Bacteria Structure and Function | Microbiology Lecture

[00:00:07]what's up ninja nerds in this video we're going to be talking about the structure and function of bacteria before we get started if you guys like this video you benefit from it please hit that like button comment down in the comment section and please subscribe also if you want some awesome illustrations and notes to follow along with this video check that down in the description box below alright ninja nerds let's get into it all right engineers when we talk about the structure and function of bacteria we should have a basic understanding of just a little bit about the structure so if we take this nice beautiful little diagram here uh of a bacteria we should kind of point out some of the different components of it we're going to go into a little bit more detail on those structures a little bit more about what they're made up of what they do what's the significance of it but let's just have a basic idea of the basic anatomy or structure of this bacteria so first thing is let's talk about some of the things that are coming off of the bacteria which we're going to refer to as appendages some of these things that you guys want to know is first one is this big old orange thing that's popping out off this thing what is this structure here called do you guys know this is called the flagella okay so this structure right here is called your flagella and obviously we'll talk about what that does and what it's made up of in just a second these little brown things the tiny little brown things that are coming off of this actual bacteria here these little guys here are called your fimbre and then this big one here this longer one which there's less frequent of is called your pilous so these are some of the big appendages that i want you guys to remember big orange thing flagella little guys with numerous amounts of them is fembre and this long one which is usually less frequent a little bit longer is your pileus okay now the next thing that i want you guys to know we're not going to actually have it visualized inside of this bacteria but some bacteria we'll talk about in a second can have these structures inside of them called endospores we'll talk about that a little bit later though all right the next thing is basically the actual kind of like cell envelope okay this bacteria has this big thick kind of like blue wall around it and that big thick blue wall that we're going to discuss in pretty good detail later is made up of multiple different components and that's called the cell envelope and again we'll kind of dig into that talk about the multiple layers of the cell envelope what they're made up of what's their function okay so so far we have the appendages we'll talk about a specialized structure called the endospore which isn't pictured here then we have the covering around the actual bacteria which is this big thick kind of blue wall called the cell envelope made up of multiple different layers inside of the bacteria though you'll actually notice a couple different things you have all these like little sorry not blue red dots these red dots are all of your ribosomes so you have a bunch of different ribosomes baby little ribosomes present inside of the actual bacteria and then you have a big kind of purple entanglement of dna this right here is actually called the bacterial chromosome okay so this is your bacterial chromosome okay so we're just going to call this the bacterial chromosome and then this little guy right here is another piece of dna actually present in the bacteria but it's not a part of the bacterial chromosome and only actually some bacteria have this and it's a little circular small piece of dna and this is called your plasmid and again we'll discuss this a little bit later as well but these are some of like the basic things that i want you guys to know about the actual bacterial structure again real quick recap appendages give the flagella which is this orange structure little guys coming off of the fembre the long ones which are usually less a number of them is the pilus you have this big blue kind of structure surrounding it called the cell envelope made up of multiple layers which we'll discuss in detail and then inside you have these little baby ribosomes some bacterial chromosome which is in this kind of area you know in eukaryotic cells we have a a nucleus that actually surrounds the dna the actual chromosome with the eukaryotic cells and bacteria they don't have a nucleus so this bacterial chromosome or dna that we have here usually sits in this area of the actual bacteria cytoplasm so we call it the nucleoid so it's kind of like a nucleus so again remember there is no defined nucleus in a bacterial cell it sits in what's called a nucleoid type of area and then you have this small little circular dna in the bacteria some bacteria called a plasmid okay beautiful let's actually dig in though to these different things and talk about them a little bit more the first one we'll talk about is the appendages the things that are hanging off of the bacteria the first one is the flagella now the flagella i just want you to know the basic concept what is the purpose of the flagella and really it's like motility so the primary function of the flagella is for motility it basically allows for the bacteria to be able to move around in different areas it might create kind of a little corkscrew type of action now how does it do that well it's powered by atp so you need atp in order to power the flagella to be able to beat but when we look at the structure of the flagella you have a couple different components that you may be asked to annotate maybe on an exam of some form but there's multiple different rings you see this blue component here this blue component is actually called the basal body now the basal body is the part that has different types of protein rings that are kind of situated within the actual cell envelope so this component here is actually called the basal body okay that's what's kind of situated within the cell envelope the purple component here is called the hook of the flagella so this purple part here is called the hook of the flagella and then the last part is the filamentous portion here which is all of this portion here this is called the filament of the actual flagella so if you're asked to annotate the actual flagella this would be kind of the basic annotation of it okay so you know the fragiles for motility we know the basic kind of like structural annotation of the flagella now the next thing that you need to know about the flagella is also that some bacteria have different kind of like configurations of the flagella around their actual likes their self so if you look here you notice that this these bacteria here their flagella may be all over the place they might be situated on one side they may be stitching on both sides there's particular names that you have to know for these organisms that have these weird funky flagella configurations so let's talk about those whenever you have a actual flagella that's located on one pole of the bacteria we call this mono tricus so monotrichus it would be kind of an example of something like vibrio okay this would be an example of like vibrio cholera okay the next thing is if you have multiple flagella coming from one polar end of a bacteria we call this lofo tricus okay the next thing is if you and again lofo tricus could be kind of an example of potentially something like like a pseudomonas species so sometimes a pseudomonas species may be lophotricus the next thing is if you have flagella