hey everyone Dr D here and in this video we are going to be covering chapter nine from our microbiology ass systems approach 7th edition this chapter covers microbial nutrition and growth so let's go ahead and get started Dr D Dr D Dr D Dr D Dr D Dr D Dr D Dr D Dr D explain stuff all right let's get started with this exciting chapter covering microbial nutrition and growth so just like you and me we need nutrients in order to grow microbes are no different they need a source of nutrients in order to grow and develop and to divide and so this chapter talks about the different microorganisms and where they obtain their nutrition from so first of all what is nutrition Nutri nutrition requires nutrients nutrients are are acquired from the environment and used for cellular activities these activities like I said include growth and Divi division organisms require a constant influx of certain substances from their habitat to fulfill their dietary needs and the source of the particular elements their chemical forms and how much of the element is needed very iies among different types of organisms we're going to be talking about the different elements the different molecules the different nutrients that these organisms need in order to grow and here you can see a list of different elements from you know the periodic table of elements you know we have different elements that are required by all living organisms carbon hydrogen oxygen phosphorus potassium ium nitrogen sulfur and so on and so forth there are also a host of other elements that we need ENT Trace Amounts in minute amounts as well so we're going to talk about these different elements we're going to talk about which one of these which ones of these elements make up our biomolecules and you know where we Source these from and where microorganisms Source these elements from so again we have certain nutrients that all organisms require essential nutrients are substances that must be provided to an organism for instance all organisms require carbon hydrogen oxygen nitrogen phosphorus and sulfur all organisms require these handful of elements because these are the central elements to our major bio molecules and I'll show you what the biomolecules are in a little bit macronutrients refer to the nutrients that are required in relatively large quantities so for instance carbon hydrogen oxygen nitrogen phosphorus and sulfur are all macronutrients micronutrients on the other hand also known as Trace elements are required in small amounts or minute amounts so for instance you know you require copper zinc uh you require iron in your diet these would be Trace elements required and a lot of times these Trace elements they serve as co-actors they are involved in enzyme function and maintenance of protein structure so for instance uh remember what a co-actor is a co-actor is an enzyme helper or a protein helper a co-actor binds to an enzyme or a protein to allow it to function correctly so for instance hemoglobin in your blood requires the co-actor iron in order to properly transport oxygen inorganic nutrients as their name suggests are nutrients that lack carbon organic nutrients these are nutrients that contain carbon Plus hydrog nen common inorganic nutrients are elements like iron zinc sulfur pottassium common organic nutrients include things like vitamins or growth factors here we can see some of the principal inorganic elements and their reservoirs their reservoirs mean where they obtain their elements from so organism can can obtain their carbon either from the air in the form of CO2 or from rocks and sediments organisms can obtain their oxygen either from the air certain oxides and water so I'm not going to go through this entire list but it gives you an idea of where microorganisms can obtain their elements the reservoirs that Harbor these elements and where they can obtain these elements now what is the chemical composition of a bacterial cell because by looking at what a bacterial cell is comprised of we can glean we can understand from that the nutritional requirements of that bacterial cell well it turns out about 70% of the cell content is water and that makes sense most of your body body weight is water as well and then the proteins are the next most prevalent chemical so when we subtract the water weight of a cell this is the remainder is known as the dry cell weight imagine taking a bacterial cell and completely dehydrating it removing all water well you would remove 70% of the bacterial cell's weight but what's left over is the dry cell weight and 97% of the dry cell weight is composed of organic compounds this means the molecules that have carbon and hydrogen as well now 96% of the dry weight is composed of only six elements remember remember these six elements I call them Chomps right um carbon hydrogen oxygen nitrogen phosphorus and sulfur these these six elements alone make up 96% of the dry weight of the cell and that's why these are definitely macronutrients nutrients that are required in relatively large amounts by the cell again proteins make up only 15% of the total weight of a bacterial cell such as aaricia coli but it makes up 50% of the dry weight of the cell RNA makes up 20% of the dry weight DNA makes up 3% of the dry weight of the cell carbohydrates make up 10 lipids make up 10 and then miscellaneous make up the remainder four these are the organic compounds so by the way these these major organic compounds are known as biomolecules protein means RNA and DNA by the way the RNA and the DNA are known as nucleic acids then you have the carbohydrates and the lipids these are biomolecules and the biomolecules make up the majority of the dry weight of the cell what about inorganic molecules inorganic molecules only make up about 1% of the total cell's weight while water remember makes up 70% of the cell's weight water is abundant in all living cells again we can have a breakdown on the right here of various elements and their contribution to the dry weight of the cell remember the macronutrients the macronutrients are required in relatively large amounts in the cell while the micronutrients are required in lower quantity in the cell a major way that organisms are categorized based on their nutritional requirements has to do with where they obtain their carbon this is known as their carbon Source consumers like you and me are known as heterotrophs because we obtain our carbon from organic compounds that we ingest just think about it where do you think you get your carbon from remember we need a large source of carbon in our nutrition in our diet because carbon is the most abundant element in our dry mass of our cells so where do we get our carbon from well don't we eat breakfast lunch and dinner we obtain our carbon from our diet from things we eat organic molecules that we consume so these Organisms that get their carbon from organic molecules they consume are called heterotrophs so you and I we are heterotrophs we obtain our carbon from organic molecules and this means that we are dependent on other life forms we cannot feed ourselves we need to consume other organisms to obtain carbon molecules conversely autotop are organisms that obtain their carbon from CO2 from the air there is CO2 floating around in the air and autot tropes can actually capture inorganic CO2 as their carbon Source that's where they get their carbon from it's a process known as carbon fixation if any of you have studied photosynthesis in the past you know that that During the Calvin cycle CO2 is captured from the air and that's known as carbon fixation so can you and I let's see if you can beat Wicket can you and I undergo carbon fixation can we take CO2 out of the air as our source of carbon that's right wicked wicked is so smart um we cannot right because you know this is what plants do plant have chloroplasts they've got the ability to capture CO2 right and photosynthetic organisms can capture CO2 from the air they are autot tropes and because they can capture CO2 from the air and they don't require other organisms they don't have to eat other organisms they're known as self feeders these are the producers in the environment in ecology when we're talking about the ecosystem the autot tropes are the self feeders they don't have to consume other organisms to live and because of that they tend to be producers they are at the bottom of the food chain they're they're the source of the organic