are round shaped bacillus of bacilli rod-shaped Vibrio which is a curved rod kako bacillus which is a short rod that's a little bit more round than than the rod and then you have spur alum or spur Lea which are spiral shaped and spirochete which is a long loose helical spiral so these are the the six shapes that you would typically see and mostly what we would see in lab would be these two iron and bacillus you also have arrangement of those cell shapes so you can have single you could have a duplicate so caucus is one caucus diplococcus is two cox i and then range together you have tetrad which is four cox i arranged in a square you could have streptococcus which is a chain of cox i Staphylococcus which is a cluster of cox i and bacillus which is a rod instructor sillas which is a chain of rods so how is that sell a house that morphology maintain well typically it's through the cell wall and certain cytoskeletal components so there's a cell wall as found in most prokaryotes there's a few exceptions but most have a cell wall and some eukaryotes but definitely fewer than prokaryotes the cell wall envelops the cell membrane it protects the cell from changes in osmotic pressure so what does that mean so what you have to understand is that you have different concentrations of solutes so remember solutes are something that's dissolved in a solution so the cytosol has solutes dissolved in it and what happens is if you have different areas of solutes that there's a tendency to want to equal to equalize that imbalance now throw in a semipermeable membrane right so this cell membrane we've discussed is semipermeable things can't just pass in and out you wouldn't be able to control what enter yourself that would make things very difficult so if you have let's use salt as an example sodium ions and you have more on one side of the membrane than the other well the sodium may not be able to pass through that membrane so how do you equalize the concentration well you do that by water flowing from one side to the other and you can affect the concentration that way we'll look at some visual representations of this but just understand osmosis is the diffusion of water to equalize the concentration of solutes we'll talk about diffusion later but in this case it's the water that's moving not the solutes so remember that when we're talking about osmosis it always means that the water is moving not the solutes and then osmotic pressure is the differences in that concentration of solutes on opposite sides of a semi membrane through which the water can pass the solutes cannot so it can be salts sugars etc anytime that they can't pass through the membrane water is going to be the means of equalizing that pressure alright so there's another term that's important for this and it's tonicity so it's the degree to which a particular cell is able to withstand changes and osmotic pressure so what we're looking at if you take for example the cell right we know that there's a cell membrane that surrounds that cell and it's not going to allow things to pass through necessarily some may but most will not so comparing that cell to whatever solution it may be and so let's say for the ease of visualization you take an onion cell and you put it in a beaker of water so you can compare will go back to sodium the amount of sodium inside the cell versus the amount of sodium in the water and the beaker now if there's the same amount of sodium inside the cell and out that would be an isotonic medium right so the solute concentration is the same inside and out so there's no net movement of water it's that there's no need to equalize it there we sell that we want are moving in and water moving down but no net change it's going to stay pretty constant but you could also have a hypertonic medium so that means that the concentration outside the cell is higher than inside the cell so more salt in the water than in the cell which means that we want to decrease the concentration of the salt water outside of the cell which means that water will rush out of the cell to dilute that concentration in the solution right so what's gonna happen well if you have a cell and the water rushes out it's going to shrivel up all right and it can there's a slight difference in what will happen if there's a cell wall present or not if there's only a plasma membrane in no cell wall Kragh nation will occur which means that the cell will become d hi read it it's gonna shrivel up if there is a cell while plasmolysis will occur meaning that the plasma membrane contracts and detaches from the cell wall the cell volume decreases but the overall cell shape stays intact because of that cell wall for a little while anyway eventually the cell will be damaged but it makes it a little bit more resilient than if there isn't a cell wall all right lastly we can have hypo tonic so remember hyper is more so hypertonic medium more hypotonic is less so we're looking at a lower concentration outside the cell then inside the cell which means the water is gonna flow from out into the cell which is gonna cause that swell that cell to swell and it can possibly lyse or burst so when we talk about lice or lysis that means the cell is bursting so again the presence of a cell wall will allow the cell to avoid lysis for some time but eventually still would occur all right so again this is what we're looking at here so isotonic here we're looking at does it say doesn't really say I just but it says the solute concentration is 20% out and 20% in it's the same so water is moving in and out but there's no net change hypertonic solution at the concentration outside is lower than the concentration inside sorry hyper sorry I knew I was saying something wrong sorry it's a hypertonic solution meaning higher the solution outside is higher than inside so we have 40% solute concentration as opposed to 20% inside meaning that water is going to flow out to try to dilute the solution outside and we've hypotonic solution now hypo I got it right this time I pose less and we're talking about the solution so if you ever get confused that's a solution and we're talking about outside all right so in this case high