on both ends the polar ends of the bacteria we call this amphitrichus and this last one here we have flagella kind of extended all around the entire surface area of the bacteria this is called peritrigus and this would be a good example of like e coli okay so we have an understanding a very basic understanding of what i need you guys to know of the flagella it's designed for motility the basic structure it has the basal body you have the hook you have the filament it's powered by atp so it needs energy to be able to beat and move the bacteria from place to place you also should understand the different configurations of the actual flagella on bacteria monotrichus one flagella on one end low foot tricus multiple flagella on one polar end amphitrichus uflagel on both ends and peritricus throughout the entire surface area of the bacteria beautiful boom roasted let's move on to the next part of the appendages this is the fembre versus the pilots i kind of already alluded to this a little bit here's the big thing sometimes in textbooks it's referred to it's sometimes synonymous it's kind of the same thing but some of the more modern literature is actually saying that it's not really actually the same thing there is some definable differences between the fimbre and the pilots now what are some of those differences one of the big things to think about when we talk about the fembre and the pilots is that the fembre are actually shorter okay so the first thing that i want you to remember is that they are actually shorter and they're thinner in comparison to the pilots okay so that's one thing shorter and thinner the next thing that i want you guys to remember about this is that there is a larger number of fembrace spread along the bacterial surface area in comparison to the pilus another thing you know the pilots that you actually form it actually comes from a very specific kind of i'm sorry the fembray that you form that is actually formed from a very particular structure within the bacteria remember we were talking about the two different types of dna there was the bacterial chromosome and then there was the plasmid they're both dna the actual fembre is formed from the bacterial chromosome so that's what i want you to remember the actual bacterial chromosome will have particular genes that will be transcribed translated to make proteins that are involved in making these actual fembre so that's important now we have a basic understanding here fembre there's more of them they're shorter they're thinner and they're formed from the actual genes from bacterial chromosomes what do they do what's the whole purpose of these suckers the whole purpose of them is they allow for attachment or adherence to different types of cell surfaces so they're going to allow for attachment or adherence to cell surfaces okay beautiful now let's compare that to the pilots the pilots is actually again now we have a basic understanding we can just compare here based on this so if this had a large number what do you think a pilot has yeah less number i know you guys said it right so there's a lower number of pyly within this actual bacteria the other thing is if you look at them they're obviously not shorter they're longer and they're a little bit thicker okay here's another thing to add on when you actually look at the pilots if we were to actually kind of look at that the pilots actually comes from a part of the bacteria so let's say that we kind of draw the same kind of bacterial structure that we have over here the pilus actually comes from a different dna portion of the actual bacteria so the fembre came from the bacterial chromosome where do you think the pilus is actually coming from it's coming from the plasmid so the plasmid is the structure that has dna that whenever those genes are transcribed translated it'll then be translated into make proteins that are involved in forming the pilus okay so that's important to remember so some of the big differences between fembre and pilos is that fembre you have more number they're shorter they're thinner pilots there's a decreased number of them they're longer they're thicker the fembray the actual structure the proteins from it are made from bacterial chromosome pilus the proteins are made from the plasmid the other thing that's important to know about this is what is the basic function of the actual fem i'm sorry the pilots what is the big big function of this the big function of the pilots is it plays a role in a process called bacterial conjugation and we'll briefly discuss this in just a second but before i do that there's one more thing that helps us to differentiate fembre from pilos with fembray you can see these generally in both gram positive and negative bacteria and we'll talk about what the heck that means a little bit later whereas in someone who has pyly pyla are a little bit more particularly seen in gram-negative bacteria not so much in gram-positive bacteria okay all right so the basic understanding of the differences in their structure the differences in how they're made function for fembra is attachment of cell surfaces the plat the piluses for bacterial conjugation so let's briefly talk about what the heck bacterial conjugation is bacterial conjugation is a really cool process and it's a way by which bacteria can become resistant to certain types of drugs particularly like antibiotics i'll explain in a second so very very briefly let's say here we have a bacteria okay and this bacteria has a plasmid okay now this plasmid may have genes on it that it can get transcribed translated and make particular proteins or enzymes that can break down antibiotics and make those antibiotics less effective against that bacteria but since this bacteria maybe has that plasmid that allows for it to be able to make a particular pilot we call this plasmid that's in this bacteria that's going to help to make this pilus an f positive bacteria it means it's just a fertility positive now what happens is this plasmid will do a couple things it may transcribe get translated make proteins and then initiate the formation of a pilus okay so let's say here we have a pilus the other thing that it may do is not only help to make a pileus but also replicate and make another plasmid why because the goal is to be able to pass that plasmid onto another bacteria through the pilus the pilot is kind of like a little tunnel from bacteria to bacteria where you can pass genetic material from one to another so we'll see how that's done so again we have this bacteria it's fertility positive f positive meaning it has the plasmid that can make a particular protein or an enzyme that's important maybe in antibiotic resistance it'll make the pilus it'll then replicate that plasmid now now that it's done that let's actually see what this would look like so here's this plasmid the extra replicated version and then we're going to draw the pilots now the pilot is going to attach from one bacteria to another kind of like a little tunnel or channel now that that pilot is connected from this bacteria what is this bacteria called again since it has the plasmid we call this the f positive or the fertility positive this one does it have a plasmid present no so we call this f negative there's no fertility factor there there's no plasmid present but it's going to have it soon what happens is this plasmid helped to make the pilots it also replicated and so now that i have this pilot i can pass this actual plasmid that we just replicated onto this other bacteria that's f negative and then what's the result the result of this is that both of these