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Bacteria | Structure and Function — Transcript

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0:07what's up ninja nerds in this video
0:08we're going to be talking about the
0:10structure and function of bacteria
0:13before we get started if you guys like
0:14this video you benefit from it please
0:16hit that like button comment down in the
0:18comment section and please subscribe
0:20also if you want some awesome
0:22illustrations and notes to follow along
0:24with this video check that down in the
0:26description box below alright ninja
0:27nerds let's get into it all right
0:29engineers when we talk about the
0:31structure and function of bacteria we
0:32should have a basic understanding of
0:34just a little bit about the structure so
0:35if we take this nice beautiful little
0:37diagram here
0:38uh of a bacteria we should kind of point
0:41out some of the different components of
0:43it we're going to go into a little bit
0:44more detail on those structures a little
0:46bit more about what they're made up of
0:47what they do what's the significance of
0:49it but let's just have a basic idea of
0:51the basic anatomy or structure of this
0:53bacteria
0:54so first thing is let's talk about some
0:55of the things that are coming off of the
0:57bacteria which we're going to refer to
0:58as appendages
1:00some of these things that you guys want
1:01to know is first one is this big old
1:04orange thing that's popping out off this
1:06thing what is this structure here called
1:08do you guys know this is called the
1:10flagella okay so this structure right
1:12here is called your flagella
1:16and obviously we'll talk about what that
1:18does and what it's made up of in just a
1:19second
1:20these little brown things the tiny
1:22little brown things that are coming off
1:25of this actual bacteria here these
1:27little guys here are called your fimbre
1:32and then this big one here this longer
1:34one which there's less frequent of is
1:37called your pilous
1:39so these are some of the big appendages
1:42that i want you guys to remember big
1:43orange thing flagella little guys with
1:45numerous amounts of them is fembre and
1:47this long one which is usually less
1:49frequent a little bit longer is your
1:51pileus okay
1:53now the next thing that i want you guys
1:55to know we're not going to actually have
1:56it visualized inside of this bacteria
1:59but some bacteria we'll talk about in a
2:00second can have these structures inside
2:02of them called endospores we'll talk
2:04about that a little bit later though
2:06all right the next thing is basically
2:09the actual kind of like cell envelope
2:12okay this bacteria has this big thick
2:14kind of like blue wall around it
2:17and that big thick blue wall that we're
2:19going to discuss in pretty good detail
2:21later is made up of multiple different
2:23components and that's called the cell
2:26envelope
2:27and again we'll kind of dig into that
2:29talk about the multiple layers of the
2:31cell envelope what they're made up of
2:32what's their function
2:34okay so so far we have the appendages
2:36we'll talk about a specialized structure
2:38called the endospore which isn't
2:40pictured here then we have the covering
2:43around the actual bacteria which is this
2:45big thick kind of blue wall called the
2:47cell envelope made up of multiple
2:49different layers
2:50inside of the bacteria though you'll
2:53actually notice a couple different
2:55things you have all these like little
2:57sorry not blue red dots these red dots
3:00are all of your ribosomes so you have a
3:02bunch of different ribosomes baby little
3:04ribosomes present inside of the actual
3:06bacteria
3:07and then you have a big kind of purple
3:09entanglement of dna
3:12this right here is actually called the
3:14bacterial chromosome okay so this is
3:17your bacterial chromosome okay so we're
3:20just going to call this the bacterial
3:24chromosome
3:26and then this little guy right here is
3:28another piece of dna actually present in
3:31the bacteria but it's not a part of the
3:33bacterial chromosome and only actually
3:35some bacteria have this
3:37and it's a little circular small piece
3:39of dna and this is called
3:43your plasmid and again we'll discuss
3:44this a little bit later as well
3:46but these are some of like the basic
3:48things that i want you guys to know
3:49about the actual bacterial structure
3:52again real quick recap appendages give
3:54the flagella which is this orange
3:55structure little guys coming off of the
3:57fembre the long ones which are usually
4:00less a number of them is the pilus
4:03you have this big blue kind of structure
4:05surrounding it called the cell envelope
4:06made up of multiple layers which we'll
4:07discuss in detail and then inside you
4:10have these little baby ribosomes some
4:12bacterial chromosome which is in this
4:14kind of area you know in
4:16eukaryotic cells we have a
4:18a nucleus that actually surrounds the
4:20dna the actual chromosome with the
4:22eukaryotic cells and bacteria they don't
4:24have a nucleus so this bacterial
4:27chromosome or dna that we have here
4:29usually sits in this area of the actual
4:31bacteria cytoplasm so we call it the
4:33nucleoid so it's kind of like a nucleus
4:36so again remember there is no defined
4:37nucleus in a bacterial cell it sits in
4:40what's called a nucleoid type of area
4:42and then you have this small little
4:43circular dna in the bacteria some
4:45bacteria called a plasmid
4:47okay beautiful
4:49let's actually dig in though
4:51to these different things and talk about
4:53them a little bit more
4:54the first one we'll talk about is the
4:55appendages the things that are hanging
4:57off of the bacteria the first one is the
4:59flagella now the flagella i just want
5:02you to know the basic concept what is
5:04the purpose of the flagella and really
5:07it's like motility so the primary
5:09function of the flagella
5:11is for motility it basically allows for
5:14the bacteria to be able to move around
5:17in different areas it might create kind
5:19of a little corkscrew type of action
5:21now how does it do that well it's
5:23powered by atp so you need atp in order
5:26to power the flagella to be able to beat
5:28but when we look at the structure of the
5:30flagella
5:32you have a couple different components
5:33that you may be asked to annotate maybe
5:35on an exam of some form but there's
5:38multiple different rings you see this
5:39blue component here this blue component
5:41is actually called the basal body now
5:44the basal body is the part that has
5:46different types of protein rings that
5:48are kind of situated within the actual
5:50cell envelope so this component here is
5:52actually called the basal
5:55body okay that's what's kind of situated
5:57within the cell envelope
6:00the purple component here is called the
6:02hook
6:03of the flagella so this purple part here
6:05is called the
6:06hook
6:08of the flagella
6:09and then the last part is the
6:11filamentous portion here which is all of
6:13this portion here this is called
6:15the filament
6:17of the actual flagella so if you're
6:19asked to annotate the actual flagella
6:20this would be kind of the basic
6:22annotation of it okay so you know the
6:23fragiles for motility we know the basic
6:26kind of like structural annotation of
6:28the flagella now the next thing that you
6:30need to know about the flagella
6:32is also that some bacteria have
6:34different kind of like
6:35configurations of the flagella around
6:37their actual likes their self so if you
6:39look here you notice that this these
6:41bacteria here their flagella may be all
6:43over the place they might be situated on
6:45one side they may be stitching on both
6:46sides there's particular names that you
6:48have to know for these organisms that
6:50have these weird funky flagella
6:52configurations so let's talk about those
6:55whenever you have a actual flagella
6:57that's located on one pole of the
6:59bacteria we call this
7:02mono
7:04tricus
7:06so monotrichus it would be kind of an
7:09example of something like vibrio okay
7:13this would be an example of like vibrio
7:15cholera okay
7:17the next thing is if you have multiple
7:20flagella coming from one polar end of a
7:22bacteria we call this
7:26lofo
7:28tricus
7:30okay
7:31the next thing is if you and again lofo
7:34tricus could be kind of an example of
7:37potentially something like like a
7:38pseudomonas species so sometimes a
7:40pseudomonas
7:45species may be lophotricus
7:47the next thing is if you have flagella
7:49on both ends the polar ends of the
7:52bacteria we call this amphitrichus
7:59and this last one here we have flagella
8:00kind of extended all around the entire
8:02surface area of the bacteria