post hypotonic we have a lower solute concentration outside than in water is gonna flow into the cell to dilute the concentration in there the cell is going to swell and possibly lyse all right so this is without the presence of a cell wall this is only a plasma membrane so what happens if there is a cell wall well the net movement everything is going to stay the same but what main change is what happens to the cell inside the cell wall so again isotonic solution there's no net movement nothing's going to happen hypertonic solution we have a concentration higher outside water flows out the plasma membrane and the cell will shrink up the cell wall will retain its shape a little bit so remember that's plasmolysis right so last hypotonic it's lower solution outside than in so water flow flows into the cell to dilute the concentration it's going to swell but the cell wall will help prevent that lysis for a bit all right oops so we're gonna talk about prokaryotes and some of the cell structures now most likely what I'll do for this lecture is I'll get through the end of 3 point 3 which is the prokaryotes and I'll leave the eukaryotic section for the beginning of the next lecture and then we'll move into chapter 4 but I think just with everything to cover I think it's gonna be hard to cram the entire chapter into one leg all right so prokaryotes well we already discussed there's no membrane-bound nucleus but there is a nucleoid which is this region inside the cell it's not membrane bound but you would find the DNA here as well now remember in prokaryotes that's going to be circular chromosome instead of linear chromosomes you're also gonna find nucleoid associated proteins there are Knapp's proteins that aid and the organization of packaging of the chromosome so inside of eukaryotic cells you have histones and they take all that DNA and they packages up package it up so that it's condensed and it's not taking up so much space and so these naps are similar to histones and eukaryotic cells archaea you can find either histones or naps so remember key are usually going to be some sort of an intermediate between prokaryotes and eukaryotes a little bit closer to eukaryotes most of the time but they'll share some characteristics in both all right you also have what are called plasmids so in our body we have chromosomes right we have 23 pairs of linear chromosomes that contain all of our genetic information prokaryotes you have that single circular chromosome which is pretty small in comparison but you have plasmids as that shown on here yep here in there these extra chromosomal so it's DNA it's not part of the chromosome small circular double-stranded DNA there can be hundreds in a bit in a single cell but not all bacteria will have plasmids some well some won't some archaea have plasmids some eukaryotes have plasmids but most commonly you will find them in bacteria so they often carry genes that confer advantageous traits such as antibiotic resistance and they may make the organism more pathogenic right so if you have Staphylococcus aureus right staph aureus if it doesn't have the plasmid for antibiotic resist well it would just be normal staph.aureus right so if you get a staph infection you take antibiotics it clears it up but what if it has the methyl and resistance gene right so you have mersa methyl and resistant Staphylococcus aureus right in that plasmid allows that so that those antibiotics don't work it won't clear up that infectious that's obviously going to be more pathogenic than the version it doesn't have the plasma right we also have ribosomes so remember all living organisms will have ribosomes but there's differences in the size of the subunits so ribosomes have a large subunit and a small subunit and they can be measured using a sped burg unit which means if you put these into a tube you put them in a centrifuge you spin it around things are going to separate out at different rates based on their size and mass so the set fir'd sorry speedbird unit measures that so it turns out eukaryotic ribosomes in measure is 80 said work units prokaryotic ribosomes are smaller at 70s our keel ribosomes are 70s as well so similar size to the prokaryotic but they do have different proteins and different ribosomal RNA that's actually more similar to eukaryotic ribosome so again an intermediate they have the same size as prokaryote but genetically and structurally they're more similar to eukaryotic ribosomes and so if you remember we talked about the genetic analysis that went into [Music] into comparing organisms how genetically related they are in one of the ways that we could one of the the most important ways that we've been able to get much more accurate is by using this ribosomal RNA in these ribosomes if every living organism has to have ribosomes well then that's a great thing to compare to try to determine how closely related they are so these phylogeny is that we were looking at now can be based on the genetic similarities between this ribosomal RNA not necessarily appearances because you would look at an archaea and a bacterium would say oh well archaea is a lot like bacteria but that's not entirely accurate all right so here we have the nucleoid so again it's this kind of loose area inside it's gonna contain the DNA it's going to contain those Knapp's those proteins as well here's the ribosome where I said it is two subunits you have a large subunit a small subunit if you take it together 50s and 30s so combined that comes out to 70s I'm not quite sure on the math on that because it seems like it would be 80s but I think because it's combined it changes the sedimentation rate okay so some of the cell structures that would find in a prokaryotic cell so we said there are the presence of inclusion bodies that are really going to replace some of the normal storage structures we might find in a eukaryotic cell so these are sign of plasmic structures they store nutrients like glycogen or starch which are polymers of glucose or those are other substances and to separate the cytoplasm so it aids and reduction of osmotic pressure so your if you're able to separate off if you have glucose and you can