bacteria are now f positive what's the whole goal of this i like just why the heck do i need to know this let's say just for an example this plasmid has a very particular protein that it's actually expressing maybe the plasmid is expressing a very particular type of enzyme and to give you an example of this let's say that this enzyme is called beta lactose beta-lactamase you know what it does it breaks down the beta-lactam ring and penicillin so it basically renders inhibits penicillin from its having its effect and penicillin is basically an antibiotic that's trying to prevent bacterial growth this bacteria may have this plasmid to make an enzyme like beta-lactamase to break down penicillin and make it resistant to the penicillin but this bacteria over here that was fertility negative it may have not had that actual plasmid to make that enzyme to make it what resistant to the penicillin so this bacteria says hey let me help you be resistant to penicillin i'll pass you on some of the genetic material that you need to make that betalactamase so that if penicillin comes near you you can break it down and so this is how bacteria can become resistant by passing on that genetic material through these dang piluses okay all right so we have a basic understanding of that beautiful so we now know flagella we understand fembra we understand pyli the next thing that we talked about very briefly that we didn't say we had a structure to show you is called an endospore endospores are basically specialized structures that are only found in certain types of bacteria okay there's a you know there's a bunch of them but the big ones that i want you guys to know about the endospores is they're they're found in very particular type of bacteria i'm just going to say the claustridium species and there's different types of clostridium species clostridium tetani right the tetanus clostridium perfringens uh there's again there's also clostridium difficile c diff so those types of bacteria have the ability to produce something called endospores another one is called bacillus anthracis so these bacteria have the ability to produce these really nasty things called endospores now what the heck are these endospores why are they produced why are they so nasty and why are they you know what's the significance of them within these particular bacteria so endospores basically are going to allow for bacteria to be resistant to very harsh environments so what do i mean let's write this down so that you guys know exactly like what i what i'm trying to tell you here so the whole purpose the function is it allows for the bacteria to be resistant to high temperature so if there's really high temperatures the endospore will help the bacteria to be able to thrive in high temperatures it may be able to thrive in like where there's lots of uv radiation maybe in environments where there's less nutrients or lots of chemicals or maybe even a really dry environment okay so basically the function of the endospore is to be able to still survive and become resistant to very harsh environments like high temperature lots of uv radiation lower nutrients maybe kind of a dry environment chemicals like antibiotics things of that nature so how does it do that is the question so again we know what type of bacteria this would form in we know the whole purpose of them is to function to become resistant in particular types of harsh environments now how does it do that but what happens here is you have this actual bacteria like the clostridium or the bacillus anthracus and it has this actual kind of like vegetative cell we call it inside of that vegetative cell you have your bacterial chromosome right which is basically the dna that's designed to be able to make enzymes and proteins that allow for the bacterial cell to function when it's exposed to these harsh environments high temperature lots of uv radiation certain types of chemicals or lower nutrient you know availability we needed to be able to you know accommodate and acclimate to that so what does it do first thing it does is it undergoes kind of replication process so we take that actual bacterial chromosome and we replicate it and so now we have two of these dnas right so we have some daughter dna then what we're going to do is is we're going to try to have this actual replicated dna kind of start like separating from one another and have them go to one end pole okay so we're going to have one of this actual daughter dna kind of congregate towards this end poll and have that mother bacterial dna kind of congregate to the other end pole once it does that and we kind of get them towards the impulse a cell membrane kind of partition or septa will form between the mother dna and this kind of daughter dna okay so now we form like a septa and technically this end here where we have that daughter dna we call that the four spore all right then what happens is something very interesting happens the actual membrane that's surrounding this mother dna wants to actually come around and kind of engulf or invaginate around the dna the daughter dna within the forespore and so it does that it actually kind of engulfs it and when it does that it forms like a double layered membrane around it so this actual kind of like mother cell component with the mother dna will kind of engulf and invaginate and wrap around that actual forespore portion and form a double layered membrane around that actual daughter dna then what happens is the mother dna starts to degrade by particular types of enzymes that'll get broken down okay then what happens now after we've formed that double layered membrane we actually want to put some particular types of sugar and protein content in between it and so then what happens is you put what's called a peptidoglycan layer between that double layered membrane okay so now we have a peptidoglycan layer there between the double layered membrane that's wrapped around the daughter dna that got invaginated by the actual or engulfed i should say by the mother cell component where the mother dna was and that got broken down then what happens is we actually take and have calcium kind of rush in to this endospore component so again it's going to have the peptidoglycan component in between that double layered membrane where their daughter dna is and there's going to be production of enzymes and proteins in that component of the endospore but what's going to happen now is we're going to have calcium kind of like rushing in we're gonna have calcium rushing in to this actual endospore now when calcium rushes in water starts leaking out kind of making it a little bit more of a drier environment in that area then after calcium rushes into the endospore we kind of pull water out of it what's the last thing that kind of happens here well it's kind of again recap here we have our double air membrane our double layered membrane contains within it what peptidoglycan layer the peptidoglycan layer then what happens you have calcium that rushes into the endospore which draws out water kind of drying out the endospore a little bit and then the last thing to happen is you want to put one more coating around this actual endospore that makes it again more resistant to harsher environments and so you put this kind of what's called a keratin coating this is called keratin coating around that actual spore and then lytic enzymes will actually break down the actual vegetative cell and release out that endospore that now can survive and thrive within these harsh environments because what does it have within it it has the dna that can make proteins and enzymes