8:04this is called
8:06peritrigus
8:09and this would be a good example of like
8:10e coli
8:13okay so we have an understanding a very
8:15basic understanding of what i need you
8:16guys to know of the flagella it's
8:18designed for motility the basic
8:20structure it has the basal body you have
8:22the hook you have the filament it's
8:24powered by atp so it needs energy to be
8:26able to beat and move the bacteria from
8:28place to place
8:29you also should understand the different
8:31configurations of the actual flagella on
8:33bacteria monotrichus one flagella on one
8:36end low foot tricus multiple flagella on
8:38one polar end amphitrichus uflagel on
8:41both ends and peritricus throughout the
8:43entire surface area of the bacteria
8:45beautiful boom roasted let's move on to
8:48the next part of the appendages this is
8:50the fembre versus the pilots i kind of
8:52already alluded to this a little bit
8:54here's the big thing sometimes in
8:56textbooks
8:57it's referred to it's sometimes
8:59synonymous it's kind of the same thing
9:02but some of the more modern literature
9:04is actually saying that it's not really
9:05actually the same thing there is some
9:07definable differences between the fimbre
9:10and the pilots now what are some of
9:11those differences
9:13one of the big things to think about
9:14when we talk about the fembre and the
9:16pilots is that the fembre are actually
9:20shorter okay so the first thing that i
9:22want you to remember is that they are
9:23actually
9:25shorter
9:26and
9:28they're thinner
9:30in comparison to the pilots okay so
9:32that's one thing shorter and thinner
9:35the next thing that i want you guys to
9:37remember about this
9:38is that there is
9:40a larger
9:42number
9:43of fembrace spread along the bacterial
9:46surface area in comparison to the pilus
9:50another thing
9:52you know the pilots that you actually
9:53form it actually comes from a very
9:56specific kind of i'm sorry the fembray
9:58that you form that is actually formed
10:00from a very particular structure within
10:02the bacteria remember we were talking
10:03about the two different types of dna
10:06there was the bacterial chromosome and
10:07then there was the plasmid they're both
10:09dna
10:11the actual fembre is formed from the
10:13bacterial chromosome so that's what i
10:16want you to remember the actual
10:17bacterial chromosome
10:21will have particular genes that will be
10:23transcribed translated to make proteins
10:25that are involved in making these actual
10:28fembre so that's important
10:30now we have a basic understanding here
10:32fembre there's more of them they're
10:34shorter they're thinner and they're
10:36formed from the actual genes from
10:38bacterial chromosomes what do they do
10:40what's the whole purpose of these
10:41suckers
10:42the whole purpose of them is they allow
10:44for attachment or adherence to different
10:47types of cell surfaces so they're going
10:49to allow for attachment
10:53or adherence
10:55to cell
10:57surfaces
10:59okay beautiful
11:01now let's compare that to the pilots the
11:03pilots is actually again now we have a
11:05basic understanding we can just compare
11:07here based on this so if this had a
11:09large number what do you think a pilot
11:10has
11:12yeah less number i know you guys said it
11:14right so there's a lower
11:16number
11:17of pyly within this actual bacteria
11:21the other thing is if you look at them
11:23they're obviously not shorter they're
11:26longer and they're a little bit thicker
11:30okay
11:31here's another thing to add on
11:34when you actually look at the pilots if
11:37we were to actually kind of look at that
11:39the pilots actually comes from a part of
11:42the bacteria so let's say that we kind
11:43of draw the same kind of bacterial
11:45structure that we have over here
11:47the pilus
11:50actually comes from a different dna
11:53portion of the actual bacteria so the
11:55fembre came from the bacterial
11:57chromosome where do you think the pilus
11:59is actually coming from it's coming from
12:01the plasmid so the plasmid
12:05is the structure that has dna that
12:07whenever those genes are transcribed
12:09translated it'll then be translated into
12:12make proteins that are involved in
12:14forming the
12:15pilus okay so that's important to
12:17remember so some of the big differences
12:20between fembre and pilos is that fembre
12:22you have more number they're shorter
12:24they're thinner pilots there's a
12:26decreased number of them they're longer
12:27they're thicker the fembray the actual
12:30structure the proteins from it are made
12:32from bacterial chromosome pilus the
12:34proteins are made from the plasmid
12:37the other thing that's important to know
12:39about this
12:40is what is the basic function
12:43of the actual fem i'm sorry the pilots
12:45what is the big big function of this
12:47the big function of the pilots
12:50is it plays a role in a process called
12:53bacterial
12:56conjugation
12:58and we'll briefly discuss this in just a
13:01second but before i do that there's one
13:03more thing that helps us to
13:05differentiate
13:06fembre from pilos
13:09with fembray you can see these generally
13:13in both
13:14gram
13:16positive
13:18and negative bacteria and we'll talk
13:20about what the heck that means a little
13:21bit later
13:23whereas in someone
13:25who has pyly pyla are a little bit more
13:28particularly seen
13:31in gram-negative bacteria not so much in
13:33gram-positive bacteria
13:35okay all right so the basic
13:37understanding of the differences in
13:38their structure the differences in how
13:40they're made function for fembra is
13:43attachment of cell surfaces the plat the
13:45piluses for bacterial conjugation so
13:47let's briefly talk about what the heck
13:49bacterial conjugation is
13:51bacterial conjugation is a really cool
13:53process and it's a way by which bacteria
13:55can become resistant to certain types of
13:58drugs particularly like antibiotics i'll
13:59explain in a second
14:01so very very briefly
14:03let's say here we have a bacteria okay
14:05and this bacteria has
14:07a plasmid
14:08okay
14:10now this plasmid may have genes on it
14:13that
14:14it can get transcribed translated and
14:15make particular proteins or enzymes that
14:17can break down antibiotics and make
14:19those antibiotics less effective against
14:22that bacteria
14:24but
14:24since this bacteria maybe has that
14:26plasmid that allows for it to be able to
14:28make a particular pilot we call this
14:31plasmid that's in this bacteria that's
14:33going to help to make this pilus an f
14:36positive bacteria it means it's just a
14:37fertility positive
14:40now what happens is this plasmid will do
14:42a couple things it may transcribe get
14:44translated make proteins and then
14:46initiate the formation of
14:49a pilus
14:50okay so let's say here we have a pilus
14:53the other thing that it may do
14:56is not only help to make a pileus but
14:58also replicate and make another plasmid
15:02why because the goal is to be able to
15:04pass that plasmid onto another bacteria
15:08through the pilus the pilot is kind of
15:09like a little tunnel from bacteria to
15:11bacteria where you can pass genetic
15:13material from one to another so we'll
15:15see how that's done so again we have
15:17this bacteria it's fertility positive f
15:20positive meaning it has the plasmid that
15:22can make a particular protein or an
15:25enzyme that's important maybe in
15:27antibiotic resistance
15:29it'll make the pilus it'll then
15:31replicate that plasmid now now that it's
15:34done that let's actually see what this
15:35would look like so here's
15:36this plasmid the extra replicated
15:38version
15:39and then we're going to draw the pilots
15:41now the pilot is going to attach
15:43from one bacteria to another kind of
15:46like a little tunnel or channel
15:48now that that pilot is connected
15:51from this bacteria what is this bacteria
15:53called again since it has the plasmid we
15:55call this the f positive or the
15:57fertility positive this one does it have
15:59a plasmid present
16:01no
16:01so we call this
16:03f negative there's no fertility factor
16:05there there's no plasmid present but
16:07it's going to have it soon
16:09what happens is
16:10this plasmid helped to make the pilots
16:12it also replicated and so now that i
16:15have this pilot i can pass
16:18this actual plasmid that we just
16:20replicated onto this other bacteria
16:23that's f negative
16:24and then what's the result the result of
16:27this is that both of these bacteria are
16:28now
16:30f positive what's the whole goal of this
16:33i like just why the heck do i need to
16:35know this let's say just for an example
16:39this plasmid has a very particular
16:41protein that it's actually expressing
