okay today we're going to talk about chapter 27 bacteria and archaea this is a really exciting chapter that covers a lot of varying information but we're going to try and go through it all um Okay so bacteria and Archaea are both prokaryotes carrots you remember what that word means um which are technically the most abundant organisms on Earth pretty impressive um it has been said by scientists that the number of prokaryotes in one handful handful of fertile soil is greater than the number of people who have ever lived on Earth period not the number who are alive currently but who have ever lived which is pretty impressive I don't think we have a very good understanding of how how many that is right um they are all single-celled organisms prokaryotes are all bacteria and Archaea and they make up two different domains the domains of bacteria and archaea which I want you to know if you don't remember what a prokaryote is from a previous biology class please go back and review in chapter 26 I mean I'm sorry chapter six um so prokaryote as compared to a eukaryote we as humans are eukaryotes as mammals it's animals um eukaryotic cells you go back to chapter six have a nucleus and membrane-bound organelles that's what we have prokaryotic cells do not have a nucleus or membrane-bound organelles it's kind of the main difference so there's a lot of other ones as well those are the big ones so in life we know of three domains humans have classified life into three different domains that's the biggest broadest category if you remember that from the previous chapter so the domain bacteria the domain Archaea and the domain Eukarya so technically we are in um this domain of Eukarya and all animals are in this domain of eukaryote and I know this is animal biology but today just for one day we're going to talk about the other two domains and we're going to classify all of this into we're going to cram all of this into one chapter okay so one chapter on things other than animals but I think you'll see that they definitely highly affect animals so it's important to cover still in the concept of animal biology okay um so again prokaryotes we're referring to both bacteria and archaea when I use that word prokaryote okay so there's some things that we need to talk about um uh specific characteristics about prokaryote prokaryotes that enabled them to reach giant population sizes and Thrive really thrive in very diverse and sometimes very hostile environments it's actually pretty impressive and I hope by the end of this lecture that you will have a newfound respect for bacteria and archaea for prokaryotes so one um prokaryotes are tiny and I know that we know they're all microscopic I think there may be a couple that are not microscopic but they're still very very very very small um and in comparison to the size of even one eukaryotic cell so we're talking about single-celled organisms their entire organism is one little bitty cell even when you compare prokaryotic cell to a eukaryotic cell eukaryotic cells are much bigger okay so these are teeny teeny teeny tiny microscopic organisms um and because they're so small and because of how they reproduce they can reproduce very quickly they reproduce the Via binary fission it's asexual um and their populations can reach enormous numbers can which really changes um and is different from how most eukaryotes eukaryotes excuse me interact with your environment they're not usually able to reproduce quite this quickly okay um also so because prokaryotic populations are so large mutations um Can Happen more not because the rates of mutation are higher but because their populations are so large and they're reproducing so quickly so that enables a high genetic diversity which allows for Rapid Evolution we're going to talk about that more detail um their diverse adaptations allow prokaryotes to live in a wide range of environments including this really hostile crazy hot spring this is in Yellowstone National Park prokaryotes live here in this really hostile environment so we're going to talk in more detail about that as well um and Rapid Evolution and prokaryotic populations results in a diverse metabolic and structural adaptations including this endospore so we're going to talk about this in more detail here okay so again I want you to remember this prokaryotes are all unicellular which means single celled in comparison to eukaryotes which can be single-celled and we're going to see that next chapter but they um can also be multicellular okay they are teeny teeny tiny much smaller than eukaryotes even single celled eukaryotes the biggest one um is supposedly supposedly the size of a puppy seed if you know how big a puppy you see this I plant poppies they're pretty teeny teeny tiny but they can be seen they can come in a variety of shapes the spherical shape right here these are all in your textbook which is called cocci Rod shape which is called bacilli and the spiral shape which is from those spiral Keith which are kind of I think the funkiest looking um and the cell you know the one celled organism is actually very well organized so it's pretty impressive that in this one single cell um this prokaryote can achieve all of its life functions everything that needs to happen in that one little bitty organism happens in one cell right which is actually I want you to kind of acknowledge how impressive that is for us who have you know so many different organs that help us survive okay so the cell wall and prokaryotes um what does that do we don't have cell walls right as mammals but other organisms do have cell walls like plants and fungi um in prokaryotes they all have cell walls what that cell wall does is it maintains the cell shape and protects the cell another thing it does is it prevents it from bursting in a hypotonic environment if you don't remember that word or how cells interact with their environment in that way please review chapter seven so what that means is that hypotonic means it's the environment is less salty than the inside of the cell and therefore it encourages water to move into the cell but if an animal organism excuse me has a cell wall it'll uh help prevent it from bursting from taking in too much water and this also has