that allows for it to be able to function and then it has a peptidoglycan layer it has a dried out environment as a keratin coating everything that it needs to be able to really be able to be resistant in these all of these tough harsh environments which is pretty cool okay so that's something to think about okay we done nailed the appendages the specialized structures now let's go ahead and hit that cell envelope and the different components and functions there all right the next components we covered the appendages we covered the specialized structure of the endospore we know their structure we know their function we know the differences the next part is the cell envelope and this is really probably one of the more more important parts of this lecture is the cell envelope now the cell envelope i told you it was this big thick blue covering that we saw on this structure but in reality it's multiple different layers within that so what i want us to do is actually go through the layers of the cell envelope from the most outer part all the way to the most inner part systematically going through what is it made up of what does it do what's the significance of it so the first one which is the most outer component of the cell envelope is actually called there's two components it's actually the capsule or the slime layer they're relatively we kind of can put them in a category of what we call like the glycocalyx but let's kind of have a basic understanding of what the differences between these two are what's the significance of them the first one let's talk about is the capsule the capsule is actually made up of you see this green structure here it's actually made up of polysaccharides right but the polysaccharide layer here is really organized so what i want you to remember is a very organized polysaccharide coating that makes up that capsule when it's there okay so again organized polysaccharide network that is present within the capsule when you compare that to the slime layer the polysaccharide layering or network that's present here is a little bit more loose so let's actually kind of utilize those as kind of easy terms to help us to differentiate between capsule and slime layer it's a polysaccharide network organized in the capsule looser kind of a little bit more relaxed when it comes to the slime layer okay that's the basic concept what is the actual significance of the capsule and what is the significance or function of the slime layer the significance of the capsule is it actually acts as what's called a virulence factor so it acts as what's called a virulence factor you're like what the what did that mean man i got you dog the virulence factor is is it's basically the ability to promote infection okay so it has the ability to evade the immune system now how it do that what happens is the bacterial capsule makes it more difficult for certain types of white blood cells to phagocytose that bacteria so it actually decreases the phagocytosis kind of like efficacy if you will by white blood cells like macrophages and neutrophils and so it makes it harder for those white blood cells to be able to kind of latch on grab the bacteria and pull it in okay so that's one of the interesting thing about the capsules what i really really want you to know when it comes to significance in clinical medicine is that these capsules on bacteria can make them a little bit more nasty and cause some pretty nasty infections in certain populations and that's why we actually try to develop vaccines for some of these encapsulated bacteria that you guys should be getting you know what's the big ones that i want you to remember that we have vaccines for is what's called streptococcus pneumonia haemophilus influenza particularly type b and then what's called neseria meningitidis okay these are the three types of bacteria that have a capsule around them that we actually have vaccines for and are very important you know why these are very important because you know pertinent certain people who have like what don't have a spleen or they get their spleen removed for some particular reason maybe sickle cell anemia or you know hereditary spherocytosis some some kind if they don't have a spleen they're more susceptible to infections by encapsulated bacteria because the spleen is really good at removing those types of bacteria so again remember these bacteria that have capsules they're a little bit easier to evade the immune system by reducing that phagocytosis efficacy but we have vaccines to try to reduce that process there's other bacteria that have capsules that you know like you know pseudomonas e coli klebsiella salmonella but again these are big three that i want you to remember because these are the ones that we try to have vaccines for okay good slime layer we know it's a loose polysaccharide network what the heck is the significance of it the slime layer basically its function is to allow adherence to cell surface okay so it may be able to kind of like latch onto different types of cell surfaces within a host cell but what's even more interesting is it may be able to adhere to foreign substances foreign foreign substances or certain types of molecules so let me give you an example of that you know whenever somebody gets intubated and they put an endotracheal tube in it maybe it sits in there for a while because they have to remain intubated that endotracheal tube is a foreign substance and certain types of bacteria you know pseudomonas is a very classic example of this one so pseudomonas is a very classical example of a bacteria that loves to form slime layers if someone has like an endotracheal tube sometimes the pseudomonas bacteria can actually adhere to the endotracheal tube and form kind of a biofilm around and increase the risk of you know ventilator-associated pneumonias if you have a catheter that's placed into a vein like a central venous catheter okay a central venous catheter there's also a risk of bacteria kind of clinging on to that foreign catheter substance and leading to slime layers and biofilms forming on that and then lastly if there's kind of like a foley catheter or urethra catheter again that's a foreign substance that certain types of bacteria like pseudomonas may cling to and form biofilms around so that's kind of the big thing to remember when it comes to the actual slime layer now we covered that aspect we have the capsule we have the slime layer we know their differences in structure we know their function we know the significance of them let's move on to the next aspect and the next inner part of the cell envelope which is the outer membrane alright so we covered the capsule we covered the slime layer let's go to the next inner layer which is the outer membrane now outer membrane what is it made up of it's basically a phospho lipid bilayer but it has a very very specific type of structure and components within it which we'll annotate here in just a second what i do want you to really really really don't forget the outer membrane is only present in a particular type of bacteria it is only in gram-negative bacteria please don't forget that okay outer membrane only present in gram negative bacteria it's a phospholipid bilayer now let's talk about what is in that phospholipid bilayer that makes it so significant so we're going to take a gram negative bacteria parts of that actual outer membrane and zoom in on it when we do that we get this structure so obviously you can see your phospholipid bilayer here you can see the uh you know the glycerol head and you can see well the phospholipids and then you can see the fatty acid