16:43maybe the plasmid is expressing a very
16:46particular type of enzyme and to give
16:48you an example of this let's say that
16:50this enzyme is called beta
16:53lactose beta-lactamase you know what it
16:55does it breaks down the beta-lactam ring
16:58and penicillin
16:59so it basically renders inhibits
17:02penicillin
17:03from its having its effect and
17:04penicillin is basically an antibiotic
17:06that's trying to prevent bacterial
17:07growth
17:09this bacteria may have this plasmid to
17:11make an enzyme like beta-lactamase to
17:13break down penicillin
17:14and make it resistant to the penicillin
17:17but this bacteria over here that was
17:19fertility negative it may have not had
17:21that actual plasmid to make that enzyme
17:24to make it what
17:26resistant to the penicillin so this
17:29bacteria says hey let me help you be
17:31resistant to penicillin i'll pass you on
17:33some of the genetic material that you
17:34need to make that betalactamase so that
17:36if penicillin comes near you you can
17:38break it down and so this is how
17:39bacteria can become resistant by passing
17:42on that genetic material through these
17:44dang piluses okay all right so we have a
17:46basic understanding of that beautiful so
17:49we now know flagella we understand
17:51fembra we understand pyli
17:54the next thing that we talked about very
17:55briefly that we didn't say we had a
17:56structure to show you is called an
17:58endospore endospores are basically
18:01specialized structures that are only
18:03found in certain types of bacteria
18:06okay there's a you know there's a bunch
18:08of them but the big ones that i want you
18:10guys to know about the endospores is
18:12they're they're found
18:14in very particular type of bacteria i'm
18:17just going to say the claustridium
18:19species
18:20and there's different types of
18:22clostridium species clostridium tetani
18:25right the tetanus
18:27clostridium perfringens
18:30uh there's
18:31again there's also clostridium difficile
18:34c diff so those types of bacteria
18:37have the ability to produce something
18:39called endospores another one is called
18:43bacillus
18:45anthracis
18:49so these bacteria
18:52have the ability to produce these really
18:54nasty things
18:55called
18:56endospores
18:57now what the heck are these endospores
19:00why are they produced why are they so
19:01nasty and why are they you know what's
19:04the significance of them within these
19:05particular bacteria
19:07so endospores
19:09basically
19:10are going to allow for bacteria to be
19:12resistant
19:14to very harsh environments
19:17so what do i mean let's write this down
19:19so that you guys know exactly like what
19:21i what i'm trying to tell you here so
19:23the whole purpose the function
19:27is it allows for the bacteria to be
19:29resistant
19:32to
19:33high temperature so if there's really
19:35high temperatures the endospore will
19:38help the bacteria to be able to thrive
19:39in high temperatures
19:41it may be able to thrive in like where
19:44there's lots of uv
19:46radiation
19:48maybe in environments where there's less
19:52nutrients
19:54or lots of chemicals
19:58or maybe even a really dry environment
20:00okay so basically the function of the
20:03endospore is to be able to still survive
20:05and become resistant
20:07to very harsh environments like high
20:09temperature lots of uv radiation lower
20:12nutrients maybe kind of a dry
20:14environment chemicals like antibiotics
20:17things of that nature
20:19so how does it do that is the question
20:21so again we know what type of bacteria
20:22this would form in we know the whole
20:24purpose of them is to function to become
20:26resistant in particular types of harsh
20:28environments now how does it do that but
20:30what happens here is you have this
20:32actual bacteria like the clostridium or
20:33the bacillus anthracus and it has this
20:36actual kind of like vegetative cell we
20:38call it inside of that vegetative cell
20:40you have your bacterial chromosome right
20:41which is basically the dna that's
20:43designed to be able to make enzymes and
20:44proteins that allow for the bacterial
20:46cell to function
20:47when it's exposed to these harsh
20:48environments high temperature lots of uv
20:50radiation certain types of chemicals or
20:53lower nutrient you know availability we
20:56needed to be able to you know
20:57accommodate and acclimate to that so
20:59what does it do first thing it does is
21:01it undergoes kind of replication process
21:03so we take that actual bacterial
21:04chromosome and we replicate it and so
21:06now we have two of these dnas right so
21:08we have some daughter dna
21:10then what we're going to do is is we're
21:12going to try to have this actual
21:14replicated dna kind of start like
21:16separating from one another and have
21:18them go to one end pole okay so we're
21:20going to have one of this actual
21:22daughter dna kind of congregate towards
21:24this end poll and have that mother
21:27bacterial dna kind of congregate to the
21:29other end pole
21:30once it does that and we kind of get
21:32them towards the impulse a cell membrane
21:35kind of partition or septa will form
21:38between the mother dna and this kind of
21:41daughter dna okay so now we form like a
21:43septa and technically this end here
21:45where we have that daughter dna we call
21:48that the four
21:50spore all right
21:52then what happens is something very
21:53interesting happens
21:56the actual membrane that's surrounding
21:58this mother dna wants to actually come
22:01around and kind of engulf or invaginate
22:05around
22:06the dna the daughter dna within the
22:07forespore and so it does that it
22:09actually kind of engulfs it and when it
22:11does that it forms like a double layered
22:13membrane
22:15around it so this actual kind of like
22:16mother cell component with the mother
22:18dna will kind of engulf and invaginate
22:21and wrap around that actual forespore
22:23portion and form a double layered
22:25membrane
22:26around that actual daughter dna then
22:28what happens is the mother dna starts to
22:30degrade by particular types of enzymes
22:32that'll get broken down okay then what
22:35happens
22:36now after we've formed
22:38that double layered membrane
22:40we actually want to put some particular
22:42types of sugar and
22:45protein content in between it and so
22:48then what happens is you put what's
22:49called a peptidoglycan layer
22:52between that double layered membrane
22:54okay so now we have a peptidoglycan
22:56layer there between the double layered
22:58membrane that's wrapped around the
23:00daughter dna that got invaginated by the
23:02actual or engulfed i should say by the
23:05mother cell component where the mother
23:07dna was and that got broken down
23:09then what happens is
23:12we actually take
23:13and have calcium kind of rush in
23:17to this endospore component so again
23:20it's going to have the peptidoglycan
23:21component in between that double layered
23:23membrane where their daughter dna is and
23:25there's going to be production of
23:26enzymes and proteins in that component
23:28of the endospore
23:30but what's going to happen now is we're
23:31going to have calcium
23:34kind of like rushing in we're gonna have
23:36calcium rushing in
23:38to this actual endospore now when
23:40calcium rushes in
23:42water
23:44starts leaking out
23:47kind of making it a little bit more of a
23:48drier environment in that area
23:51then
23:52after calcium rushes into the endospore
23:54we kind of pull water out of it what's
23:57the last thing that kind of happens here
23:59well it's kind of again recap here we
24:00have our double air membrane
24:03our double layered membrane contains
24:04within it what
24:06peptidoglycan layer
24:08the peptidoglycan layer
24:11then what happens you have calcium that
24:14rushes into the endospore which draws
24:15out water kind of drying out the
24:17endospore a little bit and then the last
24:19thing to happen is you want to put one
24:21more coating around this actual
24:23endospore that makes it again more
24:25resistant to harsher environments and so
24:28you put this kind of what's called a
24:29keratin coating this is called keratin
24:32coating
24:33around that actual spore and then lytic
24:36enzymes will actually break down
24:39the actual
24:41vegetative cell and release out that
24:44endospore that now can survive and
24:46thrive within these harsh environments
24:48because what does it have within it
24:50it has the dna that can make proteins
24:52and enzymes that allows for it to be
24:53able to function and then it has a
24:55peptidoglycan layer it has a dried out
24:57environment as a keratin coating
24:58everything that it needs
25:00to be able to really be able to be