to do with why we use salt for preserving food so I have a picture sure here of some lemons that I preserved from uh I got these in South Texas and I preserved them using salt they're delicious actually um so in a hypertonic again review chapter seven if you don't know what I'm talking about that means that the external environment to the cell or the organism is more salty than the inside of the cell so it causes water to move out of the cell instead of into the cell so it water moves to the Salt to your environment and in that case prokaryotes lose water and they cannot reproduce very rapidly so salt has been used historically as a preservative um okay so when we're talking about a cell wall and prokaryotes um and we're classifying right bacteria and Archaea are both prokaryotes there's something that's a very big difference between these two domains and what their cell walls are made up of so peptidoglycan which is a word that sounds really long and scary but I want you to know this word peptidoglycan is a polymer composed of modified sugars cross-linked by short polypeptides basically it's something we're going to talk in more detail throughout this lecture but it can be found in the cell walls of most though not all bacteria species peptidoglycan and there's a lab that will help you kind of break this up a little bit more and learn a little bit more about this and in archaea no species of archaea have peptidoglycan in their cell walls they still have a cell wall but it's made up of different things okay um when we're talking about bacteria in particular so let's leave our key off to the side for a little bit there are two main types um again they describe most bacteria species they're not all there's a few outliers the two main types of cell walls we're going to call a gram positive bacteria and these have a very thick outer layer of peptidoglycan it's actually a simple simpler cell wall structurally but it has a thick layer of peptidoglycan gram negative bacteria so there's two main types of bacteria species have less peptidoglycan in their cell wall there's still some but it's not quite as much and gram-negative bacteria have a structurally more complex cell wall they have an outer membrane that contains lipopolysaccharides so it makes them a little bit more difficult to treat if you have a disease caused by that so here's a diagram from your book gram-positive bacteria have this very thick layer here of peptidoglycan that is all peptidoglycan so this will be the inside of the cell right here this will be the outside of the cells you can see inside outside so the plasma membrane is the inner layer and the outer layer has this really thick layer of peptidoglycan this is gram positive with the thick layer gram negative bacteria um again so this is the this is the layer this is the inside of the cell this is the outside of the cell um there's this plasma membrane and then there is peptidoglycan in here but it's a much thinner layer and it's like sandwiched in between these two um two membranes right and this outer membrane on gram-negative bacteria is much more complicated and it has something called lipopolysaccharides in them so you're going to do a lab this week on gram positive and gram negative bacteria you're going to learn how to stain for them why they're called gram-positive grain negative bacteria so I'm not going to dive into a lot of details about that but I want you to make sure you understand that in your lab because it may include that in a test okay okay so why do we do something like gram staining why does it matter if they have gram-positive gram-negative bacteria right it actually is a valuable tool in medicine today and in how we treat certain diseases so um if the doctor was treating a patient that came in say like the emergency room and was really really sick and they thought they had a bacterial infection they could very quickly determine if that patient's infection was due to a gram-positive or a gram negative bacteria and that might change how the doctor would treat that infection because gram-negative bacteria again that's the one that has the more structurally complex cell wall with less peptidoglycan those bacteria tend to be more resistant to antibiotics okay because of their that outer layer on the cell wall and that helps also protect that type of bacteria that species of bacteria from the body's defenses so a lot of times these are harder to treat gram-negative bacteria but that make it make a big difference in which antibiotic the doctor decides to give to the patient or what other techniques they might try to treat the patient so um you'll hear that talked about in the medical world quite a bit um so antibiotics in general let's talk about how some of them work many of them work when we're talking about um treating bacteria so please remember in this class I really want you to learn that antibiotics treat bacteria and when we're talking about diseases and prokaryotes and stuff we don't know of any archaea that cause diseases in humans so the prokaryotes that cause diseases are bacteria and antibiotics treat bacteria antibiotics do not treat viruses right so viruses are a totally different thing they're technically classified as non-living whereas bacteria are definitely living and antibiotics do not work at all on viruses okay so we're talking about diseases that are treated by antibiotics we're only referring to bacteria and many antibiotics work by attacking specifically that peptidoglycan in the cell wall which is kind of interesting so the way that those particular antibiotics work is to cause that cell wall to become unfunctional for whatever reason however that antibiotic works and the cool thing about that is that those type of antibiotics don't harm human cells at all because human cells humans are eukaryotes um don't have cell walls and we don't also don't have peptidoglycan okay so those antibiotics that are specifically targeting peptoglycan are only targeting bacteria species um so they work well for humans um so in addition to the cell wall that can that does have peptidoglycan right um many prokaryotes have an extra layer outside of that which is kind of crazy um this word it's referred to as a capsule