tails here some of the actual structures that are present in this outer membrane you have like porins right so these are basically just kind of like little proteins that allow for the transport of certain types of drugs or substrates or certain types of molecules to be able to transport in and out of the bacterial cell simple right but what's really important is that there is a endotoxin write that down this is a in do toxin that is present within this outer membrane and we're going to abbreviate this we call this lipopolysaccharides lipopolysaccharide lps the lipopolysaccharide is an endotoxin we'll talk about the significance of a second but we have to know what are the three components of the life of polysaccharide and which component of that lipopolysaccharide is actually the scary negative one three parts of it you have this red part this red part here is called lipid a okay and this is the nasty one and we'll talk about what why it's nasty in a second the next one is the pink part so we call this we're gonna call this the core polysaccharide okay so basically like a a polymer of sugar molecules and then this blue component which is extending out here okay this component here that's extending out is called the o antigen okay it's called the o antigen these three components make up the endotoxin the lipopolysaccharide now why is this significant the lipid a is actually the one that can activate or stimulate particular types of white blood cells you know like macrophages it can stimulate macrophages to release particular types of cytokines like interleukin-1 interleukin-6 tumor necrotic factor alpha and basically what these things can do is they can cause tons and tons and tons of problems they basically can potentially stimulate kind of a septic process because they can cause fevers they can cause a massive inflammatory reaction they can cause blood clots that lead to dic they can cause damage to the endothelium they can cause vasodilation and hypotension tons and tons of problems the core polysaccharide nothing particular to know about that but the o antigen whenever our immune system becomes activated they get exposed to this bacteria and they start to basically amount an immune response and produce antibodies you know where the antibodies love to attack they love to attack that o antigen so you want to remember that that is an antibody kind of attachment site on the actual bacteria so what i want you to remember is that antibodies attack or attach to the o antigen of the actual lipopolysaccharides okay beautiful that is the outer membrane what i want you to know phospholipid bilayer has porins has lipopolysaccharide structure which is an endotoxin three components of it lipid a core polysaccharide o antigen o antigen is a site for antibody attachment when the immune system is activated core polysaccharide nothing particular lipid a is the nasty component which has the ability to stimulate macrophages immune system cells to release massive amounts of cytokines particularly these three which can induce a septic vasodilatory process okay and big thing remember this is only in gram negative bacteria okay cool we covered the most outer layer capsule slime layer we covered the next one which is only gram negative bacteria which is the outer membrane what's the next part the next one which is just inside of the outer membrane is the cell wall all right so the next component is the cell wall so again we're going from outer to inner we got that capsule slime layer we got then the outer membrane cell wall cell wall one of the big things that i want you guys to know before we go over like what it's made up of because that's kind of a big topic is what is the kind of big function of it okay so we're kind of going a little bit backwards we've been talking about structure then function but just real quickly let's kind of reverse it on this one what's function and then we'll talk a little bit more about structure so function of the cell wall is obviously it gives shape to the bacteria it helps with kind of the structural integrity of the bacteria so when i talk about that it's involved with shape and integrity of bacteria okay kind of resistance against like osmotic kind of changes as well but one of the things is that's big with this and we'll have another video dedicated to kind of like bacterial nomenclature is it gives bacteria different shapes which is really cool so for example you can have a bacteria that's like circular like cocci or it's rod shaped like bacillus or it's kind of a mixture of coccy and basil so it's coxal bacillus you can have one that's kind of like comma shape which is like your vibrio and then you have the ones that are kind of like snake or kind of like spirally shaped we call spirilla and so we'll have a kind of a another video particularly focusing on bacterial nomenclature and things like that but i think it's one of the cool things about the cell walls it gives that shape which we have different types of nomenclature for which is pretty cool the other thing that i want you guys know about the cell wall is that this is present in both gram-positive and gram-negative bacteria so it's in both gram-positive and negative bacteria but we'll talk about in just a second there is a difference in the cell wall particularly the thickness of the cell wall when you're comparing it from grand positive to gram negative we'll talk about in a little bit so we know that it's involved in shape integrity you know resistance against osmotic changes and it's in both gram-positive gram-negative bacteria the next thing that i want you guys to know is actually like what is it made up of like some of the structure component of it and it's actually made of what's called a peptido glycan peptidoglycans you're like what the heck would that mean man so peptidoglycans there's two components in that in the name peptido so there's proteins peptides and glycans sugar so let's focus on the sugar portion the glycan there's two components that we actually polymerize and make these glycan backbones and this one here in pink we're going to call i'm just picking there's no particular reason i'm just no rhyme reason just picking it the pink one we're going to call in acetyl muramic acid which we call nam that's one of the actual sugar molecules and the other one here in this kind of blue color here is called in acetyl glucosamine which we're going to just abbreviate as nag what happens is these nags enamels get polymerized together and when they do that they make this glycan or sugar backbone then what happens is there's a special type of enzyme called a transpeptidase which is kind of a domain on a special type of enzyme we'll talk about later called a penicillin binding protein and what that protein does is is it kind of links together these glycan backbones so this is your peptide chains which are going to be linking the glycan backbones together so that's what i want you to remember is when we talk about the peptidoglycan layer of the cell wall it's made up of nags and names that are polymerized to make a glycan backbone and peptide chains that are formed by a very specific enzyme which is called the transpeptidase which is a domain on the penicillin binding proteins that cross link them together beautiful one of the big things though let's briefly talk about here is kind of like what is some of another significant point about this peptidoglycan layer well one of the big things i want you guys to remember is that there is another structure that's kind of like similar to the lipopolysaccharides remember the lps is the endotoxin only found