25:02resistant
25:03in these all of these tough harsh
25:05environments which is pretty cool
25:07okay so that's something to think about
25:08okay we done nailed the appendages the
25:11specialized structures now let's go
25:14ahead and hit that cell envelope and the
25:15different components and functions there
25:17all right the next components we covered
25:18the appendages we covered the
25:19specialized structure of the endospore
25:21we know their structure we know their
25:23function we know the differences the
25:25next part is the cell envelope and this
25:27is really probably one of the more more
25:28important parts of this lecture is the
25:30cell envelope now the cell envelope i
25:32told you it was this big thick blue
25:34covering that we saw on this structure
25:36but in reality it's multiple different
25:38layers within that
25:40so what i want us to do is actually go
25:42through the layers of the cell envelope
25:44from the most outer part all the way to
25:47the most inner part systematically going
25:49through what is it made up of what does
25:51it do what's the significance of it
25:54so the first one which is the most outer
25:56component of the cell envelope is
25:58actually called there's two components
25:59it's actually the capsule or the slime
26:01layer they're relatively we kind of can
26:04put them in a category of what we call
26:06like the glycocalyx but
26:08let's kind of have a basic understanding
26:09of what the differences between these
26:11two are what's the significance of them
26:13the first one let's talk about is the
26:15capsule the capsule is actually made up
26:17of you see this green structure here
26:19it's actually made up of polysaccharides
26:21right but the polysaccharide layer here
26:24is really organized
26:26so what i want you to remember is a very
26:28organized polysaccharide coating that
26:31makes up that capsule when it's there
26:34okay so again organized polysaccharide
26:37network that is present within the
26:39capsule
26:41when you compare that to the slime layer
26:45the polysaccharide layering or network
26:48that's present here is a little bit more
26:51loose so let's actually kind of utilize
26:53those as kind of easy terms to help us
26:55to differentiate between capsule and
26:57slime layer it's a polysaccharide
26:59network organized in the capsule
27:01looser kind of a little bit more relaxed
27:04when it comes to the slime layer okay
27:06that's the basic concept
27:08what is the actual significance of the
27:11capsule and what is the significance or
27:13function of the slime layer the
27:15significance of the capsule is it
27:17actually acts as what's called a
27:19virulence factor so it acts as what's
27:21called a virulence factor you're like
27:23what the what did that mean man i got
27:26you dog the virulence factor
27:28is is it's basically the ability to
27:31promote infection okay so it has the
27:33ability to evade
27:35the immune system now how it do that
27:38what happens is the bacterial capsule
27:42makes it more difficult for certain
27:45types of white blood cells to
27:47phagocytose that bacteria so it actually
27:51decreases the phagocytosis
27:54kind of like efficacy if you will
27:57by white blood cells like macrophages
27:59and neutrophils and so it makes it
28:01harder for those white blood cells to be
28:03able to kind of latch on grab the
28:04bacteria and pull it in okay so that's
28:07one of the interesting thing about the
28:09capsules
28:10what i really really want you to know
28:12when it comes to significance in
28:13clinical medicine is that these capsules
28:16on bacteria can make them a little bit
28:18more
28:19nasty and cause some pretty nasty
28:21infections in certain populations and
28:23that's why we actually try to develop
28:24vaccines for some of these encapsulated
28:27bacteria that you guys should be getting
28:29you know what's the big ones that i want
28:31you to remember that we have vaccines
28:33for
28:34is what's called streptococcus
28:37pneumonia
28:38haemophilus influenza
28:41particularly type
28:43b and then what's called neseria
28:47meningitidis
28:49okay
28:50these are the three types of bacteria
28:53that have a capsule around them that we
28:55actually have vaccines for and are very
28:58important you know why these are very
29:00important because you know pertinent
29:01certain people who have like what don't
29:03have a spleen or they get their spleen
29:04removed for some particular reason maybe
29:05sickle cell anemia or
29:07you know hereditary spherocytosis some
29:08some kind
29:10if they don't have a spleen they're more
29:11susceptible to infections by
29:13encapsulated bacteria because the spleen
29:14is really good at removing those types
29:16of bacteria so again remember these
29:18bacteria that have capsules they're a
29:21little bit easier to evade the immune
29:22system by reducing that phagocytosis
29:24efficacy but we have vaccines to try to
29:27reduce that process there's other
29:29bacteria that have capsules that you
29:30know like you know pseudomonas e coli
29:32klebsiella salmonella but again these
29:34are big three that i want you to
29:35remember because these are the ones that
29:36we try to have vaccines for
29:38okay
29:39good slime layer we know it's a loose
29:40polysaccharide network what the heck is
29:42the significance of it
29:44the slime layer basically its function
29:47is to allow
29:49adherence
29:53to cell surface
29:56okay so it may be able to kind of like
29:57latch onto different types of cell
29:59surfaces within a host cell
30:01but what's even more interesting
30:03is
30:04it may be able to
30:06adhere to foreign
30:11substances
30:12foreign foreign substances or certain
30:14types of molecules so let me give you an
30:17example of that
30:19you know whenever somebody gets
30:20intubated and they put an endotracheal
30:22tube in it maybe it sits in there for a
30:23while because they have to remain
30:25intubated that endotracheal tube is a
30:27foreign substance and certain types of
30:29bacteria you know pseudomonas is a very
30:31classic example of this one so
30:33pseudomonas
30:36is a very classical example of a
30:38bacteria that loves to form slime layers
30:41if someone has like an endotracheal tube
30:44sometimes the pseudomonas bacteria can
30:46actually adhere to the endotracheal tube
30:48and form kind of a biofilm
30:50around and increase the risk of you know
30:52ventilator-associated pneumonias
30:54if you have a catheter that's placed
30:56into a vein like a central venous
30:58catheter
30:59okay a central venous catheter there's
31:01also a risk of bacteria kind of clinging
31:03on to that foreign catheter substance
31:05and leading to slime layers and biofilms
31:07forming on that and then lastly if
31:09there's kind of like a foley catheter
31:12or urethra catheter again that's a
31:13foreign substance that certain types of
31:15bacteria like pseudomonas may cling to
31:16and form biofilms around
31:18so that's kind of the big thing to
31:20remember when it comes to the actual
31:22slime layer
31:24now we covered that aspect we have the
31:25capsule we have the slime layer we know
31:27their differences in structure we know
31:28their function we know the significance
31:30of them let's move on to the next aspect
31:32and the next inner part of the cell
31:34envelope which is the outer membrane
31:36alright so we covered the capsule we
31:38covered the slime layer let's go to the
31:39next inner layer which is the outer
31:41membrane now outer membrane what is it
31:43made up of it's basically a phospho
31:48lipid
31:50bilayer
31:52but it has a very very specific type of
31:55structure and components within it which
31:57we'll annotate here in just a second
31:58what i do want you to really really
32:00really don't forget
32:02the outer membrane is only present in a
32:05particular type of bacteria
32:08it is only
32:11in gram-negative bacteria please don't
32:13forget that okay
32:15outer membrane only present in gram
32:16negative bacteria it's a phospholipid
32:18bilayer now let's talk about what is in
32:20that phospholipid bilayer that makes it
32:22so significant
32:23so we're going to take a gram negative
32:25bacteria parts of that actual outer
32:28membrane and zoom in on it when we do
32:30that we get this structure so obviously
32:31you can see your phospholipid bilayer
32:33here you can see
32:35the uh you know the glycerol head and
32:37you can see well the phospholipids and
32:38then you can see the fatty acid tails
32:40here
32:41some of the actual structures that are
32:42present in this outer membrane
32:45you have like porins right so these are
32:47basically just kind of like little
32:48proteins that allow for the transport of