molecules for the rest of us us heterotrophs and once they obtain that CO2 they can convert that CO2 into other carbon compounds like sugars or different biomolecules without these autot tropes we would have nothing to eat the food web would collapse the ecosystem would have no way of sustaining itself and it would collapse the autot tropes are at the bottom of every food web and they are the producers in the ecosystem so without autot tropes there would would be nothing for heterotrophs to consume and we would perish as heterotrophs now moving on to nitrogen sources remember nitrogen is another macro element that microorganisms need in large amounts nitrogen can be sourced at from the air some organisms these are known as nitrogen fixers some organisms can actually take n nitrogen from the air and that's a good resource and the air is actually a great source of nitrogen seeing as how 79% of the atmosphere is basically made up of nitrogen so some organisms can actually capture nitrogen from the air and these are known as nitrogen fixers now you and me we obtain our nitrogen from our diet we consume other organism so we're eating their proteins their DNA their RNA their ATP and that's where we Source our nitrogen and now what about microorganisms such as eoli where do they get their nitrogen from well some bacteria and algae utilize inorganic nitrogenous nutrients such as NO3 minus this is nitrate NO2 minus this is nitrite or NH three this is ammonia these are three common sources of nitrogen for microorganisms so if you can't fix nitrogen from the air you can always gain it from your environment in the form of these three molecules these three inorganic molecules next what about oxygen sources where do we get oxygen from well first of all oxygen makes up 20% of the atmosphere so that's one source of oxygen but also from your your diet or from the environment as well how about hydrogen sources well we can get hydrogen from the our diet from biomolecules that we consume plants get their hydrogen from water they can actually remove hydrogen atoms from water molecules and hydrogen is important in oxidation reduction reactions in the cell such as photosynthesis and cell ular respiration without hydrogen without access to easy hydrogen elements photosynthesis and cellular respiration would not be possible what about a phosphate Source or phosphorus Source where do we get those you and I obviously get our phosphorus from our diet the molecules we eat but there are other inorganic sources of phosphate so for instance in mineral deposits from soil and such microorganisms can obtain their phosphate from their environment in the form of these of these deposits and what about sulfur remember sulfur is a macronutrient as well well it's widely distributed throughout the environment in rocks and sediments so it's it's easy to find it in the environment it is an essential component of vitamins such as Vitamin B1 and it's required in two of the 20 amino acids methionine and cysteine what about essential organic nutrients remember I said organic nutrients include the vitamins and the growth factors so these organic nutrients uh such as amino acids nitrogenous bases vitamins that cannot be synthesized by an organism they must be provided by the environment now another way that organisms are categorized based on their nutritional types is how they get their energy Organisms that get their energy from sunlight are known as photot tropes while organisms that obtain their energy in the form of chemical compounds either organic chemicals or inorganic chemicals that they consume these are known as chemot tropes so let me ask Wicked let's see if you can beat Wicket which one are we are we photot troes or chemot tropes that's right as always Wicket we are chemotrophs we are uh organisms that obtain our energy from chemical compounds that we consume and so heterotrophs tend to be chemot tropes for the most part we are chemot tropes we obtain our energy from chemical compounds that we consume photot tropes on the other hand these would be your photosynthesizers these would be organisms like cyanobacteria algae plants trees photosynthetic organisms these are the organisms that obtain their energy from sunlight so let's bring these Concepts together then what do you think a photo autotrof is well remember let's break down this term photo means an organism that obtains its energy from sunlight and auto means an organism that obtains its carbon from CO2 so a photo autotrof would be something like a plant or a cyanobacteria or algae an organism that obtains its energy from sunlight and its carbon from CO2 what about a chemoheterotroph a chemo heterotroph remember chemo means an organism that obtains energy from molecules that it consumes and heterotroph means that it's an organism that obtains its carbon in the form of organic molecules so a chemoheterotroph gets its energy from molecules that it consumes and a heterotroph is an organism that contains its carbon in the form of organic molecules did you know that there are organisms that can mix things up a little bit so for instance a chemo autotrof uh a chemo autotrof would be an organism that gets its energy from molecules that it consumes but autotrof refers to an organism that gets its carbon from CO2 there are microorganisms that can do this there are chemo organic autot tropes and chemol litho autot tropes as well chemo organic autot tropes use organic compounds for energy but inorganic compounds as a carbon Source while chemol litho autot tropes require neither sunlight nor organic nutrients and rely totally on inorganic materials how can they do that they can remove electrons from inorganic substrates such as hydrogen gas hydrogen sulfide sulfur or iron so the point of this slide is to show you that there is quite a diversity in nutritional types so just because you know you're familiar with plants and animals that doesn't mean that all organisms uh especially microorganisms behave in the same way there are organisms that are quite diverse in their nutritional requirements they can get their nutrition in very distinct and different ways energy cannot be used in the form of sunlight or these chemicals like sugars and fats so organisms undergo a process known as cellular respiration oftentimes aerobic cellular respiration you may have heard you may have learned about this in biology 1406 this is the process by which glucose and oxygen become CO2 water and ATP energy microorganisms use oxygen in this process and some microorganisms can use a molecule other than oxygen in this process as well either way this is the process by which many animals protozoa fungi and bacteria obtain their ATP and remember ATP is the energy currency of the cell now when an organism is considered a saprobe or a saprobic organism these are known as the decomposers these organisms can decompose plant litter animal matter dead microbes anything that's dead organic matter these organisms are important for recycling nutrients in the environment in the ecosystem usually when we're talking about sapes these decomposers we're referring to bacteria and fungi fungi are probably the best known sapoe organisms the way these organisms work is that they cannot engulf the large organic molecules instead they release enzymes that break down that organic matter and then they transport the broken down organic matter into the cell here you can see what I'm talking about this is a bacterial cell or a fungal cell this is a sap robe right here in green this is a decomposer this out here represents the organic debris large organic debris now again the bacteria will feed on this debris but the bacteria can't internalize these large pieces of debris so what the or what the organism does is it releases these hydrolytic enzymes enzymes that are capable of breaking down organic matter and then transport these broken down nutrients into the cell so you see you can then absorb those raw components those sugars those fats those nucleic acids those amino acids Etc into the cell and this this is how decomposers work many of these decomposers are obligate sapes which means they must feed off of dead organic material however some of these organisms can be facultative parasites which means that they are capable of feeding off a host think of a fungal infection right there are human fungal infections in that case the fungus is a parasite on you the host that's what