in the outer membrane which is only found in gram-negative bacteria you know gram-positive bacteria they have something that's kind of like homologous to that and so in that they have a molecule called lipotocoic acid which we're going to abbreviate as lta lipoic acid is this purple structure that extends from the inner membrane and extends all the way through the cell wall what is the significance of the lipochoic acid that extends through the cell wall you know what it loves to do it loves to be able to stimulate white blood cells like macrophages and stimulate these macrophages to release particular types of cytokines like interleukin-1 interleukin-6 tumor chronic factor alpha which have the ability to produce fever hypotension increase inflammation vasodilatory effects and potentially kind of cause a septic process so that is your lipotocoic acid now your pile like well what is this pink thing that doesn't touch the inner membrane but it's still kind of incorporated within that cell wall or peptidoglycan layer glad you asked this thing here is not connected to the lipid membrane but it is a kind of like fatty acid structures we call this a tachoic acid okay tachoic acid so tachoic acid is a part of this structure that extends just through the cell wall doesn't touch the inner membrane light petrichoric acid touches the inner cell membrane extends through the cell wall and involved in stimulating this kind of interleukin one interleukin 6 tuna chronic factor alpha process last quick thing here just because i said that there was a small difference here in peptidoglycan layer what i want you to remember when it comes to gram positive versus gram negative gram positive versus gram negative with the peptidoglycan layer gram-positive has a thicker peptidoglycan layer and gram-negative bacteria has a thinner peptidoglycan layer please don't forget that okay so we have cell wall maintains structural integrity prevents like osmotic kind of changes and influences cell shape found in both gram-positive gram negative bacteria it's made up of peptidoglycans which is made up of n-acetylglucosamine and acetyl-muramic acid which is sugar molecules that are polymerized to make a glycant backbone cross-length through trans-peptides and again gram-positive has a thicker peptidoglycan layer gram-negative has a thinner peptidoglycan layer and again another significance is that only in oh i gotta make sure you guys remember this only in gram positive bacteria do they have this lipotocoic acid that is involved in this kind of interleukin-1 interleukin-6 tumor chronic factor alpha process that can cause kind of a septic process it's kind of analogous to the lps that was in gram-negative bacteria so only gram-positive bacteria let's actually make this look a little bit nicer gram-positive bacteria has that lipotocoic acid all right beautiful roasted let's move on to the next component here which is the periplasm all right so the next part so again we've covered capsule slime layer from outer to the outer membrane to the cell wall to the periplasm now the periplasm is the next structure now here's the big thing the periplasm how do you define it it is the space between i'm going to abbreviate this the outer membrane which is only present in what type of bacteria okay negative bacteria and the inner membrane which we haven't gotten to yet but this is present in gram-positive and gram-negative bacteria it's that space between now what was in that space that we talked about if you guys remember outer membrane and gram-negative bacteria and then we hit cell wall so that's our peptidoglycan layer with the nam nag and trans-peptide uh bonds there compare the peptide bonds formed by the transpeptidases in the periplasmic space okay which is the space between the outer membrane and inner membrane which obviously which bacteria only have outer membranes gram-negative so you can only have a periplasmic space and gram-negative bacteria therefore by that definition what is the significance of it you see this little like dude little bee dude this is a very special enzyme and this enzyme we talked about a little bit over here before it's called a beta lactamase remember that when we talked about the pilus you can actually like have those plasmids that actually have genes that can be transcribed translated make proteins like beta-lactamase that make things resistant to antibiotics and you can pass that on to other bacteria to make them more resistant beta-lactamase sits within the periplasmic space so you know whenever somebody takes like for example they have a gram negative bacteria and then they take a drug like penicillin and penicillin has to get through the outer membrane through the peptidoglycan layer and what happens is this beta lactamase will come and say hey penicillin i'm going to inhibit you and then render it ineffective and being able to you know prevent or inhibit the cell wall growth so that's kind of the cool thing about the beta-lactamase so again periplasm only technically found in gram-negative bacteria since only gram-negative bacteria of outer membrane and inner membrane and the definition is the space between outer and inner membrane in that space is the beta-lactamase allowing for resistance to antibiotics like penicillin boom roasted move on to the last component of the cell envelope what is the most inner component the inner membrane baby inner membrane what is it made up of it is a phospho lipid bilayer now within that phospholipid bilayer there's obviously different types of proteins so different types of like porins there's different types of enzymes that are involved in like you know oxidative metabolism or different types of dna replication or other enzymatic metabolic processes but one of the big proteins that i need you guys to definitely remember is this one right here that's shaped like a p this right here this bugger is called the penicillin binding protein now the penicillin binding protein we talked about a little bit over here and we can actually kind of refer to it while we're here the penicillin binding protein has kind of like one like domain like a little like like imagine like a little arm out here that has what's called a trans peptidase function and what does that mean it means you see these bonds here that are formed the peptide bonds that are formed between the glycan backbones that's actually by that enzyme which is kind of a domain on the penicillin binding protein which is found where on the inner membrane inner membrane is that found on gram-positive bacteria gram negative bacteria or both well all of them have it right so both gram-positive and gram-negative bacteria have this inner membrane so they both have penicillin binding proteins the whole reason this is significant is when you give a drug like penicillin what does penicillin do penicillin's design is to be able to inhibit that transpeptidase portion on the penicillin binding protein if you inhibit this portion can you crosslink the actual glycan backbones that stabilize the cell wall no if you can't stabilize that cell wall are you going to be able to grow it no you'll start losing the structural integrity you'll start losing the ability to resist against osmotic fluctuations and then what happens the actual bacteria can die and so that's one of the big things to think about is the significance of this penicillin binding protein okay boom roasted baby we done did it that is the cell envelope now the absolute most important thing to take away from this is you guys are probably going to get a question on the exam about what are the differences in the