separate it off in like these inclusion bodies then I don't have to worry so much about the osmotic pressure that might put on the cell so there's a few different types of inclusion bodies so first is volitans granules also called metachromatic granules so they store polymerized inorganic phosphate used in metabolism and the formation of biofilms so this is when it's important to remember right so all eukaryotic cells we're talking about some version of glucose whether that's glucose glycogen starch some other sugars but mostly glucose some bacteria will use glucose but some are going to use different items like in this case inorganic phosphate look at iron or iron sulphide they you're able to metabolize those substances to use them for carbon and energy so they wouldn't store glucose they would store inorganic phosphate so an example of this would be the kureta bacterium diphtheria which causes diphtheria so this is again I want to I want to stress this when I include specific examples like this that means you want to know now if you look at the outline there were a few more listed examples I narrowed this down to the ones that I feel are clinically relevant again archaea don't cause any human own human diseases therefore I'm not gonna ask you to memorize that I want to focus on the things that were likely to come up again later in the semester so the example of Alton granules Korena bacterium diphtheria second type of inclusion body sulfur granules so they store elemental sulfur in sulfur bacteria where they use that for metabolism so thio bacillus species are an example of that you have PHP or polyhydroxybutyrate so it's in this case the bacteria is surrounded by a phospholipid bilayer that's embedded with protein they may be used to produce biodegradable plastics so examples of this would be some bacillus species and some Pseudomonas species you also have gas vacuoles which would contain gas in order to change buoyancy of these might of prokaryotes that are living in a water column and so you want to be able to move to where the food is so by adjusting the amount of gas that's in those vacuoles the the prokaryote can move up and down to move to a more favorable location right look at it this way if you have two archaea that are both in a water column and they're competing for the same food source and one can move up and down and one cannot it's going to provide a an advantage for the one that can't move because it can move away from competition they can move to new areas it can be a valuable ability for these prokaryotes you also have magnetic inclusions these contain Magneto's ohms which contain magnetic iron oxide or iron sulfide surrounded by a lipid layer and it allows the bacteria to align along the magnetic field it allows you if carboxy some inclusions it has an outer shell of protein subunits it's and it could be filled with Rubisco I'm not going to ask you to memorize this I just include it to have all the information there but I'm not gonna ask you to memorize ribulose 1.5 biphosphate carboxylase kind of outside the scope of this but Rubisco is an enzyme that you've probably actually encountered in biology before alright so again stores the carboxyl some stores for carbon metabolism all right so here's just some looks like electron photographs of different inclusion bodies I'm gonna skip over that but they're here if you're curious alright so another thing that's important about prokaryotes is their ability to form endospores now typically when we see bacteria it's gonna be in a vegetative cell which means that it's enzymatically active it's it's ready to reproduce it's ready to do everything normal bacteria would do but we touched on this before if the environment becomes unfavorable right it's dehydrated there's no water available maybe there's no more glucose or whatever the carbon and energy source may be for that bacterium you have a choice you can die when everything when all the water and food is gone or if your gram positive bacteria and you're able to form an endospore well you undergo sporulation you form this inactive structure it's no longer enzymatically active all it's doing is surviving it has this shell that prevents it from drying out it prevents it from sometimes from radiation damage from radiation from antibiotics from disinfectants makes these really really resilient that they can survive in that and sometimes the environment for up to a thousand or more years and then once they're put into a favorable environment where there's water and food they'll reactivate will form a new vegetative cell and though and they'll pick up where they left off so it's really an important evolutionary adaptation for these to be able to survive in harsh environments extreme temperatures I left that out there a little sometimes survive more harsh temperatures for the vegetative cell so why is that important well Clostridium botulinum right it's a toxin that causes botulism it's found often in like canned goods that are dented or sometimes if it's like a potluck where people can at home and they didn't sterilize properly so right most bacteria you put in boiling water they boil it for 15-20 minutes it's gonna kill most everything these spores may be not right so especially like the Clostridium spores other end of spores can be very heat resistant so let's say you only boil for 15 minutes and it's not long enough to kill the Clostridium botulinum spores well then when you can it they're going to be able to grow so another reason why these endospores are important so most of the clinically significant endospore forming gram positive bacteria are bacillus species and Clostridium species then I mentioned this and I just put it here again only gram positive bacteria can be endospore formers there are no gram negative that that form endospores so these bacillus species and Clostridium species have listed a few here that are important so bacillus anthracis causes anthrax and the spores can survive for many years the matter of fact if you garden your you're most likely exposed to bacillus anthracis spores in the soil they're common in with animals like horses matter of fact there was some