a parasite does a parasite becomes dependent on the host for its nutrition so when I say parasite think of something that becomes dependent on the host on which it lives for its nutrition parasites again they live on or in the body they can cause some degree of harm different parasites can cause different degrees of harm some parasites you may not even know they're there like a tapeworm but it still causes harm because it completes nutrients from the host and you know it also inserts its uh hooks into the gut lining which can cause an infection so you know a tapeworm is one of the more mild parasites but then there are parasites that cause a lot of damage a lot of disease and can cause death even hi Gizmo a gizmo has come to visit you guys wa I got him Gizmo say hi Oh no that's wicked wicked has come to say hi people yay everyone loves a wicket hi Wicket thank you for visiting hey buddy okay all right he's going off to bed I think awesome well we always enjoy visits from Wicket I thought it was Gizmo but Gizmo's in his bed right here parasites are considered pathogens because they can cause damage to host tissues and can sometimes even cause death to the host these parasites can range from viruses to worms so there are many different organisms and small infectious agents which are considered parasites an obligate parasite is unable to grow outside of the living host and an obligate intracellular parasite is a parasite that must spend at least part of its life inside of a host cell that's what intracellular means by the way inside of the cell so if it's an intracellular parasite this parasite lives and feeds inside of your cells whereas other parasites might live among your cells or on your tissues now most microorganisms especially single cell ones they lack a mouth right like you and I have a mouth and a digestive trct so how do these bacteria for instance how do they get their nutrition well it's called nutrient absorption the necessary nutrients must be taken into the cell and then waste materials must be transported out of the cell so this requires what's called transport things need to be transported into the cell and out of the cell through the cell membrane to understand how substances get into the cell or out of the cell through the plasma membrane we need to remember this concept of diffusion diffusion is a spontaneous process it does not require energy in fact diffusion releases energy diffusion is simply the movement of molecules in a gradient from an area of high density or concentration to an area of low density or concentration so if I for instance if I release a gas right here that gas will spontaneously diffuse through the room it will go from an area of high concentration where I release the gas to an area of low concentration you know the rest of the room and that's a spontaneous process it does not require any energy to occur if you remember from earlier biology classes this would be known as a spontaneous or negative Delta G reaction spontaneous reactions do not require energy and diffusion is an example of something that does not require energy it's a spontaneous process so for a substance to defuse across the cell membrane or plasma membrane this if it's happening by diffusion then it does not require energy next let's discuss osmosis osmosis is simply the diffusion of water across a membrane a selectively permeable membrane that's all osmosis means remember that a membrane is selectively or differentially permeable this means that not just anything can enter the cell and not just anything can float out of the cell the cell can determine what can enter the cell or what can exit the cell remember from earlier biology classes if you had them that when a membrane is placed between Solutions of different concentrations and the solute is larger than the pores then water will diffuse at a faster rate from the side that has more water to the side that has less water until equilibrium is reached so let me explain how osmosis Works osmosis is diffusion of water across a selectively permeable membrane so now let's take a look at this example from your book here we have solute and remember solute is the substance that's dissolved in the water and then you have the solvent which does the dissolving this is the water here you can see an example where we have a semi-permeable membrane outside in the environment we have pure water and inside of that membrane we have water plus the solute sugar Let's Pretend these dots represent sugar these red dots represent sugar if we take a close look at the membrane it is a selectively permeable membrane because it is permeable to water however it is not permeable to the sugar this means that the sugar cannot cross the membrane but the water can now let me ask you this and let me see if you can beat Wicket which way if the water is the only component that can move across the membrane not the solute which way will the water travel from the environment into the cell or from the cell into the environment let's see if you can beat Wicket that's right hopefully you got it correct just like Wicket and that means yes the water flows into the cell the water is more concentrated out in the environment the water is less concentrated in this cell and so the water will travel from where water is more concentrated to where water is less concentrated whatever is moving across the membrane whatever is whatever is diffusing Will diffuse from where it is high in concentration to where it is low in concentration if these pores were larger then the sugar the red dots would diffuse out of the cell they would go from in to out because the sugar is more concentrated inside than outside but remember the sugar cannot cross the membrane because the membrane is too uh the pores are too fine the membrane is selectively permeable and so the water is what's mainly crossing the membrane if that's true the water will move from where water is more concentrated to where water is less concentrated and yes if you're curious whichever way the solute would like to go whichever way the solute would like to diffuse the water always wants to diffuse the opposite direction so yes whichever way uh one wants to go the other one always wants to go the other direction remember just like this example here the cell itself has a number of solutes inside versus its environment sometimes the microorganism can find itself in an environment that has less solute concentration than inside and sometimes the organism can find itself in an environment with more solute concentration than inside and sometimes the organism is in an environment with the equal amount or equal concentration of solute inside and outside of the cell these are known as tonicity environments tonicity problems are osmosis problems it's water which is crossing the membrane into the cell out of the cell or having no net flow uh in or out of the cell I have a nice short video I would like you to watch I'm going to throw up a card uh here I'm going to throw up a card here and that will direct you to my review on tonicity and it's a thorough tonicity review I assume that most of you who have taken this class have also taken Biology 1406 where we talked deeply about tonicity and how the environment can affect a cell if not please go ahead head and watch that video so that you are brought up to speed and then meet me back here so that we can review how tonicity affects microorganisms I'll wait for you here in fact this might be a good break time with Gizmo and Wicket that way you could go watch that video and I can hang out with my cats all right we'll reconvene in just a minute [Music] welcome back from break time with Gizmo and Wicket let's get back into this review of uh tonicity problems hopefully my short review video helped you and you remember the concepts of diffusion osmosis dialysis you you understand isotonic hypotonic and hypertonic conditions that's great so let's do a quick review right here in an isotonic Solution that's this example on the left if we're dealing with a a type of cell wall lless cell this is a cell without a cell wall such as an amoeba or a parium in an isotonic environment expent there's equal concentration of solute inside of the cell as outside of the cell the solute is depicted here in green and the solvent is water you can't really see the water but you can imagine it's surrounded by water in this case remember for every one water molecule