cell envelope between gram-positive and gram-negative bacteria let's quickly and i mean quickly review what we have just talked about this entire time here's your gram positive bacteria here's your gram negative bacteria from outer to inner they both can have what a capsule or a slime layer then you go to next thing okay what's the next thing that we hit we said outer membrane outer membrane is only present in gram-negative bacteria not present here in gram-positive bacteria what's on the outer membrane that was so significant and important we said it's a phospholipid bile that had porons that allowed for things to move in and out but the big thing was this thing sticking out here called the lps the endotoxin called the lipopolysaccharides you don't see that on gram-positive bacteria but you do see that on gram-negative bacteria okay what's the next thing after the outer membrane then we had cell wall cell wall is the peptidoglycan component which is made up of nags which is your glycan backbones and your peptide bonds which are cross linking them so here's your peptidoglycan layer here which is component of the cell wall and then here in the gram-negative bacteria what do you notice in the difference of thickness here gram-positive they got a thick peptidoglycan layer and then in the gram-negative they got a baby thin peptidoglycan layer so that's another big significant point here the other thing here that's important is that in that cell wall in gram-positive bacteria they have this structure that extends from the actual inner membrane or from the cell wall only in gram-positive bacteria what is this thing here called the lipotechoic acid or tochoic acid do you see that here in the gram-negative bacteria no so there's no lypotech acid or techoic acid present in the gram-negative bacteria the next thing is we had a periplasmic space do you see a periplasmic space here in gram positive no because they don't have an outer membrane it's the space between outer membrane and inner membrane which one has the outer membrane gram-negative bacteria so it has to be the space between here what's in that space oh a little beta-lactamase enzyme and that's only in gram-negative bacteria and then the last thing here is that you have the gram-positive bacteria and gram-negative bacteria they both have the inner membrane and they both have the penicillin-binding proteins and remember the last thing i told you guys they both can have flagella but which one did i tell you that the pilots is primarily most common in gram-negative bacteria and what was this example that we used as gram-negative bacteria being able to transmit kind of resistance to antibiotics the beta-lactamase which one has beetalectomies gram negative bacteria does it have a hearing ground positive no so we now understand and we have a pretty good understanding of gram-positive versus gram-negative bacteria now we have to do to just cap it all off is talk about the actual protocol procedures that you need to understand to do in the lab about how to do the gram staining procedure and microscopically visualize what is the difference between gram positive and gram-negative bacteria let's hit that all right so now what we have to talk about is the gram-staining procedure you guys need to know this because when you guys are in the lab you'll have to know the steps to be able to perform in order in sequence why you're doing it in this particular sequence and then after you know how to do this procedure step by step you should be able to identify microscopically which one is gram-positive and which one's gram-negative bacteria based upon the staining or the color of it and then which ones kind of fall into this you know atypical category of bacteria knowing which one those are all right so let's go through this process you take you grow your bacteria in whatever culture you've done it you take that you scoop it onto a slide after you've applied the bacteria onto the slide which is your step one you're then going to take and heat up the slide when you heat up the slide the whole purpose of that is to get the bacteria to fixate to the slide okay so the second step is to heat up the slide to get the bacteria to fixate once the bacteria has been fixated to the slide the third step is you're going to apply what's called a particular type of stain called a crystal violet stain which obviously gives off a violet purplish type of color you apply the stain to the slide what happens is the bacteria that are on the slide should suck up that crystal violet into the peptidoglycan layer and they should stain purple which the bacteria have peptidoglycan layers both gram-positive and both gram-negative bacteria so let's imagine for a second you looked underneath you looked at the microscope you pulled it after you've applied the the crystal bile you looked in the microscope and you looked to see what the bacteria look like all of them should stain purple because they've taken up that crystal violet color why is that let me explain this for a second here if you look here we have on this side our gram positive and here we have our gram negative bacteria you give the crystal violet now the crystal violet is just going to get soaked up into the peptidoglycan layer now the gram positive has a very thick peptidoglycan layer so it has lots of area that you can have that actual crystal violet soak up into okay also here's another interesting thing gram-negative bacteria have an outer membrane which makes it a little bit more like selectively permeable so less crystal violet will be able to get into the peptidoglycan layer because it's going to have to go through that porins so less of it will get in there and another additional fact here is that there's less peptidoglycan so there's less actual like amounts of crystal violet that's going to be within that peptidoglycan layer but nonetheless there's peptidoglycan that's saturated within this actual there's crystal violet sorry stain that's saturated within this peptidoglycan layer of both gram positive and gram-negative bacteria okay the next step after we've applied the crystal violet is we don't want that crystal violet to kind of like leech out and so how do we kind of like cement or keep that crystal violet kind of like fixated and stuck in that area of the peptidoglycan component of the grand positive and negative bacteria we apply a mordant and this mordant that we're going to have here in this reddish color here is going to be called iodine it's called a mordant and all that means is let's say here we have again our gram positive bacteria our gram negative bacteria and we can identify that based upon thick bipedal glycogen thin peptidoglycan and gram negative only has the outer membrane gram positive does not right we know that the crystal violet in step three here has been saturated in that actual peptidoglycan layer we know it's also saturated here within that gram-negative layer what the iodine does is it kind of latches onto the crystal violet and keeps it really kind of like locked into that peptidoglycan layer so it kind of acts like a little bit of a cement to keep some of that crystal violet in the peptidoglycan layer okay so that's our fourth step now the fifth step is the interesting step the fifth step is we apply something called like ethanol or alcohol some kind of alcohol-based substance maybe even like acetone sometimes is applied but it's an ethanol wash right and what you do is you take like a bottle of like you know some ethanol or acetone and you keeps you know you squirt that over for a certain period of time over the slide