cases where they used to use horsehair brushes to shave that the spores were in that horse hair and when you when the person shaved and had a cot the spore got in the cut and caused cutaneous anthrax but commonly found but in lower amounts it's less likely that the spores will cause disease but they also have to get into either your lungs or a cut type of thing all right Clostridium tetany causes tetanus so again you step in a rusty nail it's not the rust on the nail that's the problem it's the Clostridium Tet 9 spores that are on the nail and you have a puncture wound it introduces those spores deep into your tissue in an anaerobic environment and they can start to grow and they produce a toxin that causes tetanus Clostridium difficile causes pseudomembranous colitis c-diff is probably the way you've heard it right so we all have clustered him difficile in our intestinal tracts and our digestive tract but if you go into the hospital and let's say you're on a strong dose of antibiotics for a long period of time well not only does that kill a potential pathogen it tends to also destroy the normal flora the normal microbiota of our digestive tract but if you have something in there that can cause that can form spores like cluster M difficile does those antibiotics hit kills everything Clostridium difficile forms endospores then once the antibiotics are gone they form vegetative cells they start to grow now there's no competition there's because because your normal microbiota is gone and they're able to grow unchecked so it would be an example of an opportunistic pathogen here and they cause pseudomembranous colitis which causes remember quickly about 17,000 deaths a year in the United States so everybody knows the scary pathogens but things like this are actually much larger cause than what people typically worry about all right clustering perfringens causes gas gangrene and Clostridium botulinum causes botulism and the toxin the Clostridium botulinum toxin is used for Botox that's a paralytic agent so when they inject it into you let's say the area above your face it paralyzes the art sorry in your face above your eyes it paralyzes those muscles so that you can you know to help prevent wrinkles so keep in mind that's what you're doing if you get Botox injections all right so some of the characteristics of vegetative cells versus endospores vegetative cells are sensitive to temp temperatures and radiation they may be gram positive or gram negative they have a normal water content normal enzymatic activity they're capable of active growth and metabolism endospores are resistant to extreme temperatures and radiation they do not absorb grande stain so only endospore stains so we talked about that we have to use Heat you drive this the I mean drawing a blank malachite green dye into the end of Spore if you don't it'll just appear as a clear area and again only found in gram positive bacteria they're dehydrated they have no metabolic activity they're dormant there's no growth or metabolic activity again once conditions become more favorable the end of spores will wake up and become vegetative cells all right so here the process of sporulation the so again you have cluster diem difficile DNA the you're exposed to antibiotics the bacteria senses this it's going to replicate the DNA and one of those copies is going to move to the end of the cell you know have membranes that form around the DNA this is gonna form what becomes what's called a force for it's gonna form some more membranes and then this protective cortex is going to form around the spore and then it's gonna form a protein coat around the spore and the spore can then be released from the vegetative body so remember when you look at this it's hard to see in here because it's so small but you're gonna have a lot of these spores are found inside the vegetative cell but some of the spores will actually be outside of the vegetative cell all together alright so another so we're continuing with the structures in prokaryotic cells you have the plasma membrane and it's part of what's going to be outside of the cell so let me go back here for just a moment alright so just to give you a visual idea of this you have the plasma membrane so remember every living organism is gonna have a plasma membrane something that's gonna separate the contents of the cell with the exterior of the cell but in prokaryotes a few eukaryotes and some archaea you have a cell wall as well it's gonna provide some additional structure for the cell and it's important to what part of the reason why is while eukaryotic cells except for some single-cell organisms you have the support of the rest of an organism but if you're a single-celled prokaryotic organism you don't have those other tissues the other structure protect those cells they have to exist on their own so a cell wall helps protect that cell and then as some of them you're gonna have another layer called a capsule and so we'll look at some of these as well you're also going to have these proteins that come out of the self Embree a you can have pillows or pillow and flagella or flagellum as well and those are what we're gonna look at in coming slides but as we do so I wanted you to have an idea visually of what it is we're talking about alright so again you have the plasma membrane but you have what's called cumulatively or collectively the cell envelope so that's all the structures that collectively enclose the cytoplasm and internal structures of the cell so going back we could consider the plasma membrane the cell wall in the capsule all to be part of that cell envelope okay so I just want to make sure you understand that that's referring to the cell envelope could just be the cell memory if there's no cell wall it could be the cell wall and the plasma membrane it could be the cell wall the plasma membrane and a capsule those could all sell cell envelope could be any of those right so the plasma membrane as we said gonna exist in all of these it's also called the cytoplasmic membrane or the cell membrane all cells have it it's selectively permeable it's typically going to be a phospholipid bilayer with esters and