that enters the cell about one water molecule leaves the cell so there's no net flow of water in this case the cell will neither gain nor lose net water volume here this is a bacterial cell um remember bacterial cells typically have a cell wall here depicted in pink a cell wall of peptidoglycan and that cell wall is in addition to the plasma membrane is strengthening the cell in this case again there's a equal solute concentration outside as inside again it's a isotonic solution so water should not net flow into the cell nor should water net flow out of the cell we are at equilibrium either way the cells are intact the cells are healthy now let's discuss what happens in a hypotonic solution this means a solution with a lower solute concentration in the environment hypo means low hypotonic solution means a low solute solution in this case you have a lot more solute so you see the Green Dots here for instance I'll give you an example like salt let's say these Green Dots represent the solute salt and you see how there's a higher salt concentration inside of the cell versus outside of the cell this is known as a hypotonic environment in this case water remember solute cannot leave the cell solute cannot enter for the cell these are tonicity problems which means they are osmosis problems so only water can flow the solute can't leave the cell so water will enter the cell water will flow from where water is more concentrated outside of the cell to where water is less concentrated inside of the cell and if you don't have a cell wall to protect you from uh you know this this volume increase then that osmotic stress will lice the cell the cell will actually break apart and get destroyed Lis means to break the cell will lice however a bacterial cell in a hypotonic solution will fare differently because when water flows into the cell the cell will swell up however it won't pop do you know why it won't pop let's see if you can beat Wicket to the answer hey Wicket why does this cell not pop exactly right Wicket it's that tough cell wall that pep tiog glycan cell wall uh that cell wall is so firm that it prevents Lis of the bacterial cell same thing in Plants you know in plants plants can also withstand hypotonic Solutions or environments because plants have a cell wall of cellulose and that prevents them from exploding by the way you want to know a fun fact you know how penicillin works you know how penicillin is a potent antibiotic against certain bacteria well the way penicillin works is that it compromises the cell wall you see this cell wall in pink well that cell wall is compromised by penicillin penicillin prevents the cell from maintaining its cell wall and then guess what happens if if a bacterium can't maintain that cell wall of pepo glycan it's comp promised and then the cell will lice isn't that interesting so that's how penicillin works now our last example here a hyperonic solution remember this is an environment that has a high solute concentration compared to the cell so here you can see there's a lot more salt a lot more solute outside of the cell in the environment than inside in this case again the water will flow from where water is more concentrated inside of the cell to where water is less concentrated outside of the cell and that results in the cell shriveling up like a raisin and this is known as a shriveled uh cell or also known as a crenated cell now cells that have a cell wall they also shrivel but it's not the cell wall that shrivels notice how the cell wall did not change much it might be less bloated right the cell wall does not shrivel however the plasma membrane see here the plasma membrane in yellow the plasma membrane which should be pressed against the cell wall is now peeling away from the cell wall see how the plasma membrane has peeled away from the pink cell wall and so it's the plasma membrane that's that's shriveling up because of the water loss water is net diffusing out of the C this makes the plasma membrane peel away from the cell wall resulting in a what's known as a plasmalaser away due to efux of water in that hypertonic environment now recall that diffusion is a spontaneous process C diffusion occurs without energy input it is a negative Delta G reaction it's ex exergonic and so anytime you see the term diffusion you should you should think that no energy is required for that process to happen if a substance diffuses across the membrane itself this is known as simple diffusion and this is a type of transport because you're transporting a substance across the membrane and this is known as a type of passive transport passive meaning no energy is required so simple diffusion of a substance would be if a substance diffused across the membrane directly across a membrane and this is an example of passive transport because no energy was required to transport that substance into the cell so for instance if oxygen diffuses into a cell that's passive transport uh that's simple diffusion if CO2 diffuses out of a cell that's simple diffusion again a type of passive transport no transport protein is required for simple diffusion passive transport across a cell however if a molecule is polar or charged polar meaning it has partial negative ends or partial positive ends or charged as in ions like sodium cation or chloride anion in that case for it to diffuse and transport across the membrane it requires a transport protein so let's pretend that this molecule here here this molecule in purple let's pretend that's glucose or water which is a polar molecule or let's pretend it's sodium cation or chloride anion these substances cannot simply diffuse across a membrane because of the Polar uh the the nonpolar region here the these tails are nonpolar that means that polar and charged substances need to travel through Transporters to get into the cell because a transporter is required for this type of diffusion this type of transport that those proteins are facilitating the diffusion and this is known as facilitated diffusion facilitated diffusion facilitated diffusion unlike simple diffusion requires a transport protein to allow the polar or charged ion across the membrane again though it's a type of diffusion so that means no energy is required so it is also an example of passive transport now if you want to move a substance against the concentration gradient from low concentration to high across the membrane this is known as active transport and it's going to require energy energy is required energy is required for active trans transport moving a substance from low concentration to high that means you're going against diffusion and that would require energy that would not be spontaneous here we can see an example of active transport imagine if these Thumbtack looking things are some molecule and you're trying to expel that molecule where there's already a high concentration of these these molecules outside of the cell there's a lower concentration of these molecules inside of the cell and you're transporting these molecules out to where they're already high in concentration again this would be an example of active transport and it would not occur without ATP energy or some other form of energy in this case you can use that energy in order to move a substance against the concentration gradient that means against the for force of diffusion now this other concept of group translocation we're not going to delve too much into it but it simply means that when a substance is transported across the membrane by a facilitator by a transport protein it's modified along the way notice how these pink sub these pink substances they picked up a green square on the way in that means that the substance was modified upon transport across the membrane well that's what group translocation means and usually this modification is a phosphorilation like this this pink molecule picked up a phosphate group for instance but it could be other things as well now for the last type of transport that we're going to talk about this is uh another form of active transport but it's called bulk transport bulk transport because you are bringing bulky items into the cell or you are expelling bulky items out of the cell if you are bringing bulk into the cell this is known as endocytosis Endo meaning inside there are two forms of endocytosis and let's go over both in phagocytosis a solid a large bulky solid such as this bacterium for instance let's