32:50certain types of drugs or substrates or
32:53certain types of molecules to be able to
32:54transport in and out of the bacterial
32:57cell simple right but what's really
32:59important
33:01is that there is a endotoxin
33:04write that down
33:05this is a
33:07in do
33:09toxin that is present within this outer
33:11membrane and we're going to abbreviate
33:14this we call this lipopolysaccharides
33:17lipopolysaccharide lps
33:19the lipopolysaccharide is an endotoxin
33:22we'll talk about the significance of a
33:23second but we have to know what are the
33:24three components of the life of
33:26polysaccharide and which component of
33:28that lipopolysaccharide is actually the
33:30scary negative one
33:32three parts of it you have this red part
33:35this red part here is called lipid
33:39a
33:40okay and this is the nasty one and we'll
33:42talk about what why it's nasty in a
33:44second
33:45the next one is the pink part
33:47so we call this we're gonna call this
33:49the core
33:52polysaccharide
33:54okay
33:55so basically like a a
33:58polymer of sugar molecules
34:00and then this blue component which is
34:02extending out here
34:05okay
34:07this component here that's extending out
34:09is called the o
34:12antigen okay it's called the o antigen
34:15these three components make up the
34:17endotoxin the lipopolysaccharide
34:20now why is this significant the lipid a
34:23is actually the one that can activate or
34:26stimulate
34:28particular types of white blood cells
34:30you know like macrophages
34:32it can stimulate macrophages to release
34:34particular types of cytokines like
34:36interleukin-1
34:37interleukin-6
34:39tumor necrotic factor alpha and
34:41basically what these things can do is
34:43they can cause tons and tons and tons of
34:44problems they basically can potentially
34:47stimulate kind of a septic process
34:50because they can cause fevers they can
34:52cause a massive inflammatory reaction
34:54they can cause blood clots that lead to
34:56dic they can cause damage to the
34:57endothelium they can cause vasodilation
34:59and hypotension tons and tons of
35:01problems
35:03the core polysaccharide nothing
35:05particular to know about that
35:07but the o antigen whenever our immune
35:10system becomes activated they get
35:12exposed to this bacteria and they start
35:14to basically amount an immune response
35:16and produce antibodies you know where
35:18the antibodies love to attack
35:20they love to attack that o antigen so
35:22you want to remember that that is an
35:23antibody kind of attachment site on the
35:26actual bacteria so what i want you to
35:28remember is that antibodies
35:33attack
35:34or attach to the o antigen of the actual
35:38lipopolysaccharides
35:40okay beautiful that is the outer
35:42membrane what i want you to know
35:43phospholipid bilayer has porins has
35:45lipopolysaccharide structure which is an
35:46endotoxin three components of it lipid a
35:49core polysaccharide o antigen o antigen
35:52is a site for antibody attachment when
35:54the immune system is activated core
35:56polysaccharide nothing particular lipid
35:58a is the nasty component which has the
36:00ability to stimulate macrophages immune
36:03system cells to release massive amounts
36:04of cytokines particularly these three
36:06which can induce a septic vasodilatory
36:09process
36:10okay
36:11and big thing remember this is only in
36:14gram negative bacteria okay cool we
36:17covered the most outer layer capsule
36:18slime layer we covered the next one
36:20which is only gram negative bacteria
36:21which is the outer membrane what's the
36:23next part the next one which is just
36:25inside of the outer membrane is the cell
36:27wall all right so the next component is
36:29the cell wall so again we're going from
36:30outer to inner we got that capsule slime
36:32layer we got then the outer membrane
36:34cell wall
36:35cell wall one of the big things that i
36:37want you guys to know before we go over
36:38like what it's made up of
36:40because that's kind of a big topic
36:42is what is the kind of big function of
36:44it okay so we're kind of going a little
36:45bit backwards we've been talking about
36:46structure then function but just real
36:47quickly let's kind of reverse it on this
36:49one what's function and then we'll talk
36:50a little bit more about structure
36:52so function of the cell wall is
36:53obviously it gives shape to the bacteria
36:56it helps with kind of the structural
36:57integrity of the bacteria
37:00so when i talk about that it's involved
37:03with shape
37:05and integrity
37:09of bacteria
37:10okay
37:12kind of resistance against like osmotic
37:14kind of changes as well
37:16but one of the things is that's big with
37:18this and we'll have another video
37:19dedicated to kind of like bacterial
37:20nomenclature is it gives bacteria
37:24different shapes which is really cool so
37:26for example you can have a bacteria
37:27that's like circular like cocci or it's
37:29rod shaped like bacillus or it's kind of
37:31a mixture of coccy and basil so it's
37:32coxal bacillus you can have one that's
37:34kind of like comma shape which is like
37:36your vibrio
37:37and then you have the ones that are kind
37:39of like snake or kind of like spirally
37:40shaped we call spirilla and so we'll
37:42have a kind of a another video
37:44particularly focusing on bacterial
37:45nomenclature and things like that but i
37:47think it's one of the cool things about
37:48the cell walls it gives that shape which
37:50we have different types of nomenclature
37:51for which is pretty cool
37:53the other thing that i want you guys
37:54know about the cell wall is that this is
37:56present in both gram-positive and
37:59gram-negative bacteria so it's in both
38:04gram-positive
38:06and negative bacteria
38:08but we'll talk about in just a second
38:10there is a difference in the cell wall
38:13particularly the thickness of the cell
38:15wall when you're comparing it from grand
38:16positive to gram negative we'll talk
38:17about in a little bit
38:19so we know that it's involved in shape
38:21integrity you know resistance against
38:22osmotic changes
38:24and it's in both gram-positive
38:26gram-negative bacteria the next thing
38:27that i want you guys to know is actually
38:28like what is it made up of like some of
38:30the structure component of it and it's
38:32actually made of what's called a peptido
38:36glycan
38:38peptidoglycans you're like what the heck
38:40would that mean man
38:42so peptidoglycans
38:44there's two components in that in the
38:46name peptido so there's proteins
38:48peptides and glycans sugar
38:51so let's focus on the sugar portion the
38:53glycan there's two components that we
38:55actually polymerize and make these
38:56glycan backbones
38:58and this one here in pink we're going to
38:59call i'm just picking
39:01there's no particular reason i'm just no
39:02rhyme reason just picking it the pink
39:04one we're going to call in acetyl
39:06muramic acid which we call nam that's
39:09one of the actual sugar molecules and
39:11the other one here in this kind of blue
39:13color here
39:15is called in acetyl glucosamine which
39:18we're going to just abbreviate as nag
39:20what happens is these nags enamels get
39:23polymerized together and when they do
39:26that they make this glycan or sugar
39:28backbone
39:29then what happens is there's a special
39:32type of enzyme called a transpeptidase
39:35which is kind of a
39:36domain on a special type of enzyme we'll
39:38talk about later called a penicillin
39:39binding protein and what that protein
39:42does is is it kind of links together
39:46these
39:48glycan backbones so this is your peptide
39:51chains which are going to be linking the
39:53glycan backbones together so that's what
39:55i want you to remember is when we talk
39:57about the peptidoglycan layer of the
39:58cell wall it's made up of nags and names
40:01that are polymerized to make a glycan
40:03backbone and peptide chains that are
40:06formed by a very specific enzyme which
40:08is called the transpeptidase which is a
40:10domain on the penicillin binding
40:12proteins that cross link them together
40:15beautiful
40:17one of the big things though let's
40:19briefly talk about here is kind of like
40:23what is some of another significant
40:25point about this peptidoglycan layer
40:28well one of the big things i want you
40:29guys to remember is that there is
40:31another structure that's kind of like
40:33similar to the lipopolysaccharides
40:35remember the lps is the endotoxin only
40:38found in the outer membrane which is
40:40only found in gram-negative bacteria you
40:43know gram-positive bacteria they have
40:45something that's kind of like homologous
40:46to that
40:47and so in that
40:50they have a molecule called