proteins now the only reason I included this esters is when we get to archaea we're gonna talk about an effort linkage versus an ester linkage so don't get too caught up in that it's just there for comparison fluid mosaic model is a way of looking at the plasma membrane in that it's not a rigid structure it's constantly changing components can move fluidly within the plane of the membrane so you'll have some transmembrane proteins that cover the entire phospholipid bilayer you're gonna have some proteins that are attached to the outside that can move around so that's we'll talk about that really it's just that the components are constantly moving and I'll show you a diagram of that just a moment alright so the Archaean as i said it has an ether linkage instead of an ester linkage if you want to get into the chemistry the biochemistry you can let me know in office hours we can talk but just know a third versus Esther it has branched chains versus straight chains and in some cases may have a mono layer or also a bilayer right you also have photosynthetic membrane structures so why why are we talking about that of course there's photosynthetic structures we know that but why is it why do we need to talk about it in a prokaryote well it goes back to there aren't any membrane bound organelles which means there can't be a chloroplast so we know there are photosynthetic prokaryotes so how do they undergo photosynthesis well they have an in folding of the plasma membrane and inside of that there are photos the photosynthetic pigments like green chlorophylls or bacteria chlorophylls and they replicate the function of a chloroplast so if we were to talk about the electron transport chain that occurs in mitochondria well we know there are heterotrophic bacteria so same thing occurs you have an in folding of the plasma membrane so that you can use that membrane to to complete the functions of the chloroplast or the mitochondria all right so here we have a diagram of the bacteria on plasma membrane so again you have this your phospholipid bilayer you have these phospholipids the head faces out the tails in they prevent this is where you have that semipermeable membrane for things to get through here they would have to be nonpolar and very small to be able to just pass between these molecules so it controls what moves in and out of the cell does that by using protein channels transmembrane proteins as I said you've got these peripheral proteins that can move around on the outside you have glycoproteins glycol lipids that help identify the cells have a couple of attachment and I'm not going to ask you a lot of questions on this it's something you should have covered in a and P or Tenten but it's important for especially these protein channels and transmembrane proteins for some of the things we're going to talk about in just a moment all right so remember their membrane transport systems so you have two types you have passive transport which doesn't require any energy and we'll talk about how that works but that's the big thing no energy it doesn't require ATP so you remember that and then active transport which does require energy in the form of ATP for passive transport there's two types there's simple diffusion so we talked about osmosis right what happens if you have a gradient of solutes where one like one area is higher than the other but if there's a membrane separate separating those only water can move through but if the solutes themselves can pass through the membrane then what's going to happen is they will flow from an area of high concentration to an area of low concentration so I'll go to the next slide and then I'll come back so if you have simple diffusion this is what's happening so again we'll use sodium as the example so you have this higher concentration gradient of sodium on one side of the membrane as opposed to the other so over time what's going to happen is sodium is going to diffuse through the membrane until you have an equal amount of sodium on either side so it doesn't take any energy it's going to move against the gradient from an area of high concentration to an area of low concentration so the difference between this and osmosis is the solute can move through the membrane if it couldn't then osmosis would have to occur right where water would flow from this side to this side but simple diffusion the solute will travel through the membrane and equalize right you also have facilitated transport or facilitated diffusion so if you have a molecule that's too large it can't move across that selectively selectively permeable membrane well then what you is an integral or a carrier protein which is a transmembrane protein so here you have this protein channel that crosses through and these are highly specific so in this case again we'll use sodium just to keep things consistent but in this case the sodium can't go through the membrane on its own it has to go through this channel so you have a higher concentration gradient here lower here so the sodium is going to move through the channel to the other side until you get equilibrium and that's facilitated diffusion now again this requires no energy it doesn't require ATP it's going it's using the concentration gradient to drive it to equilibrium alright last we have active transport as I said this requires energy in the form of ATP it also requires a carrier protein just like facilitated transporter diffusion what's important about this is that using ATP you can pump solutes across the gradient across the gradient so you know if you have let's say you have a higher sodium gradient on the outside than you do inside well you can use ATP energy and pump sodium into the higher concentration right it's sodium doesn't want to go there because there's more on that side in the air but using the energy from the ATP you're able to pump more across so this is the sodium potassium pump we're looking at which UV had an enemy in Physiology when we looked at in muscle contraction and neuron function after the depolarization of the membrane you have all the sodium inside the cell that you have to then get outside the cell so using ATP you pump the sodium out