if that extra layer is very dense and well defined you can kind of think of it as the capsule of a pill right so something that's well defined relatively thick if it's not densible defined it's called a slime layer ooh gooey that sounds kind of gross okay but um a capsule is also sticky which is different from if you were to picture like a pill a medicine or something um and these sticky outer layers help the prokaryotes stick both to each other and to their substrate whatever it is they're sticking on so right here um in this picture where's my mouse so this is the cell right here this cell wall is in um yellow right here and then this capsule right so see how thick that is it's thicker than the actual cell wall it's green in this picture and it doesn't look like super super like uh hard on the outside it does look sticky right and this um particular bacteria um stretch streptococcus which I believe is the bacteria that causes strep throat is attaching to a tonsil cell and a human right so that's its substrate the tonsil cell and that capsule helps it attach like that okay so this is something outside of the cell wall okay the other crazy thing that bacteria can do and this kind of blows my mind is that they can form an endospore and those are resistant cells that can develop to withstand extremely harsh conditions in the environment of the bacteria okay so what happens is they basically that cell squirts out excretes all the water essential nutrients metabolism completely stops the outer layer the outer the original cell um lysis which means it breaks open and then releases this endospore so in this picture right here this is the original bacterium right here so this is the organism the one cell and then this is the Indus score so basically primarily has DNA whatever else that needs to to survive long term and then it makes this really thick coat right here and then this outer layer breaks open um then this endospore here can survive pretty extreme conditions depending on what species you're talking about most endospores can survive boiling water right and Other Extreme conditions and the nutso thing to me is that some of these many of these endospores so they're not it's like they're living but they're not living I worked with fairy shrimp so it kind of reminds me you know of the eggs that they lay there but um oops excuse me but this endospore it's not reproducing it's not going through metabolism or anything it's existing and it can do that remaining dormant for like multiple hundreds of years centuries and then when the environment gets right again it can then become um alive not that it's dead as an in this world but then it actually interacts with the environment it starts metabolism up it can reproduce that sort of thing so um pretty crazy thing pretty cool thing that the bacteria are capable of is forming this endospore so I want you to know what that word means right what that refers to um let's talk about the external features of prokaryotes and you may have learned about this before I hope you have but just as a review and I want to make sure you do know this now a flagella singular flagellum um it's what you kind of think of as the tail but you um you know an organism a prokaryote can have multiple flagella they can be concentrated at one or both ends or they can be scattered all over the surface of the cell pillai which are right here in this little um picture here um those are technically the appendages that pull two cells together before DNA transfer from one cell to the other we're going to learn about how um prokaryotes have this an amazing ability to actually send DNA from one cell one organism to another despite the fact that they reproduce asexually okay it's just kind of crazy and then fimbriae are hair-like appendages that help stick you know help that prokaryote stick to another prokaryote or to a substrate so flagella pillai and fimbriere I want you to know the difference between all of those and what those are this is a picture of fimbriere so it's kind of these orange things all over it definitely looks sticky doesn't it um here's a picture I thought of a flagella that I thought looked kind of cool right here so this thing has what I would call you know to me that looks like three Tails but that would be called three flagella your textbook goes into a lot more detail about the mechanism behind um the flagellum and how they work and the motor and all that kind of stuff I'm not going to have you learn that for this class you could definitely read it but I'm not going to test you over that level um there but I do want you to know what that is okay um so let's talk about how the DNA is organized in prokaryotes so back to chapter six again the difference between eukaryotes and prokaryotes is that prokaryotes have no nucleus which is where the DNA is stored in the eukaryotes and they also have no membrane enclosed organelles like what we have mitochondria that sort of thing however they do have something known as a nucleoid which is a region of the cytoplasm the cytoplasm is like the jellian inside of the cell if you ever made a cell diagram or something like that where the DNA is located it's not actually enclosed by a membrane but all the DNA kind of hangs out together clumps up in that area and that's known as nucleoid prokaryotes also have they only have one chromosome and it's round one round chromosome versus eukaryotes and humans we have linear chromosomes and multiple linear chromosomes we don't have round chromosomes in the nucleus of our cells so nucleoid something I want you to know and that prokaryotes have one round chromosome in addition they have something known as plasmids which are smaller rings of independently replicated DNA much smaller most only carry a few genes so you should be doing a lab and lobster that will kind of better uh draw this out for you but I want you to know all these terms okay so nuclei nucleoid one round chromosome but they also may have multiple plasmids get smaller Rings independently replicating DNA so here's a diagram of a prokaryote you can see right here this is its one round chromosome and the nucleoid region here okay so um when we're talking about ribosomes again I hope you'll remember