say this purple structure is a large bacterium the cell will the cell membrane will invaginate to form a vesicle around the food around the bacterium that's being phagocytosed and that vesicle will internalize it will pinch off it'll go pop it'll pinch off from the plasma membrane bringing in what's known as a food vacu all right and because you're bringing solids in in this manner it's called phagocytosis however on the right check out on the right um in this case the same concept is happening vesicles are forming bringing substances in but it's actually water that you are bringing in water is bringing brought in as VES in vesicles and because the liquid including anything that's dissolved in the liquid any any solute that's dissolved in the liquid is being internalized this is known as as pinocytosis and so the way you can remember this is Fage means to eat and and you when you eat you eat solids whereas Pino means to drink and when you drink you internalize liquids so both fagocitosis and pinocytosis are examples of endocytosis endocytosis is bulk transport bulk import of bulky material from outside and it's a type of active transport because it requires ATP energy or some other form of energy now let's move on from nutrients to environmental factors that can influence microbial growth here is a list of various environmental factors that can influence microbial growth we're going to start with temperature temperature is very important uh for microbes a microb survival is dependent on adapting to the habitat's temperature with regard to temperature each organism has a minimal temperature at which it can grow a maximum temperature at which it can grow and an Optimum temperature at which it prefers to grow below the minimum temperature that organism typically freezes it doesn't necessarily die it freezes above the maximum temperature usually the organism dies because its proteins and its other components of the cell they denature and they you know come apart and the optimum temperature this is the temperature at which the organism performs the best it grows the best at this temperature here and different organisms have different Cardinal temperatures so take a look here at ecological groups by temperature so take a look here there are some some organisms that prefer cold temperatures for growth in fact these organisms typically have an optimal growth temperature of around 4° C and with their minimal temperature being -20° C well below freezing and their op and their maximum temperature around 14° C these are known known as cyr files let me zoom in here for you cyr files cyr files prefer cold conditions for growth they grow optimally at around 4° C the same temperature as uh your refrigerator isn't that interesting so you would find these in colder habitats on the planet next we have these organisms here these organisms have an optimal temperature of around room temperature room temperature being between 24 25° C and with a minimum temperature of around 4° c and a maximum around 37° C these are known as cyr tolerant organisms next we have the green dash line here these are known as the mesophiles these grow best uh around around body temperature look around 37° C misop files prefer body temperature for growth and they have a minimal temperature around uh 10 11 12° c and a maximum around almost 50° C following that we have organisms that prefer very warm environments so for instance this pink line here these are thermopiles thermopiles prefer to grow in very hot conditions we're talking around 70° C this is hot enough to completely denature your proteins and kill your cells a mopile would die in these conditions and then we're not done yet there are some organisms that grow in even warmer environments look at this brown dash line over here these are known as the extreme thermophiles these organisms they can live in boiling hot conditions we're talking you know the sulfur cauldrons the Sulfur Springs that exist anywhere there are thermal vents where the water is so hot it's boiling these live in these boiling hot conditions and in fact they prefer to exist around 125° C environments you you will find these in thermal vents and such as I mentioned uh a lot of times these are archa you know many ARA are extreme thermopiles uh but also some bacteria are Extreme thermopiles as well now let me ask you a question let me test your understanding um look looking at these different um temperature types which of these five would you suspect would cause the most human diseases would be the culprit of the most human diseases and be known human pathogens or most likely to cause an infection in a human what do you think can you beat Wicked that's right that's right Wicked is always misiles well think about it misiles prefer 37 degrees for growth your body is at 37° so you know yes it's most of the human power pathogens are misiles why because those pathogens want to grow on your body because they prefer your body's temperature moving on to our next environmental condition for growth gases different microbes prefer different gases for growth atmospheric gases contain oxygen and CO2 you also have nitrogen in the atmosphere as well well some organisms can grow in the presence of oxygen and some organisms they cannot grow in the presence of oxygen there are three categories of organisms with respect to oxygen those organisms that can use oxygen and detoxify it those that neither use oxygen nor detoxify it those that do not use oxygen but can detox toxify it so let's delve into this concept of using oxygen and detoxifying oxygen and discuss what this all means well as it turns out oxygen can be quite toxic to the cell it can destroy cells but not in its normal form of oxygen gas O2 it's when take a look here as oxygen enters into cellular reactions such as metabolic reactions in a Cell it is transformed into several toxic oxygen products these are known as Ross or reactive oxygen species for instance singlet oxygen which is a single o a single oxygen is extremely reactive and it's produced by living and non-living processes this singlet oxygen if if it's present in your cells it can cause cell damage and cell death because it can cause oxidation of your cellular components again this buildup of singlet oxygen and the oxidation of membrane lipids and other molecules can damage or destroy the cell here's another reactive oxygen species it's called super oxide ion it's O2 with a negative charge here's another one hydrogen peroxide H2O2 and here's a third one hydroxy radical oh minus all three of these are examples of Ross reactive oxygen species which is created by cells during cellular reactions that can cause damage to the cell so much damage that it can kill the cell so when these when these Ross molecules build up in a Cell they need to be neutralized they need to be dealt with otherwise they could result in cell death so only those organisms that can neutralize these rusts can live in the presence of oxygen I hope that makes sense so for instance cells use enzymes that they code for in with their genes to scavenge and neutralize these Ross in a two-step process so for example step one the enzyme that's produced by a bacterium or microorganisms uh this enzyme superoxide dismutase will convert superoxide radical or super oxide ion to O2 minus it'll it'll convert that to hydrogen peroxide right hydrogen peroxide still a form of Ross it is a reactive oxygen species however the second enzyme again coded for by a microbial Gene uh the enzyme catalase will then take that hydrogen peroxide and convert it to harmless water so you see organisms that have these two enzymes superoxide dismutase as well as catalase they are capable of neutralizing dangerous Ross like this superoxide ion as well as hydrogen peroxide however an organism that does not possess super oxide dismutase nor cataly it will have a buildup of superoxide ion or even uh hydrogen peroxide and those reactive oxygen species would destroy the Cell Again by attacking the membranes Again by causing uh oxidation in the cell killing the cell so those organisms that can grow in the presence of oxygen need to create these enzymes or have these enzymes those that can't grow in the presence of oxygen tend tend to lack these enzymes so with regard to oxygen requirements aerobes or aerobic organisms are organisms that can use oxygen during metabolism these organisms do not get destroyed by reactive oxygen