and you're trying to wash some of the crystal violet out of the peptidoglycan layer now the theory behind how this actual like ethanol does this is it may compress the actual peptidoglycan layer and also may have like a little bit of a dissolving effect or put holes within kind of like phospholipid bilayers to allow for some of that crystal violet to be able to leech out but either way the whole design of the ethanol is to kind of suck some of the crystal violet or wash some of the crystal violet out of the peptidoglycan layer now come here for a second and realize what do we have so far going back to this point here again here is our gram positive here's our gram-negative bacteria we have that peptidoglycan layer filled with our crystal violet here and that gram positive we have it filled here within the gram negative we have the mordant trying to kind of keep it situated in here which is the iodine and then we apply the ethanol when you apply the ethanol it is going to pull some of that crystal violet out of the grand positive bacteria it's going to pull some of it out but it shouldn't pull ton as much out as you as you actually think the reason why is why you have saturated that peptidoglycan layer with tons of crystal violet there's tons of it and then you have some of it pretty fixated really well in there with the iodine as the mordant the gram negative bacteria though there wasn't really much crystal violet in there to begin with because you had a very thin peptidoglycan layer there's not a crystal violet there present in general like a mount and also there was less of that crystal violet probably able to get in to the actual peptidoglycan layer because of the outer membrane so when you apply ethanol to the gram negative bacteria it's going to wash out the very little amounts of crystal violet that you do have you're going to have lots of crystal vitamin gram positive not as much in gram negative so when you apply that ethanol wash it is going to suck out tons and tons of that crystal violet that you had there and so effectively what should happen is if you took at that moment looked at the slide after you applied the ethanol wash what should happen the bacteria that were gram positive should still be retaining that crystal violet unless you freaking applied so much ethanol that you literally washed all of it out so sometimes if you do apply too much ethanol for too long period of time you can leech out enough crystal violet out of the grand positive bacteria and it won't stain purple that's why you have to do it for you know you don't do it very long but once you have that ethanol wash and you look under the microscope the gram-positive bacteria should still be retaining some of that crystal violet so what color should they be under the microscope purple the gram negative bacteria in theory if you apply the ethanol wash and yank some of that crystal violet out the very little crystallite that you had there there shouldn't really be any purple color there so they shouldn't have any purple color they shouldn't stain purple and that will be your gram negative bacteria but we still can't identify them because they're not staining a particular color that makes them obvious on the slide so how can we make it obvious that that the ones that aren't actually staining it there is some gram negative bacteria on that slide how do i identify them because i don't have a color that makes them pop or stand out well that's where the next thing comes in the next thing is we apply what's called a counter stain the counter stain is we use something which is this purple structure we apply what's called the counter stain we apply this molecule called safranin what safranin does is is it should soak into the peptidoglycan layer that doesn't have any crystal violet so wherever there's no crystal violet that saffron should soak into that peptidoglycan layer let's think here here's our gram positive bacteria here's our gram-negative bacteria we said that some of the crystal violet may get washed from the gram-positive bacteria but there should be still a decent amount that's actually retained there keeping it purple you washed out the crystal violet whenever you did the ethanol wash from the gram-negative bacteria but if you give that saffron in that should soak up into the peptidoglycan layer that does not have any crystal violet it should do what give the color of that stain when you look at it under the microscope so if i look at it under the microscope now the gram negative bacteria that didn't weren't staining previously should stain pink why because they soaked up that safranin and that will tell me what type of bacteria i have so at the end of it after you've applied your counter stain or your saffron and you look under the microscope the bacteria that stain pink mean that they retained the actual counter stain or the safranin has to be the gram-negative bacteria and then the ones that retained the actual crystal vial throughout the entire time is the gram-positive bacteria i hope that makes sense okay the last thing is that sometimes there's bacteria that don't really stain like an obvious color and so we kind of fit them into this weird like they're kind of considered gram-negative bacteria but they don't really stain and so we actually call them atypical bacteria all i want you to know is the names of these atypical bacteria and that's it all right so again what i really want you to remember is that these atypical bacteria are technically clumped within the category of gram-negative bacteria because they don't stain a particular grit like crystal violet color they don't really stain in general but these atypical bacteria you should actually remember them because again they're not really going to have that classic gram-positive gram-negative stain and so there's a mnemonic that helps us to be able to remember this it's these atypical microbes usually lack color because microbes barely eat ramen okay it's a random one but it it may help you to remember it so the t in these stands for trypanema so trypanemapolitum right which is the bacteria that causes syphilis the a for atypical stands for ana plasmosis the m in microbes can be micro plasma the u and usually is for urea plasma and let's move on over here to these the l in lac is for leptospira and it can actually be a double you can actually consider it legionella the c in color would be for chlamydia the b and because can be for bartonella the m in microbes is there so there's another m this was mycoplasma this is mycobacteria the b and barely there's another b this was for bartonella that because the barely can be borrelia like the berelia bergdorferi and lime's disease the e for eat is erlichia like erlichiosis from the tick bite and r is for ramen which is rickettsia which again is another kind of species of ticks okay bacteria from ticks so again this would cover your atypical bacteria again quick reminder of these these are technically within that gram-negative category they don't really fit in that actual staining process of purple or crystal via i'm sorry crystal violet or that pink kind of saffron in color and again it's trypanema anaplasmosis mycoplasma urea plasma leptospira or lesionella chlamydia bartonella mycobacteria borrelia erlichia and rickettsia that covers our discussion on the structure and function of bacteria all right ninja nerds in this video we talk about the structure and function of bacteria as well as the gram staining procedure i hope it made sense i hope that you guys enjoyed it i hope you learned a lot as always ninja nerds until next time [Music] you