40:53lipotocoic acid which we're going to
40:55abbreviate as lta
40:58lipoic acid is this purple structure
41:00that extends from the inner membrane and
41:03extends all the way through the cell
41:05wall
41:06what is the significance of the
41:07lipochoic acid that extends through the
41:09cell wall you know what it loves to do
41:12it loves to be able to stimulate white
41:14blood cells like macrophages and
41:17stimulate these macrophages to release
41:19particular types of cytokines like
41:20interleukin-1 interleukin-6 tumor
41:23chronic factor alpha which have the
41:25ability to produce fever hypotension
41:28increase inflammation vasodilatory
41:30effects and potentially kind of cause a
41:32septic process
41:33so that is your
41:34lipotocoic acid now your pile like well
41:37what is this pink thing that doesn't
41:38touch the inner membrane but it's still
41:40kind of incorporated within that cell
41:42wall or peptidoglycan layer glad you
41:44asked this thing here is not connected
41:47to the lipid membrane but it is a kind
41:50of like fatty acid structures we call
41:52this a tachoic
41:54acid
41:56okay
41:57tachoic acid so tachoic acid is a part
42:00of this structure that extends just
42:01through the cell wall doesn't touch the
42:03inner membrane light petrichoric acid
42:05touches the inner cell membrane extends
42:07through the cell wall and involved in
42:09stimulating this kind of interleukin one
42:11interleukin 6 tuna chronic factor alpha
42:13process
42:14last quick thing here just because i
42:16said that there was a small difference
42:18here in peptidoglycan layer what i want
42:20you to remember when it comes to gram
42:22positive versus gram negative gram
42:24positive
42:25versus gram negative with the
42:28peptidoglycan layer gram-positive has a
42:31thicker
42:33peptidoglycan layer and gram-negative
42:35bacteria has a thinner
42:39peptidoglycan layer please don't forget
42:41that
42:42okay so we have cell wall maintains
42:45structural integrity prevents like
42:46osmotic kind of changes
42:48and
42:49influences cell shape
42:52found in both gram-positive gram
42:53negative bacteria it's made up of
42:55peptidoglycans which is made up of
42:57n-acetylglucosamine and acetyl-muramic
42:59acid which is sugar molecules that are
43:01polymerized to make a glycant backbone
43:03cross-length through trans-peptides
43:05and again gram-positive has a thicker
43:07peptidoglycan layer gram-negative has a
43:09thinner peptidoglycan layer and again
43:11another significance is that only in oh
43:14i gotta make sure you guys remember this
43:16only in gram positive
43:20bacteria do they have this
43:23lipotocoic acid that is involved in this
43:25kind of interleukin-1 interleukin-6
43:27tumor chronic factor alpha process that
43:29can cause kind of a septic process it's
43:31kind of analogous to the lps that was in
43:33gram-negative bacteria so only
43:35gram-positive bacteria let's actually
43:37make this look a little bit nicer
43:38gram-positive bacteria
43:40has that lipotocoic acid
43:43all right beautiful roasted let's move
43:44on to the next component here which is
43:46the periplasm all right so the next part
43:48so again we've covered capsule slime
43:50layer from outer to the outer membrane
43:52to the cell wall to the periplasm now
43:56the periplasm is the next structure now
43:58here's the big thing the periplasm how
44:00do you define it
44:01it is the space between i'm going to
44:03abbreviate this the outer membrane which
44:06is only present in what type of bacteria
44:08okay negative bacteria
44:09and the inner membrane which we haven't
44:12gotten to yet but this is present in
44:13gram-positive and gram-negative bacteria
44:16it's that space between
44:18now what was in that space that we
44:19talked about if you guys remember outer
44:21membrane and gram-negative bacteria and
44:22then we hit cell wall so that's our
44:24peptidoglycan layer with the nam nag and
44:27trans-peptide uh bonds there
44:30compare the peptide bonds formed by the
44:31transpeptidases
44:33in the periplasmic space okay which is
44:36the space between the outer membrane and
44:37inner membrane which obviously which
44:39bacteria only have outer membranes
44:41gram-negative so you can only have a
44:42periplasmic space and
44:45gram-negative bacteria therefore by that
44:47definition
44:48what is the significance of it you see
44:50this little like dude
44:51little bee dude
44:53this is a very special enzyme and this
44:55enzyme we talked about a little bit over
44:56here before it's called a beta lactamase
45:00remember that when we talked about the
45:01pilus
45:03you can actually like have those
45:04plasmids that actually have genes that
45:05can be transcribed translated make
45:07proteins like beta-lactamase that make
45:08things resistant to antibiotics and you
45:10can pass that on to other bacteria
45:12to make them more resistant
45:13beta-lactamase sits within the
45:14periplasmic space so you know whenever
45:16somebody takes like for example they
45:18have a gram negative bacteria and then
45:19they take a drug like penicillin
45:22and penicillin has to get through the
45:24outer membrane through the peptidoglycan
45:25layer and what happens is this beta
45:28lactamase
45:29will come and say hey penicillin i'm
45:31going to inhibit you
45:32and then render it ineffective and being
45:34able to you know prevent or inhibit the
45:36cell wall growth so that's kind of the
45:38cool thing about the beta-lactamase so
45:40again periplasm only technically found
45:42in gram-negative bacteria since only
45:44gram-negative bacteria of outer membrane
45:45and inner membrane and the definition is
45:47the space between outer and inner
45:48membrane in that space is the
45:50beta-lactamase allowing for resistance
45:52to antibiotics like penicillin boom
45:54roasted move on to the last component of
45:56the cell envelope
45:58what is the most inner component the
46:00inner membrane baby
46:02inner membrane what is it made up of
46:04it is a phospho
46:08lipid bilayer
46:11now within that phospholipid bilayer
46:13there's obviously different types of
46:16proteins so different types of like
46:18porins
46:19there's different types of enzymes that
46:21are involved in like you know oxidative
46:23metabolism or different types of dna
46:26replication or other enzymatic metabolic
46:28processes
46:30but one of the big proteins that i need
46:32you guys to definitely remember is this
46:35one right here that's shaped like a p
46:39this right here this bugger
46:42is called the
46:44penicillin
46:46binding
46:49protein
46:51now the penicillin binding protein we
46:53talked about a little bit over here and
46:54we can actually kind of refer to it
46:55while we're here the penicillin binding
46:58protein has kind of like one like domain
47:00like a little like like imagine like a
47:02little arm out here
47:03that has what's called a trans
47:07peptidase
47:10function
47:12and what does that mean
47:14it means you see these bonds here that
47:16are formed the peptide bonds that are
47:18formed between the glycan backbones
47:20that's actually by that enzyme which is
47:22kind of a domain on the penicillin
47:24binding protein which is found where
47:26on the inner membrane inner membrane is
47:29that found on gram-positive bacteria
47:31gram negative bacteria or both
47:33well all of them have it right so both
47:35gram-positive
47:38and
47:39gram-negative bacteria have this inner
47:41membrane so they both have penicillin
47:43binding proteins
47:44the whole reason this is significant is
47:47when you give a drug
47:48like penicillin what does penicillin do
47:51penicillin's design is to be able to
47:54inhibit
47:56that transpeptidase portion on the
47:58penicillin binding protein
47:59if you inhibit this portion can you
48:02crosslink the actual glycan backbones
48:04that stabilize the cell wall no if you
48:07can't stabilize that cell wall are you
48:08going to be able to grow it no you'll
48:10start losing the structural integrity
48:12you'll start losing the ability to
48:14resist against osmotic fluctuations and
48:16then what happens the actual bacteria
48:18can die
48:19and so that's one of the big things to
48:20think about is the significance of this
48:23penicillin binding protein
48:25okay boom roasted baby we done did it
48:28that is the cell envelope now the
48:30absolute most important thing to take
48:33away from this is you guys are probably
48:34going to get a question on the exam
48:36about what are the differences in the
48:38cell envelope between gram-positive and
48:40gram-negative bacteria let's quickly and
48:42i mean quickly review what we have just
48:44talked about this entire time
48:47here's your gram positive bacteria
48:48here's your gram negative bacteria