species this is because they produce the enzymes needed to process those oxygen products remember super oxide mutas and catalase in fact there are even organisms that are obligate aerobes an obligate aob is an organism that must grow in oxygen it cannot grow without oxygen there's another class of organisms called facultative Anor robes and these organisms they don't require oxygen for metabolism but they are capable of growth in the presence or absence of oxy o these organisms can grow in the presence or absence of oxygen the way they do that is they undergo aerobic respiration when oxygen is present and then they switch to fermentation when oxygen is absent another class are the micro aerop files these organisms they do grow in oxygen but only low levels of oxygen so they do not grow at normal atmospheric concentrations of oxygen the amount of oxygen in the atmosphere is between 20 and 22% and these organisms do not grow in that range they prefer lower concentrations of oxygen for instance 8 to 10% oxygen Anor robes or anob microorganisms these are organisms that grow in the absence of oxygen if it's a strict or obligate anoro this means that it lacks the metabolic enzymes uh necessary for processing oxygen so for instance because strict or obligate Anor robes do not produce the enzymes superoxide dismutase or catalase they are not capable of processing those reactive oxygen species like singlet oxygen or super oxide uh ion or hydrogen peroxide and that and then they succumb to those reactive oxygen so where you find Anor robes specifically strict or obligate Anor robes is you know places that have you know deep in the mud Lake ocean soil where there's very very little to no oxygen and the last class here are the arrow Pro tolerant Anor robes these do not utilize oxygen but they can grow to a limited extent in its presence and the reason they can withstand oxygen is because even though they don't use oxygen they have ways of breaking down peroxides and superoxide radicals and here we can see bacteria with different oxygen requirements growing in inside of broth here you can see if the bacteria only grows at the surface this is an example of a obligate arobe if it grew just below the surface just here but only just below the surface that would be a micro aerophile if it can grow in the presence or absence of oxygen then we're talking about a facultative anoro or an aerotolerant bacterium and if it only grows at the bottom of these tubes then it is a obligate anoro a strict anoro speaking of gases some microbes prefer high levels of CO2 these are called capnophiles capnophiles grow best at higher CO2 levels than normal atmosphere moving on to our next environmental condition pH parts of the Earth have different pH environments there are are acidic environments there are basic environments there are neutral environments and each of those environments has organisms that prefer to live in there remember remember that pH is expressed on a scale from 0 to 14 zero being very acidic 14 being very basic or alkaline ph7 refers to a neutral pH organisms that prefer acidic pH for growth are called acidophiles obligate acidophiles as the name suggests must grow in acidic conditions conversely alkalino files alkalophilic pH environments for growth moving on to our next environmental condition osmotic pressure these typically refer to hypertonic conditions environments with high solute concentration for instance high salt concentration in fact osmophile are organisms that prefer to live in habitats with high solute concentration halophiles as we've discussed before halophiles these are organisms that prefer High concentration of salt for growth obligate halophiles need high levels of salt for growth while facultative halophiles they can grow in the presence of high salt concentration but they do not need high salt to grow so for instance staf laus orius it grows on your skin and it's salt tolerant right it does not M that salty environment of the skin a nonh halophile would not be able to grow on the skin this is why skin infections are often caused by staff staf lakus orius staf laus epidermus these are bacterium that are Halo files facultative halophiles and they prefer to grow on the skin other bacteria may not be resistant to the Salt levels present on the skin and so this is why skin infections tend to be caused by staff or another salt tolerant microorganism the next environmental Factor radiation photot tropes use visible light visible light is a type of electromagnetic radiation but photot tropes use visible light radiation as an energy source and there are other forms of electromagnetic radiation that stream onto the earth from the sun as well as visible light these include ultraviolet or UV V light infrared light as well nonphotosynthetic microbes tend to be damaged or destroyed by radiation specifically UV radiation another type of radiation that can damage microbes is ionizing radiation x-rays or cosmic rays so some forms of radiation are required for life such as visible light radiation to photosynthetic organisms and some forms of radiation are delerious to life or damage life forms including ultraviolet or x-ray or cosmic rays as well moving on to another environmental Factor hydrostatic pressure deep in the ocean there is high pressure of water there's high water pressure and it's the barrel files that can live in this high water pressure deep sea environment moving on to the next environmental Factor moisture moisture is required for bacterial and microbial growth remember that most of a cell's contents is water most of the cell's mass is water so it's very difficult for microorganisms to grow in a waterfree environment and it's only those dormant dehydrated cell stages such as as spores or cysts that can tolerate extreme drying because their enzymes go inactive living organisms cannot tolerate extreme drying or desiccation now that we've covered the different environmental factors that can affect microbial growth let's discuss associations between organisms namely we're going to talk about symbi iotic associations we're not going to delve too much into nons symbiotic Rel uh relationships in this class symbiotic relationships are when organisms live in close nutritional relationships symbiotic relationships are when two different species coexist they live together however this can be beneficial or this can be harmful let me explain one type of symbiotic relationship is a mutualistic symbi biotic relationship this is the one that people think about when they think about symbiotic relationships this is when both members benefit both of the members are uh benefiting from one another this is a called a mutualistic symbiotic relationship however a commensal symbiotic relationship is when the commensal benefits the organism that lives on the host benefits but the other member is not harmed now during parasitism dur which is another type of symbiotic relationship parasites Depend and benefit from the host but the host becomes harmed the host is harmed the parasite benefits and again students don't usually associate parasitism with symbiosis but it is a form of symbiosis so we should know the three different forms of symbiosis now one type of Association I will talk about are biofilms biofilms are mixed communities communities refer to different species of different kinds of bacteria and other microbes all living together and helping each other out and here's how a bofilm works let me let me give you an example an example of biofilm would be the plaque on your teeth right the plaque that grows on your teeth that you need to brush off at the end of the day so here's how a plaque forms here's how a biofilm forms first pioneer bacteria colonize a surface so certain bacteria for instance they will adhere to the surface of your tooth enamel this would be your tooth enamel in the background and remember they use adhesion structures such as fim or slime layers or even fagula in order to stick to to the uh tooth surface at this point what's really cool is that these Pioneer organisms will secrete an extracellular material that helps keep them on the surface and serves as an attachment point for later colonizer they start secreting this goo and this goo is sugary proteinous goo and this goo allows other or organisms to also attach to this Matrix and at the same time as they're producing this gray goo they're producing these little red