what these things are and if you do not please go back and review that early on in the textbook even if you bought this textbook only for this class you have access to all the earlier chapters so go do that so um ribosomes are located in both eukaryote and prokaryote cells okay ribosomes are technically not membrane-bound organelles um but um the ribosomes are are functions are not they're not functionally different they they are physically a little bit different and prokaryotic cells than they are in eukaryotic cells the ribosomes and a prokaryotic cell are slightly smaller than those in a eukaryotic cell so they're referred to as 70s and a prokaryote an ads and a eukaryote they also differ slightly in their protein and RNA content basically what makes them up they function the same they're just built a little bit differently um so along these same lines there are certain types of antibiotics again which we use to kill bacteria that can and do bind to ribosomes and prokaryotes because their makeup is a little bit different but they do not bind to the ribosomes and eukaryotes so that makes it safe for humans to take this antibiotic it only attacks bacteria it's another kind of interesting note there um okay so how do prokaryotes reproduce they do not reproduce sexually like we were talking about in the previous chapter we spent a fair amount of time talking about that they reproduce asexually okay so they reproduce by something called binary fission which the cell basically splits in two and again because these are single-celled teeny tiny organisms that don't have a lot of complexity you know there's not all of this membrane-bound organelles and that sort of thing they can reproduce and split into pretty pretty easily sometimes pretty quickly which would which could be shocking to us so many prokaryotes can divide every one to three hours and some can divide in 20 minutes which is very very quickly imagine if you know an animal that you knew of some mammal could reproduce every 20 20 minutes that'd be pretty shocking um so let's talk about those species that could divide in 20 minutes if an organism a prokaryote did that so you started with one prokaryote and again when it's replicating asexually via binary fission it's Offspring or an exact DNA replicate of itself right they're not different from the parent they're the exact same copy of the parent one prokaryote doing that could give rise to a colony in two days that outweighs planet Earth okay that's shocking but obviously that's not actually happening right now right because otherwise planet Earth would just be weighed down with all of these prokaryotes um prokaryotes are limited by many things just like other organisms are we're going to talk about ecology at the end of the class and really get into that a lot more but they're limited by food by Resources by nutrients by competition with other species by predation by hostile environments you know that sort of thing but it is possible for them to reproduce that quickly and so because of that prokaryotic populations can be significantly larger than populations of plants or animals that we can see with our eyes so there could be potentially trillions of individuals of one species one population which rarely happens with any species of plant or animals so there's a lot of organisms in one population so along those lines mutation and prokaryotes the rates of those and if you don't remember what a mutation is again please go back and review that I don't remember off the top of my head but there's a lot of genetic chapters in this textbook that cover mutations so in a prokaryote the rate of a one mutation happening is actually pretty low so it's 1 in 10 million in one gene one in 10 million that's a pretty low rate right but if you count for the fact like how fast prokaryotes are reproducing and then how many individuals there are in one population technically if you're talking about E coli in the gut of one human right you could technically get eight billion new mutations in one population of E coli and one human's gut in one day that's crazy because there's this many which I think is 20 trillion is that what that number is um new E coli that are actually made per day via binary fission in one person's intestines so think about that for a second so continuing kind of in summary of that idea though mutations in prokaryotes are rare on a per Gene basis they can really increase genetic diversity that's how that's one of the sources of genetic diversity if you remember that back from the last exam one of the sources of genetic diversity is mutation so these mutations can increase the genetic diversity quickly when you're talking about species prokaryotic species with short generation times and very large populations that can eventually I mean more quickly actually lead to lead to change in that population so again we're going back to the ideas of natural selection right so prokaryotic individuals that survive better in an environment will then go on to reproduce more and they will pass on those characteristics and then you know that'll end up changing the population and when we're talking about these teeny tiny rapidly reproducing organisms that can happen a lot faster than you would think so when we're talking about prokaryotes I feel like they get a bad rap a lot of the time we see them negatively everybody hates bacteria not that there aren't really horrible diseases caused by bacteria um but these organisms bacteria and Archaea are not primitive or inferior organisms they are simpler and the structure to their cells but it's shocking and pretty um I don't know I feel like they deserve some respect in how they can adapt so rapidly to new environmental conditions and go on to survive so you could potentially call them successful right again not that we as humans want all of them to be successful because some of them cause harm to ourselves but I always wanted to put some really cool pictures here that I got at the internet to kind of look at the cool structures these are really impressive organisms okay um and I'm going to stop right here and we're going to go on and continue in the next part of the lecture okay so this is part one I'll see you in part two