today's lecture on is about prokaryotes and if we look at the word prokaryote uh literally meaning before nucleus for the fact that they do not have membrane bound nuclei not to be confused with eukaryotes uh which means literally means true nucleus as these are organisms that have membrane bound nuclei um let me just see if I can get a little bit of a marker that may be not as squeaky uh so prokaryotes uh again we're talking about organisms within the domain bacteria and uh if you uh remember from bio1 there are three domains of life you've got the domain bacteria the domain archea and the domain eukarya collectively the domain bacteria and the uh domain archea make up what we refer to as the prokaryotes and then of course domain eukarya are the eukaryotes and I suspect you may have done this in BIO one looking at the difference between prokaryotes and eukaryotes and again I'm not when it comes to size that sort of thing we're not going to ask you uh you know exact sizes but this is just to give you an idea as far as some of the characteristics prokaryotes small right everybody knows that typically .2 to 2 millimeters in diameter eukaryotes anywhere between 10 to 100 millimeters in diameter when we look at their nucleus we were already talking about this uh again in prokaryotes no nuclear membrane or uh nuclei but they do have a nucleoid a nucleoid region uh we're going to see that they have a single circular chromosome eukaryotes in fact do have a true nucleus consisting of nuclear membrane and nuclei membrane bound organ that's one of the big characteristics they do not have membrane bound organelle prokaryotes and obviously you talked about in bio1 the cytoplasmic organelle their present examples would be lysozomes golgi apparatus endoplasmic reticulum mitochondria and chloroplast are all examples of membrane uh enclosed organelle flagellum uh as far as prokaryotes consist of two protein building blocks and what's interesting about them is they are characterized by having a rotary or propeller like motion so rotary motion and like I said like a propeller rotary motion in the case of eukaryotes they're actually uh the flagellum is quite complex consisting of multiple microtubules and uh you might describe their movement wavelike or undulatory motion like the sperm cell glycocalyx and again this typically surrounds the uh cell wall uh and it can be a sticky substance it can be protective in nature can be consisting of of carbohydrates and protein it's usually present as a capsule or slime layer in prokaryotes and one of the big functions is uh protection eukaryotes uh it's present in some cells that do lack a cell wall the glycocalyx moving right along as far as the cell wall is concerned in prokaryotes usually present chemically complex typical cell wall includes a a polymer that we're going to see later called peptidoglycan which is kind of a mesh meshlike in nature and it's usually consists of proteins and sugars uh when present chemically simple and if you think about it we've got plant cells have got cell walls right the main constituent is cellulose uh fungal cells fungi have cell walls and it's made up of an insoluble polysaccharide called chitin not pronounced chitin uh as far as uh the plasma membrane you perhaps know it better as the cell membrane uh no carbohydrates and generally lack sterols like we see obviously in eukaryotic cells sterols and carbohydrates that serve as uh receptors and uh when they're present and as far as cytoplasm and again you may have had this in bio1 uh let me Erase here uh notice cytoskeleton or cytoplasmic streaming uh that we refer to as cyclosis if you look at a eukaryotic cell like a plant cell perhaps you did this in bio1 you can actually see cytoplasmic streaming under the microscope and again we refer to that as cyclosis but there is no cyclosis or cytoplasmic streaming obviously in uh in prokaryotic cells eukaryotic cells you do have a a cytoskeleton and you do have cytoplasmic streaming or what we refer to as uh cyclosis the uh chromosome as we said previously a single circular chromosome characterizes prokaryotic cells single circular chromosome lack histones uh proteins that are typically associated with chromosomes and again if we look at eukaryotic cells multiple linear chromosomes with histones cell division binary fision which is characteristic of prokaryotes and again we typically have mitosis that we associate with eukaryotic cells in binary fision uh there you might put down no it's like mitosis but there are no mitotic phases and there's no spindle apparatus no spindle or no spindle apparatus as far as sexual reproduction no meiosis uh transfer of DNA fragments only conjugation again we'll talk about lateral gene transfer and again in eukaryotes it involves meiosis this is a nice picture diagram out of your textbook and we want you to know some of the general characteristics of bacterial cells here are these small hairlike appendages we call fimbriae