structures these are called Quorum sensing chemicals Quorum sensing chemicals are chemicals that are released by each of these microorganisms each of these bacterium release these Quorum sensing molecules and when a certain concentration of quorum molecules builds up that triggers a a an an a quorum sensing event in many but not all biofilms other species join and may contribute to the extracellular Matrix this sugary procious Matrix and or participate in Quorum sensing remember Quorum sensing refers to releasing these Quorum molecules once again once a threshold concentration of these Quorum molecules has built up these Quorum molecules will reenter these cells and Trigger more bofilm formation so let me explain making a biofilm making a bofilm makes no sense if you're all by yourself you know because it's expensive to secrete sugary proteinaceous Matrix you know this this Goo uh it's expensive for the cell to release this goo if there's one or two cells they may not want to expend the energy necessary to secrete this goo and so it's better to save your resources and not secrete the goo if there is no other bacterium around and how do you know if other bacterium are around that's where the Quorum sensing molecule comes in each bacteria releases this Quorum sensing molecule once the Quorum sensing molecule builds up to a high enough concent ation then it triggers the formation of the goo it triggers the formation of the extracellular Matrix this sugary protais Matrix which then allows other organisms to help colonize this bofilm and the biofilm matures a mature bofilm may stop or minimize Corum sensing um and then at that point other bacterium can go PL plantonic again and they could spread and go and start their another bofilm at this point as well and by the way where did Quorum sensing get its name do you know um in model Congress or in Congress anytime you have Congressional meetings with Congressional structure you have what's known as Quorum this means that a certain percent of the members need to be present in order to start the proceedings these are called Quorum molecules because they ensure that a that a significant number of satisfactory number of microbes are present in the environment in order to start the process in this case it's to create the extracellular Matrix this this kind of um sugary proteinaceous bofilm isn't that interesting again if you're all by yourself you're not going to reach that threshold concentration of uh Quorum molecule if you're if you're high enough density high enough population then you will have threat more than enough of this Quorum sensing molecule to trigger more biofilm formation so Quorum sensing is a way of bacterium realizing or sensing how many other bacterium are in the environment the reason for Quorum sensing is to make sure or ensure that costly cellular activities such as making a biofilm only occur when there are sufficient numbers of microbes in the environment isn't that NE a long time ago it was assumed that microbes had no way of communicating with one another until Quorum sensing was discovered so Quorum sensing again it occurs when a bacterium it makes more sense for them to do that cellular activity as a group than it would alone so for instance again making a bofilm it makes more sense to secrete that sugary proteinaceous Matrix that bofilm if you're in a large group and doesn't make sense to waste those resources if you're all by yourself another example making a toxin some bacterium they won't make a toxin uh against a a host unless there's again Quorum sensing and a sufficient number of bacterium in the environment another example did you know there are some bacterium that can glow like deep fish bacterium the bacterium that grow deep in the ocean where there is no light okay these bacterium can glow but only when they're in high concentrations in the pockets and the fish you know in different pockets and the fish membrane in the fish skin isn't that interesting so these organisms will not glow if they're all by themselves but they will glow due to Quorum sensing in a high population isn't that neat again bacterium use Quorum sensing in order to do cellular activities that Mak sense to do in good pop in high populations and not alone now for the last part of this chapter let's talk about population growth bacterial population growth bacteria grow not by mitosis but by a process known as binary fision which is much more straightforward and simple than than mitosis here's a bacterial cell you've got this stringy stuff which is the nucleoid right the single circularized chromosome the nucleoid here you have ribosomes as well those little dots um this is a young cell this cell will grow they will elongate you see how the cell elongates and the nucleoid is copied now you have two copies of that single circularized chromosome those two copies move to opposite ends of the cell and then a protein band forms at the center of the cell this is known as the fit Z band and then this Pro promotes uh cytokinesis remember cytokinesis the separation of the cell itself and the cyto Kinesis occurs uh by a process known as septum formation septum formation which is an inward growth of the cell wall of the bacterium when the the septum is complete the two bacterium are separated from one another however sometimes they can remain attached and this is how staf Arrangements can form or strepto Arrangements might form or Diplo Arrangements might form if they don't fully separate now let's discuss bacterial rate of population growth how fast do bacteria divide this is known as the gener eration time or doubling time of a bacterium it's the time required for a complete fion cycle this means one young bacterium growing elongating and ultimately becoming two identical copies right dividing into two cells hi Wicket Wicket has come to say hi he's on the table right now hi buddy Wicket wickets come to say hi hey Wicket it's always so fun having wickets come say hi hi buddy hi sweet buddy what are you up to oh gosh he's scratching he loves to scratch my monitor so that's what you're hearing right now we're taking a impromptu break time with Wicket wicked's here to say hi no he's very excited to visit hi buddy I love you hi buddy you hear him purring I wonder if you can hear him purring through the microphone let's listen really close love you buddy what are you up to Wiki one thing to keep in mind about the generation time is that with each new fion cycle each generation time this doubles the population of the bacterium so long as the environment remains favorable the D doubling effect can continue at a constant rate here we can see the cell division doubling time in the population if we start with a single bacterium the number of cells is one the number of generations is zero and to understand how many bacterium are present at this point we take two to the power of the number of generations in this case the number of generations is zero so we have 2 to the power of 0er organisms and that equals one there's one organism at Time Zero at generation Time Zero at generation time one uh by the way many bacterium divide between 25 minutes and 35 minutes so this is very fast for many bacterium they divide quite quickly so what let's say within 30 minutes the bacterium would double from from one bacterium to two right because that cell underwent uh binary fision at this point you have one generation one doubling and the number of cells would be two to the power of one or two total cells then 30 minutes later those two double so if both of those double now you have four cells this is your second generation to calculate the number of cells you take the base of two and to the exponent two because there have been two doublings and two to the^ of two is four and we can go on this way so this is known as a logarithmic growth scale with the base two these are the number of log base 2 doublings and because this is a logarithmic growth populations can explode in a short amount of time in fact for ecoli for instance it could take you know ecoli 25 to 30 minutes to divide if we start with a single ecoli it takes five hours or so give or take to make a a million ecoli so from one bacterium one ecoli it would take about 5 hours to make a million and I always ask myself I always ask my students let's see if you can beat Wicket if it takes one eoli five hours to result in a million ecoli right to divide and become a