and you pump the potassium back in so that's an example of active transport the sodium potassium pump alright so this one is going to be very important one of the first things we've stressed right is when we look bacteria we are looking at grand positive versus gram-negative bacteria so what makes them different we touched on it a little bit when we went through the Gram stain right thick layer of peptidoglycan which is is the gram positive versus the thin layer versus gram negative and there's a few other differences so this is you're going to see a handful of questions right from here this is important you're gonna need to remember this for the rest of the semester because this is only something we're going to talk about all right so gram positive again thick layer of peptidoglycan also known as murine it's 30 to 100 nanometers thick and you have long chains of alternating molecules of n-acetyl glucosamine or ma g and n acetyl Meramec acid ER and a.m. for gram-negative you have a thin layer of peptidoglycan 4 nanometers and then the same chains of alternating n AG and n am so let me look at that and I'll come back to this alright so this can be this one can be a little bit confusing we haven't talked about these cross linkages yet which is the difference but what you're seeing here represented is the blue is your n acetyl glucosamine and the orange is your n acetyl Meramec acid so you basically have these two different polymers they alternate and if you want to think of a way to understand it picture two-by-fours in your wall right and maybe that's your n AG and then you can have cross braces which are your n am it it creates this lattice so our a mesh right so the cell wall has these alternating polymers that create a mesh that that creates the cell wall that provides structure for the bacteria will touch on these these cross linkages as well the case of grande positive you have these Penta cycling cross bridges and I'm not going to ask you to remember Penta cycling or say Penta glycine but you want to remember cross bridges versus gram-negative where you have direct cross links [Music] so here you have these I don't want to get into this too much I really don't want it to be overwhelming all I want you to remember is the cross bridges versus cross-linked you be good I'm not gonna stress that even that much this first parts more important and the rest of this I expect you to know that don't get too hung a button on that second unit all right for gram-positive you have another substance called T Co ik acids that are embedded in the cell wall you would not find echoic acids and gram-negative gram positive bacteria for the family mycobacteria a CA you have another external layer of waxing mycolic acid so remember we talked about acid fast staining and you're looking to see if there was mycolic acid present or not again just like endospores the only time you're going to find these is in gram positive so all Mycobacterium all acid fast positive bacteria are going to be gram positive all right so back to gram negative gram negative will have what's called a periplasmic space that's filled with a gel-like substance it will also have an extra outer membrane it's a second lipid bilayer it's external to the peptidoglycan and it's attached by a murine lipoprotein last you have a lipopolysaccharide or LPS which is contained in the outer membrane not the outer membrane the outer membrane it's an endotoxin and it's composed of three parts lipid a a core polysaccharide in a no side chain now this causes fever hemorrhaging and septic shock so those chain antigens and look at that in a moment can be used to identify specific strains of bacteria such as a coli o157 h7 when you talk about there's an e.coli outbreak most likely it's this strain oh 157 h7 we all have e.coli in our digestive tracts as long as to stop this pathogenic version it's not going to make you sick okay so let's look at some of these things we just talked about so we already covered gram-positive again alternating units of n AG and n a.m. in both of these it's going to be a thicker layer of peptidoglycan and gram-positive and gram-negative you're going to have these pentapeptide cross-bridges versus direct bridges gram-positive you have Toccoa Cassatt which you would not find in gram-negative here's your thick layer of peptidoglycan versus your thin layer you have your plasma membrane in both cases your cytoplasm in both cases but now when we come over to the gram-negative you have the LPS or the lipopolysaccharide and that's made of this outer portion as your o antigen u lipid a or your lipoprotein lipoprotein now remember an antigen is a portion of a molecule that an immune cell is going to recognize either a self or as like a foreign object so we'll talk about antigens it's a portion of that in this case the Oh Porsha of this LPS is is an antigen and that's part of what causes when it when the cell breaks down and that o antigen is released your body has this large immune response because it recognizes this as a foreign foreign molecule so you can have a fever in an immune response and if it's strong enough you're gonna have toxic shock syndrome you also have this periplasmic space where it's filled with a gel-like substance you do not see it here alright so grand positive thick peptidoglycan gram-negative thin - koch acid and Michalek acid you could find in gram positive you won't find it in gram negative gram negative you're gonna have a pair of plasmic space you're also gonna have this lipopolysaccharide or LPS all right so let me talk about Gram stain and really quick so remember when we talked about Gram stain we talked about the crystal violet we so for both of these we applied crystal violet it's gonna be absorbed it's gonna stain the cell green or I'm sorry purple there no we're green came from alright and then you're gonna add the grams iodine the mordant and it's going to create a complex between the gram grams iodine and the crystal violet right it's gonna make it bigger it's gonna make it harder for it to leave the cell but this thicker peptidoglycan layer is going to hold it in much more efficiently in this thin layer so