obviously responsible for having bacterial cells adhere to one another and adhere to the substrate here's that capsule that sticky capsule we were talking about the glycocalyx sticky layer of polysaccharide or protein that again help in cell adherence and also may be involved in evasion of the host immune system as far as internal Organization no nucleus and other membrane bound organelles and we don't have uh the complex compartmentalization here's the flagella that is so characteristic of prokaryotes and again structure is going to be different than eukaryotic cells and again the rotary motion that is so typical of prokaryotic cells you also have an appendage that's called a sex pillis that facilitates conjugation and we will see that in a little while here's your single circular a chromosome and accompanied by smaller rings of DNA called plasmids and as we will see plasmids are are involved in uh antibiotic resistance and the cell wall and notice it says found in nearly all prokaryotes and we're going to see structure differs in gram positive and and gram negative nearly all prokryotes there's a group that are called mycoplasmas uh we talk about mycoplasma pneumoniae causitive agent of walking pneumonia or some probably better called atypical I think it's sometimes called atypical pneumonia you know people say they've got a a chest cold and that's kind of a lowgrade form of pneumonia but that's an interesting pathogen because that is not characterized by having uh a cell wall so that's an interesting aspect of the mycoplasmas reproduction and adaptation Prokaryotes can reproduce quickly by binary fision and we talked about that some actually form endospores and these are dormant cells that can remain viable for centuries until the environment becomes suitable enough that they can literally become viable so it's a kind of a one of the classic examples is anthrax which has been used in unfortunately bioterrorism because again they can lay around for years and years and years and and then become viable so it's kind of an adaptive cells prokaryotic populations can evolve in short periods of time in response to changing environments we said that mutations are rare and random in large organisms but in prokaryotes they are way of life that's a typical way that they evolve is obviously through mutations and that sort of thing so they wrote the book on natural selection rapid reproduction mutation and genetic recombination promote genetic diversity and this is extremely fascinating and again we talked about earlier the fact that many of these pathogens have evolved antibiotic resistance and in that way are truly a challenge to deal with because prokaryotes often proliferate rapidly mutations can quickly increase a population's genetic variation enabling adaptive Evolution and again we're talking about things like anti-biotic resistance genetic recombination talk about genetic diversity and that can actually arise from what we refer to as a lateral gene Gene transfer sometimes called conjugation and I think we can show you what we uh mean here by bringing this up and again we've talked about the sex pillis and here is the sex pillis so here is our donor bacterial cell with a plasmid and as I said before these are accessory genes that are involved in antibiotic resistance and they obviously divide independent of the main chromosomal DNA and here we've got the recipient and again with your single circular chromosome and here we've got the sex pillis engaging both the donor and the recipient and notice the synthesis here of a plasmid they disengage this is now the old donor and this is now going to be the new donor and you notice we have synthesized a plasmid which might be involved obviously in antibiotic resistance so all of this can occur very very rapidly by what we refer to as conjugation or lateral Gene transfer this is actually quite a fascinating thing talking about nutrition and metabolic adaptations in prokaryotes and we're going to see of all the life forms on the planet it is the prokaryotes that show the greatest diversity in modes of nutrition they can be photo autotrophic they can be chemo autotrophic they can be photoheterotrophic and they can be chemoheterotrophic so let's break this down a photo- meaning light right -autotrophy literally meaning self-feeding right you should know what autotrophic and heterotrophic is from bio1 chemo autotrophy you're making your own food with chemicals right photoheterotrophy in the presence of light you are a obtaining nutrition by an outside source and again chemo trophy obviously a outside source and you are taking in the case of humans organic chemicals which we refer to as food so let's take a look at this okay so as I was saying previously here are the major nutritional modes we break down obviously the mode of nutrition energy source carbon source and types of organisms examples and on an exam I can clearly ask you what's the energy source what's the carbon