million population then how long would it take for another million for two million to form can you beat wicket all right wick it good job another 20 minutes so it took five hours to get your first million eoli but it would only take another 20 minutes to get your next million remember it's exponential growth every doubling time you are doubling the population so yes Wick it is right it would only take another 20 to 25 minutes to result in 2 million ecoli this is because the doubling time of eoli is roughly 25 minutes isn't that neat so this is why when we plate our cells on media you know if you make like a spread plate or a streak plate then you put those plates in the incubator and we come back remember two days later 3 4 days later you know and we take a look at those plates what do we see on those plates we see a bunch of bacterial growth and each one of those colonies represents Millions upon Millions upon millions of you know eoli or whatever species you're studying and the reason why you see those colonies is because a single cell divided exponentially right with a base of two they doubled every 20 25 30 35 minutes depending on the species and that resulted in a colony by the time you returned so a single cell became Millions upon Millions if not billions in a few short days this is also why we refrigerate our food for instance you know what happens when you take food out of the refrigerator any microbes that happen to be on that food start to divide right because they were not dividing so fast in the refrigerator but you remove that food from the refrigerator and those microorganisms start to divide and remember they divide exponentially so there might be just a few eoli on your you know potato salad when you removed it from the from the refrigerator but you left it on the counter well guess what after five hours on the counter each one of those ecoi is now a million right and if you leave it for another 20 minutes each one of those eoli is now 2 million and now if you were to eat that warm food that's been sitting out you know now you would get food poisoning you would come down with an illness right however if you had refrigerated that food uh then those bacterium would not have divided so fast your food would not have spoiled and you would have been fine eating that same potato salad if it had been properly refrigerated so now we know the importance of refrigerating our food right and it's all based on this chapter this chapter is so interesting it explains why we refrigerate our food why because many organisms that cause human diseases are these organisms that are misiles remember misiles grow best at human body temperature if we're keeping our food in the refrigerator at 4° C then that's below the minimum growth temperature of many misop files so those microorganisms can't grow and if they can't grow they don't form sufficient concentrations to cause human disease or food poisoning but if you remove the food from the refrigerator those microorganisms begin to animate they begin to grow and divide exponentially with logarithmic growth and next thing you know you have food poisoning so isn't that interesting also all the other environmental conditions uh play a role as well so for instance remember not all microorganisms can grow in high salt so this might be why we salt our foods to preserve them have you heard that salt is a preservative a very important preservative and by salting our Foods we can preserve them and prevent uh bacterial growth and and for the food to become spoiled well that's because not many bacterium are halophiles only halophiles can grow in high salt and so by doing that we reduce the number of microbes that grow on the food also dehydrating why does why does steak go bad so easily if it's left at room temperature but not beef jerky beef jerky turkey is just dried out steak so remember many organisms all organisms require moisture to grow and beef jerky is too dry to grow on right there's not enough moisture for the microbe to grow on that surface isn't that interesting also why do we pickle our Foods you know when you pickle a food it makes it more uh preserved it keeps its shelf life much higher you know pickles last a lot long longer than cucumbers don't they why is that well because it's an acidic pH it's an acidic environment and again only acidophiles would want to grow in that environment isn't that really neat how this chapter kind of plays into how we treat food and it should also play into how we treat um you know the clinic in the medical setting in order to help keep the health of our patients in order to prevent the spread of disease the better you understand microorganisms and their growth requirements as is the topic of this chapter the better you can treat for your patients but also the better you can stay healthy at home and with your own food you know in your own kitchen isn't that neat okay again if we plot bacterial growth on a log scale then it is a linear logarithmic growth of bacterium over time however if we do not use a log scale it appears like the bacterium grow asymptotically they grow exponentially but they form kind of this ASM toote uh as they grow so normally when we're talking about bacterial growth we depict it on a logarithmic scale so that you see this nice straight line here and for the last concept from this chapter let's talk about a population growth curve a growth curve is a predictable pattern of growth in a population of bacteria specifically let's look at a growth curve in bacterial culture this is also known as batch culture if you have let's say a limited environment with limited resources limited nutrients and limited space so for example what if I have nutrient like TSB broth inside of a test tube do you agree that there's limited nutrients in this broth limited space in this broth well that's what that's what bacterial culture means there's limited resources um so like imagine a flask of of broth or a test tube of broth well when we have a test tube of broth and we put some we seed it with some eoli we seed it with some bacteria there are one two three four very predictable growth curves that occur and this is how it works on the y axis we have the log scale of viable cells so we have the log scale of cells these are living cells and on the xaxis we have hours number of hours so when I place eoli this many be this many ecoli into broth at first there's always what's known as a lag phase during the lag phase this is a flat period on the graph when the population appears not to be growing this is because newly inoculated cells remember I said I just added some eoli to this environment I I recently inoculated the environment with eoli these require a period of adjustment enlargement and synthesis cells just can't multiply at their maximum rate so here during the lag phase the bacterium are becoming acclimated to their environment then at some point now that they're acclimated to their new environment they enter what's known as the exponential growth phase remember this is the log growth phase where the bacterium double and double and double and double every generation time every doubling time however at some point we enter the third phase of the bacterial growth culture growth curve phase uh here we see it's called the stationary phase at this point the part is kind of over we've exhausted all the nutrients and the space and the bacterium can no longer grow so at this point we enter stationary phase in which no doubling is occurring no bacterial doubling is occurring and then after a a period of time we enter our final phase the death phase because these bacterium have been stewing in their own way waste you know cuz there's waste in here there's no nutrients in here they become sick and a number of cells die off and this is known as the death phase sometimes known as the sence phase and that's it for this chapter we talked about uh all of the nutritional and growth requirements for bacterial cells and microbes I hope this chapter was informative it was really interesting reflecting back on how we treat our food and how it has everything to do with the bacterial nutritional and environmental growth requirements so I think that's neat I hope you found it neat as well um please let me know if you have any comments in the comment box below and I will catch you guys next time Dr D Dr D Dr D Dr D Dr D 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