then we we decolorize but it doesn't really do anything with a gram positive because it's it's held in but it's gonna rinse it decolorize it and rinse it out of the gram negative then when we add the safranin it's gonna stain this pink this will stay purple because you still have the grimms crystal violet inside the grande positive cell so just another way of looking at that hopefully you can start applying these from from different perspectives so we talked about acid fast staining so remember we were looking for the president of mycolic acid which is a waxy substance so we need heat to drive in the stain in this case I was a caramel fusion I believe yeah caramel fusion drives it in and as fans bacteria will retain that stain the non acid fast cells it'll rinse out and then when we apply safranin I'm sorry um it's the blue sorry I can't remember the counter staying off the top of my head but anyway it'll stain it blue so the mycolic acid in this case is the differential that we're looking for like the waxy mycolic acid again only in gram positive all right so we also talked about this lipopolysaccharide or LPS and remember we said there's three parts so there is the O antigen this is the part that it's gonna cause that immune response in the body the core and a fatty acid archaea cell walls do not contain peptidoglycan but they have a similar polymer called pseudo peptidoglycan or pseudo marine in which the NA M is replaced by a similar subunit they may also have a layer of glycoproteins or polysaccharides that serve the cell wall rather than pseudo peptidoglycan and there's a very few archaea that may lack cell walls entirely all right so back to the cell envelope there may be another layer called a glycocalyx or a Ness layer so most prokaryotic cells have cell walls but some may have additional cell envelope structures exterior to the cell wall and that can be one of two things here it can be a glycocalyx or it can be an S layer both cases is a sugar coat it's external to the cell wall and it helps that bacterial cell to adhere to surfaces or other cells it also aids in the formation of biofilms and it provides protection from predation and the action of antibiotics and disinfectants so let me come back to this right so remember we have the plasma membrane we have the cell wall in most instances in prokaryotes and then we might have this capsule it's an additional layer remember we talked about negative stains so you could visualize capsules I'm gonna show is these clear areas and also hopefully you remember that I mentioned that it's an indication of increased pathogenicity if there's a capsule it's much more likely that it's a pathogenic strain biofilms are they're like little cities of bacteria microorganisms they all live together in some cases you you're gonna have a layer closest to the surface and then more layers above it that are different species and in a lot of cases the byproducts of one species are are used by another species to metabolize and then the byproducts of that species are used to metabolize another they all create this little ecosystem those layers make it very difficult for things like antibiotics or disinfectants to penetrate all the way to the bottom so they provide protection and again a lot of times they work together and they're very efficient at holding water so it prevents these biofilms from dehydrating so I bring that up only just because we've talked about that these this glycocalyx aids in the formation of these biofilms so there are two types of glyco calluses a capsule or a slime layer they're very similar the capsule is going to be a much much organized of the two it's another layer outside the cell wall it's composed of polysaccharides of proteins it may contribute to its pathogenicity and makes it more difficult to immune cells to phagocytize or engulf the microbe so example that would be streptococcus pneumoniae and so a lot of times if you're looking if you took a sputum sample let's say that clinical clinical case we were looking at you took a sputum sample and you put it on a slide you stained it if there's a presence of capsules then it makes it more likely streptococcus pneumoniae is there which is gonna be more pathogenic it could also be a slime layer which is less tightly organized let's let it's more loosely attached to the cell wall so it can be more easily washed off it may be made of polysaccharides glycoproteins or glycol lipids so in so other than glycocalyx you can also have an S layer and it's another structure it's composed of structural proteins and glycoproteins it's found many times outside the cell wall bacteria but at times it can act as the cell wall for archaea it's not very well understood how these work but they may protect against osmotic pressure x' and interact with host immune cells all right so again that's what we're looking at here is the capsule okay so it's the last part we're going to cover is going to be filamentous appendages so many bacteria have protein appendages that can help in attaching to surfaces they can aid in the transfer of DNA from one bacterium to another or they can be used to provide movement so fimbriae and pill I to of the ones we're gonna look at it very structurally similar and they can be difficult to tell apart so sometimes fimbriae and pilla are used interchangeably but in general fimbriae are short bristle like proteins they project from the cell surface and there's often hundreds of them so again they aid in attachment to surfaces and other cells you can also have a pill i which is singular or pilis i'm sorry pillows pillows a singular pillow is more than one so the pillow are typically going to be longer fewer than the fimbriae but also aid and attachment to cells there's a particular type called F pilis which is also called the sex palace that's involved in the transfer of DNA between bacterial cells so if you have bacteria in close quarters they they can connect via these fpy and they can exchange bits of the chromosome back and forth or plasmids back and forth so sometimes when you talk about or you hear about a new species acquiring antibiotic resistance it could be because the that