source and can you give me some examples so the first and again the two big breakdowns autotroph heterotroph self feeding right self- nutrition or different food different nutrition you're not making your own food under autotroph you can be a photoautotroph you obviously can make your own food in the presence of light light is the energy source or you can make your own food and your energy source are inorganic chemicals so this is how we break it down so the first one photoautotroph what's your energy source light what's your carbon source atmospheric carbon dioxide or if you're in water it could be bicarbonate ion or some related compound examples photosynthetic prokaryotes in other words cyanobacteria and we will talk about the cyanobacteria which might be something like as we'll see later something like the genus nostoc or oscillatoria these would be and again it's a Genus so we underline or we italicize these would be examples of photosynthetic prokaryotes plants obviously photosynthesizers certain protists again example would be some algae that sort of thing right so and again on this the the big one that everybody knows are plants plants are photosynthetic right but again we're talking prokaryotes chemoautotrophic again what's your energy source um inorganic chemicals it can be hydrogen sulfide which smells like rotten eggs it can be ammonia or it can be iron ions what's your carbon source again car carbon dioxide atmospheric carbon dioxide bicarbonate or some related compounds and again this is kind of unique to certain prokaryotes if we go to hydrothermal vents under the ocean many of you know that these are very very hot areas where we find some interesting life forms under the ocean or volcanic areas and places like Yellowstone where there are geysers and that sort of thing you can get these these chemoautotrophs right I will hold you to the genus sulfolobus and again we typically find these existing in very hot volcanic areas sometimes and this would be a great example of what we refer to as an extremophile lover of extreme and in this case it would be a thermopile as we find them in what very very hot environments they belong to the domain archea and the archean can be bacterial types that live in extreme environments but we also see that they can also live in Fairly moderate environments the ones that people love to talk about are some of the ones that live in volcanic areas very hot environments but we will see later that archea can live in fairly moderate environments so under autotrophy you can be a photoautotroph or a chemoautotroph under the next big category heterotroph you can be a photoheterotroph and again we can ask you what is your what is your energy source what is your carbon source so here photoheterotroph your uh energy source is going to be light, "-photo", and then obviously your energy source uh organic compounds right so again you need to certain uh Aquatic and loving prokaryotes halophile literally meaning lover of salts so halophiles we would see in places like the Great Salt Lake in Utah uh the Dead Sea in the Middle East would be another situation uh where we would find uh some of these salt loving prokaryotes okay and again we will hold you to the genus rhodobactor as an example again it's a Genus because it's italicized and then chloroflexus would be another example of what we refer to as a photo heterotroph and the last one here is what we refer to as a chemoheterotroph let me Erase here a little bit and again we've got a situation where we've got again organic compounds and uh organic compounds here okay like we saw your energy source here was light your energy source obviously here is organic compounds okay many prokaryotes most of your prokaryotes are going to be chemoheterotrophs and again the example clostridium which we will see later uh and protists uh these are unicellular although there are exceptions it's quotes when we get to protists you'll see why it's not a term that I really like much but uh unicellular eukaryotes fungi animals obviously including humans uh so here we go with obviously uh we take in food which is you know organic compounds and obviously representing organic compounds as well and then some plants so the question is on the plants what's going on here yes they are photoautotrophs but some plants some of you may have been already thinking about um uh carnivorous plants ie Venus fly traps so the story on these guys is basically they're photoautotrophs right but think of trapping these insects as like little packets of fertilizer plants can live without fertilizer but if you give it to them they they do better not to elaborate too much but these plants are typically found in swampy or boggy areas where you have very little nitrogen and phosphorus so in order to supplement some of this they will trap insects okay so that's where we get chemoheterotrophs yes they're basically photoautotrophic but they can supplement obviously with uh insects