48:50from outer to inner they both can have
48:53what
48:54a capsule or a slime layer
48:57then you go to next thing okay what's
48:58the next thing that we hit we said outer
49:00membrane outer membrane is only present
49:02in gram-negative bacteria not present
49:04here in gram-positive bacteria what's on
49:07the outer membrane that was so
49:09significant and important we said it's a
49:11phospholipid bile that had porons that
49:12allowed for things to move in and out
49:14but the big thing was this thing
49:15sticking out here called the lps the
49:17endotoxin called the lipopolysaccharides
49:20you don't see that on gram-positive
49:21bacteria but you do see that on
49:23gram-negative bacteria okay what's the
49:25next thing after the outer membrane then
49:27we had cell wall
49:28cell wall is the
49:30peptidoglycan component which is made up
49:32of
49:33nags which is your glycan backbones and
49:35your peptide bonds which are cross
49:36linking them so here's your
49:38peptidoglycan layer here which is
49:40component of the cell wall and then here
49:42in the gram-negative bacteria what do
49:44you notice in the difference of
49:45thickness here
49:47gram-positive they got a thick
49:49peptidoglycan layer and then in the
49:51gram-negative they got a baby thin
49:53peptidoglycan layer so that's another
49:54big significant point here
49:57the other thing here that's important
49:59is that in that cell wall in
50:02gram-positive bacteria they have this
50:04structure that extends from the actual
50:05inner membrane or from the cell wall
50:08only in gram-positive bacteria what is
50:10this thing here called the lipotechoic
50:13acid or tochoic acid do you see that
50:15here in the gram-negative bacteria no so
50:17there's no lypotech acid or techoic acid
50:19present in the gram-negative bacteria
50:22the next thing is we had a periplasmic
50:24space do you see a periplasmic space
50:26here in gram positive no because they
50:27don't have an outer membrane
50:29it's the space between outer membrane
50:30and inner membrane which one has the
50:32outer membrane gram-negative bacteria so
50:34it has to be the space between here
50:36what's in that space oh a little
50:37beta-lactamase enzyme
50:39and that's only in gram-negative
50:41bacteria
50:42and then the last thing here is that you
50:44have the gram-positive bacteria and
50:45gram-negative bacteria they both have
50:47the inner membrane and they both have
50:48the penicillin-binding proteins and
50:50remember the last thing i told you guys
50:52they both can have flagella but which
50:54one did i tell you that the pilots is
50:55primarily most common in
50:57gram-negative bacteria and what was this
50:59example that we used as gram-negative
51:01bacteria being able to transmit kind of
51:03resistance to antibiotics the
51:04beta-lactamase which one has
51:05beetalectomies
51:07gram negative bacteria does it have a
51:08hearing ground positive no so we now
51:11understand and we have a pretty good
51:12understanding of gram-positive versus
51:13gram-negative bacteria now we have to do
51:15to just cap it all off is talk about the
51:17actual protocol procedures that you need
51:19to understand to do in the lab about how
51:22to do the gram staining procedure and
51:24microscopically visualize what is the
51:27difference between gram positive and
51:28gram-negative bacteria let's hit that
51:30all right so now what we have to talk
51:32about is the gram-staining procedure you
51:33guys need to know this because when you
51:34guys are in the lab you'll have to know
51:36the steps to be able to perform in order
51:39in sequence why you're doing it in this
51:40particular sequence and then after you
51:43know how to do this procedure step by
51:45step you should be able to identify
51:47microscopically which one is
51:49gram-positive and which one's
51:50gram-negative bacteria based upon the
51:52staining or the color of it and then
51:53which ones kind of fall into this you
51:55know atypical
51:57category of bacteria knowing which one
51:58those are
52:00all right so let's go through this
52:01process you take you grow your bacteria
52:02in whatever culture you've done it
52:04you take that you scoop it onto a slide
52:07after you've applied the bacteria onto
52:09the slide which is your step one you're
52:11then going to take and heat up the slide
52:14when you heat up the slide the whole
52:15purpose of that is to get the bacteria
52:17to fixate to the slide okay so the
52:19second step is to heat up the slide to
52:20get the bacteria to fixate
52:23once the bacteria has been fixated to
52:24the slide the third step is you're going
52:26to apply what's called a particular type
52:28of stain called a crystal violet stain
52:30which obviously gives off a violet
52:32purplish type of color you apply the
52:34stain to the slide
52:36what happens is the bacteria that are on
52:38the slide should suck up that crystal
52:41violet into the peptidoglycan layer
52:44and they should stain purple which the
52:47bacteria have peptidoglycan layers both
52:49gram-positive and both gram-negative
52:51bacteria so let's imagine for a second
52:53you looked underneath
52:56you looked at the microscope you pulled
52:57it after you've applied the the crystal
52:58bile you looked in the microscope and
53:00you looked to see what the bacteria look
53:01like all of them should stain purple
53:03because they've taken up that crystal
53:06violet color why is that let me explain
53:08this for a second here
53:09if you look here we have on this side
53:12our gram positive and here we have our
53:15gram negative bacteria
53:17you give the crystal violet now the
53:19crystal violet is just going to get
53:21soaked up into the peptidoglycan layer
53:23now the gram positive has a very thick
53:26peptidoglycan layer so it has lots of
53:28area that you can have that actual
53:30crystal violet soak up into
53:33okay also here's another interesting
53:35thing
53:36gram-negative bacteria have an outer
53:38membrane which makes it a little bit
53:39more like selectively permeable so less
53:42crystal violet will be able to get into
53:44the peptidoglycan layer because it's
53:46going to have to go through that porins
53:47so less of it will get in there and
53:49another additional fact here is that
53:51there's less peptidoglycan so there's
53:53less actual like amounts of crystal
53:55violet that's going to be within that
53:57peptidoglycan layer but nonetheless
53:59there's peptidoglycan that's saturated
54:02within this actual there's crystal
54:04violet sorry stain that's saturated
54:06within this peptidoglycan layer of both
54:08gram positive
54:09and gram-negative bacteria
54:11okay
54:13the next step after we've applied the
54:14crystal violet is we don't want that
54:16crystal violet to kind of like
54:18leech out
54:19and so how do we kind of like
54:21cement or keep that crystal violet kind
54:24of like fixated and stuck in that area
54:26of the peptidoglycan component of the
54:28grand positive and negative bacteria
54:30we apply a mordant
54:33and this mordant that we're going to
54:35have here in this
54:36reddish color here
54:38is going to be called iodine
54:41it's called a mordant
54:44and all that means is
54:47let's say here we have again our gram
54:50positive bacteria our gram negative
54:53bacteria and we can identify that based
54:54upon thick bipedal glycogen thin
54:56peptidoglycan and gram negative only has
54:58the outer membrane gram positive does
55:00not right
55:01we know that the crystal violet in step
55:04three here has been saturated
55:06in that actual peptidoglycan layer
55:09we know it's also saturated here within
55:11that gram-negative layer what the iodine
55:14does is it kind of latches onto the
55:16crystal violet and keeps it really kind
55:18of like locked into that peptidoglycan
55:20layer so it kind of acts like a little
55:22bit of a cement to keep some of that
55:24crystal violet in the peptidoglycan
55:27layer okay
55:29so that's our fourth step
55:31now
55:32the fifth step is the interesting step
55:36the fifth step is we apply something
55:38called like ethanol or alcohol some kind
55:41of alcohol-based substance maybe even
55:43like acetone sometimes is applied
55:46but it's an ethanol wash right
55:48and what you do is you take like a
55:50bottle of like you know some ethanol or
55:51acetone and you keeps you know you
55:53squirt that over for a certain period of
55:55time over the slide and you're trying to
55:58wash some of the crystal violet
56:01out of the peptidoglycan layer
56:03now
56:05the theory behind how this actual like
56:07ethanol does this is it may compress
56:09the actual peptidoglycan layer and also
56:12may have like a little bit of a
56:13dissolving effect or put holes within
