Bacteria | Structure and Function

what's up ninja nerds in this video

we're going to be talking about the

structure and function of bacteria

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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