plasmid is transferred from one species to another all right you have a flagella or flagellum which our structures used by cells to move in aqueous environments they act like propellers so the example I used for that before was it's similar to a sperm if you ever seen a video of that moving waves the tail is able to move throughout an aqueous solution so there are four types of arrangement for the flagella first mono trick is it means there's a single flagellum and it's typically polar meaning that's located at one end or the other so the example of a sperm is this is exactly what I would name right one flagellum on one end example that would be Vibrio cholerae which is a gram-negative and it causes cholera you can also have an vitreous which means it has a flagellum or Tufts of flagella at each end at both ends so spur a minor which causes spur Allari or asian rat bite fever or sodoku you can have low fat rickets which means the cells have a tuft of flagella at one end an example will be Pseudomonas aeruginosa which is an opportunistic pathogen it causes swimmers ear burn infections and other infections as well last we have parrot rickets which means there's flagella that cover the entire surface of the bacterium and e-coli would be an example of that all right let me I think so mono trick is you have one flagella on one end and Patricius you have one flagella or Tufts of flagella at both ends Lofa trick is you have the tufts at one end and para trick is which is covering the entire bacteria all right here you have an electron micrograph of pill AI you can see here right these two bacteria are XJ they're connected via that F pill I and that might not be as sex pillow so disregard that so they definitely have the pill I I'm not sure if they're the SEC's pillows or not so you'd see example the pill on here so jealous structures of the grand positive or negative bacteria I left this in but you might note I skipped over that part of the outline I'm not going to ask you about the differences between the base on this I don't think it's really worth our time in a chapter that's going to take a bit to get through anyway but you can see how they're attached and how the flagella motion works alright last a little more information on these filamentous appendages so how do they move well there's a few different types of movements so they can respond to a variety of environmental signals which can be positive meaning moves toward the signal or negative where they move away from the signal and you get a phototaxis which means that the bacteria or the prokaryote moves toward or away from light you can have magneto taxes or they're gonna move along the magnetic fields can have chemotaxis where they move along chemical gradients an example might be if there is glucose available right then the bacterium may want to move toward the glucose where there's a higher concentration or it could be a high gradient of antibiotic where the bacterium would want to move away from that substance the way that they do that is look through what's called run and tumble so it can be random or directional to be more directional so what the bacterium is going to alternate between these periods of tongue run and tumble which means that when the flagella rotate counterclockwise the bacteria is going to run when the flagella rotates clockwise it's going to tumble meaning it's really going to be more random but it's going to turn in a certain direction when it's running that's going to move along as a longer straight line so to give you an idea of what that means so here so you have the flagella rotating clockwise and it's more turning movement versus counterclockwise where it's more directional movement running so the bacterial counterclockwise it would run it's going to move straight then it's gonna tumble it's going to clockwise rotation it's going to turn then you're gonna go to counterclockwise rotation and it's gonna run and so how much it alternates between these two is going to determine whether it's a more random movement or more directional movement all right so the clinical case study update will cover this then we'll wrap it up and then in the next lecture we'll pick up with three point four and move into Chapter four and so after diagnosing Barbara with pneumonia the PA writes her prescription for amoxicillin commonly prescribed type of penicillin derivative more than a week later despite taking the full courses directed Barbara still feels weak and is not fully recovered although she was able to get through her daily activity Shira Marin returns to the health center for a follow-up visit so many types of bacteria fungi and viruses can cause pneumonia amoxicillin targets the peptidoglycan and bacterial cell walls and since it hasn't resolved Barbara symptoms the PA concludes it's probably not bacterial because it probably doesn't have peptidoglycan so the pathogen could be a virus a fungus or a bacterium that it doesn't have peptidoglycan or it could be resistant to obnoxious illah so how can the PA definitively identify the cause of Barbara's pneumonia what form of treatment should the PA prescribe given that the amoxicillin was ineffective so there's a few things you could do at this point you could again take a spoon and say sputum sample and culture it and then test it for an abaya antibiotic resistance right at which case or antibiotic susceptibility so you would grow it and expose it to different antibiotics and determine are any of those effective in treating it now that would be the case it was a bacterium obviously if it's a virus it wouldn't grow on auger and and you wouldn't be concerned about but if it's a bacterium you would want to determine is it is it responsive to any antibiotic treatments if it's viral you can look at antiviral medications so you would want to culture and determine what is caused in the disease at this point all right it could also provide a broader spectrum amoxicillin or I'm sorry broader spectrum antibiotic to see if that was effective so when we come back from the next lecture we will touch upon that so the rest of chapter 3 point 4 and chapter 4 will be posted on Wednesday thank you