56:15kind of like phospholipid bilayers
56:18to allow for some of that crystal violet
56:19to be able to leech out
56:21but either way the whole design of the
56:23ethanol is to kind of suck some of the
56:25crystal violet or wash some of the
56:26crystal violet out of the peptidoglycan
56:29layer now
56:31come here for a second and realize what
56:33do we have so far going back to this
56:34point here again here is our
56:37gram positive here's our gram-negative
56:39bacteria we have that peptidoglycan
56:42layer filled with our crystal violet
56:44here and that gram positive we have it
56:46filled here within the gram negative we
56:49have the mordant trying to kind of keep
56:51it situated in here which is the iodine
56:54and then we apply the ethanol
56:56when you apply the ethanol
56:59it is going to pull
57:01some of that crystal violet out of the
57:03grand positive bacteria it's going to
57:04pull some of it out but it shouldn't
57:05pull ton as much out as you as you
57:08actually think the reason why is why
57:11you have saturated that peptidoglycan
57:13layer with tons of crystal violet
57:15there's tons of it and then you have
57:17some of it pretty fixated really well in
57:18there with the iodine as the mordant
57:21the gram negative bacteria though there
57:23wasn't really much
57:25crystal violet in there to begin with
57:27because you had a very thin
57:28peptidoglycan layer there's not a
57:30crystal violet there present in general
57:31like a mount and also there was less of
57:34that crystal violet probably able to get
57:36in
57:37to the actual peptidoglycan layer
57:39because of the outer membrane so when
57:40you apply ethanol to the gram negative
57:43bacteria it's going to wash out the very
57:45little amounts of crystal violet that
57:47you do have you're going to have lots of
57:48crystal vitamin gram positive not as
57:50much in gram negative so when you apply
57:52that ethanol wash
57:53it is going to suck out tons and tons of
57:56that crystal violet that you had there
57:58and so effectively what should happen is
58:00if you took at that moment
58:03looked at the slide after you applied
58:05the ethanol wash what should happen
58:08the bacteria that were gram positive
58:11should still be retaining that crystal
58:13violet unless you freaking applied so
58:16much ethanol that you literally washed
58:17all of it out so sometimes if you do
58:18apply too much ethanol for too long
58:20period of time you can leech out enough
58:22crystal violet out of the grand positive
58:24bacteria and it won't stain purple
58:25that's why you have to do it for you
58:27know you don't do it very long but once
58:29you
58:29have that ethanol wash and you look
58:31under the microscope the gram-positive
58:32bacteria should still be retaining some
58:34of that crystal violet so what color
58:35should they be under the microscope
58:37purple
58:38the gram negative bacteria in theory if
58:41you apply the ethanol wash and yank some
58:43of that crystal violet out the very
58:45little crystallite that you had there
58:47there shouldn't really be any purple
58:49color there so they shouldn't have any
58:51purple color they shouldn't stain purple
58:54and that will be your gram negative
58:55bacteria but we still can't identify
58:57them because they're not staining a
58:59particular color that makes them obvious
59:00on the slide
59:01so how can we make it obvious
59:04that that the ones that aren't actually
59:06staining it there is some gram negative
59:08bacteria on that slide how do i identify
59:10them because i don't have a color that
59:11makes them pop or stand out
59:14well that's where the next thing comes
59:15in
59:16the next thing is we apply what's called
59:17a counter stain
59:19the counter stain is we use something
59:21which is this purple structure we apply
59:23what's called the counter stain
59:26we apply this molecule called safranin
59:30what safranin does is is it should soak
59:33into the peptidoglycan layer that
59:35doesn't have any crystal violet so
59:37wherever there's no crystal violet that
59:39saffron should soak into that
59:40peptidoglycan layer let's think here
59:42here's our
59:44gram positive bacteria here's our
59:47gram-negative bacteria
59:50we said that some of the
59:52crystal violet may get washed
59:54from the gram-positive bacteria but
59:56there should be still a decent amount
59:57that's actually retained there keeping
59:59it purple
1:00:00you washed out the crystal violet
1:00:02whenever you did the ethanol wash from
1:00:04the gram-negative bacteria but
1:00:06if you give that saffron in that should
1:00:09soak up
1:00:10into the peptidoglycan layer that does
1:00:12not have any crystal violet it should do
1:00:14what
1:00:15give the color of that stain when you
1:00:17look at it under the microscope
1:00:20so if i look at it under the microscope
1:00:23now the gram
1:00:24negative bacteria that didn't weren't
1:00:26staining previously should stain
1:00:28pink why because they soaked up that
1:00:31safranin
1:00:32and that will tell me what type of
1:00:35bacteria i have so at the end of it
1:00:37after you've applied your counter stain
1:00:39or your saffron and you look under the
1:00:40microscope the bacteria that stain pink
1:00:43mean that they retained the actual
1:00:45counter stain or the safranin has to be
1:00:48the gram-negative
1:00:50bacteria
1:00:52and then the ones that retained the
1:00:54actual crystal vial throughout the
1:00:55entire time
1:00:56is the
1:00:57gram-positive
1:00:59bacteria
1:01:02i hope that makes sense
1:01:03okay
1:01:05the last thing is that sometimes
1:01:08there's bacteria
1:01:10that don't really stain like an obvious
1:01:12color
1:01:13and so we kind of fit them into this
1:01:15weird like they're kind of considered
1:01:16gram-negative bacteria
1:01:19but they don't really stain and so we
1:01:21actually call them atypical bacteria all
1:01:24i want you to know is the names of these
1:01:26atypical bacteria and that's it all
1:01:28right so again what i really want you to
1:01:29remember is that these atypical bacteria
1:01:31are technically clumped within the
1:01:33category of gram-negative bacteria
1:01:35because they don't stain a particular
1:01:36grit like crystal violet color they
1:01:38don't really stain in general
1:01:39but these atypical bacteria you should
1:01:41actually remember them because again
1:01:43they're not really going to have that
1:01:44classic gram-positive gram-negative
1:01:46stain
1:01:47and so there's a mnemonic that helps us
1:01:50to be able to remember this it's these
1:01:52atypical microbes usually lack color
1:01:55because microbes barely eat ramen
1:01:58okay it's a random one but it it may
1:02:01help you to remember it so the t in
1:02:04these stands for trypanema
1:02:06so
1:02:07trypanemapolitum right which is the
1:02:09bacteria that causes syphilis the a for
1:02:12atypical stands for ana
1:02:15plasmosis
1:02:18the m in microbes can be micro
1:02:22plasma
1:02:24the u and usually is for urea
1:02:28plasma
1:02:29and let's move on over here to these the
1:02:31l in lac is for leptospira
1:02:36and it can actually be a double you can
1:02:38actually consider it legionella
1:02:41the c in color
1:02:43would be for chlamydia
1:02:48the b and because can be for bartonella
1:02:54the m in microbes is there so there's
1:02:56another m this was mycoplasma this is
1:02:58mycobacteria
1:03:04the b and barely there's another b this
1:03:06was for bartonella that because the
1:03:07barely can be borrelia
1:03:10like the berelia bergdorferi and lime's
1:03:12disease
1:03:13the e for eat is erlichia
1:03:17like erlichiosis
1:03:19from the tick bite and r is for ramen
1:03:23which is rickettsia
1:03:25which again is another kind of species
1:03:27of ticks okay bacteria from ticks so
1:03:30again this would cover
1:03:32your atypical bacteria again
1:03:36quick reminder of these these are
1:03:37technically within that gram-negative
1:03:39category they don't really fit in that
1:03:42actual staining process of purple or
1:03:44crystal via i'm sorry crystal violet or
1:03:46that pink kind of saffron in color and
1:03:48again it's trypanema anaplasmosis
1:03:50mycoplasma urea plasma leptospira or
1:03:53lesionella chlamydia bartonella
1:03:55mycobacteria borrelia erlichia and
1:03:59rickettsia that covers our discussion on
1:04:02the structure and function of bacteria
1:04:05all right ninja nerds in this video we
1:04:07talk about the structure and function of
1:04:08bacteria as well as the gram staining
1:04:10procedure i hope it made sense i hope
1:04:12that you guys enjoyed it i hope you
1:04:13learned a lot as always ninja nerds
1:04:15until next time
1:04:20[Music]
1:04:36you

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