Hi. It's Mr. Andersen and in this podcast I'm going to talk about these
guys, bacteria. Here's a couple of e. coli that are undergoing binary fission. Bacteria
is an ancient domain. They're quite a bit different than us. We're in the domain eukarya.
But they're just as fascinating. They've been around billions of years. Some of them are
evil to us. And some of them are beneficial to us. And so if you look at their phylogeny,
basically if this is that last universal common ancestor, or LUCA, basically they diverge
from us a long time ago. And we have all these different types of bacteria. Know this though.
That there was horizontal gene transfer as well. So mitochondria, chloroplasts inside
our cells used to be bacteria of their own. And so they went like this. And became part
of our cells. And so there's a ton of this horizontal transfer. But basically bacteria
is going to be this other group. And they're going to be diverse. And they fill all of
these different niches on our planet. We're more related archaea bacteria and I'll talk
more about that is the next podcast. Let's talk about the structure of them. First thing
would be the size. Imagine this right here. This bacteria under a computer screen is about
this big. Then eukaryotic cells are going to be about the size of you. So we're like
10 times bigger than a prokaryotic cell. Or a bacterial cell. A few other things that
are different. Well, our DNA is going to be organized in chromosomes which are linear
stretches. And they're going to be inside a nucleus. And so inside a bacteria they have
what's called a nucleoid region. So all of their genetic information is going to be in
here in this wadded up center location inside the bacteria. But they'll also have extra
bits of DNA. And those are going to be found in these structures called plasmids. They're
genetic material instead of being in a line is actually going to be in a loop. And so
they're going to have a loop of DNA. Another thing they don't have are going to be introns.
In other words every little bit of this DNA is going to code for genes or is going to
have a function. And then they're going to have these plasmids which are little extra
bits of DNA. But the whole thing is wound up so it fits inside the bacteria. Another
thing that they're going to have is let me kind of jump ahead, as we move out is going
to be the cell wall. And so if we go here all cells of course are going to have cytoplasm
or cytosol. And they're going to have ribosomes. However, bacteria ribosomes look a little
different than ours. But if we move our way out, they're going to have a plasma membrane.
So they're going to have a lipid bilayer. But outside of that they're going to have
a cell wall. And so bacteria are going to have a cell wall. And that cell wall is going
to be made up of a chemical called peptidoglycan. And peptidoglycan is polysaccharide. But it's
going to have all of these cross links between it. So it's a really stable structure. It's
going to be different than the cell wall that we'd find in plants. And different from the
cell wall that we'd find in fungi. And remember, we don't have a cell wall. Now luckily we
can target this. So a lot of antibiotics like penicillin for example is going to punch holes
in that peptidoglycan in the cell wall. It's going to lyse the cell. And we can take a
whole bunch of penicillin, as long as we're not allergic to it, and it's not going to
impact us because we don't have that cell wall. Okay. So they got a cell wall. And then
as we move our way out, the next thing is going to be a capsule. A capsule is going
to be like polysaccharide. So it's going to be this jelly like material. And then lots
of times you'll have pilli that will move outside of that. So these little appendages
on it. Now we can get some movement in a bacteria from these pilli, but most of that movement
in a bacteria is just going to come from a flagella. Which is just going to move around
and allow that bacteria to move. Again it's really really small. These are really really
microscopic. But the pilli are going to allow them to grab on to material. And then this
capsule is going to allow them to, for example, to start forming a biofilm. Another thing
about the pilli is that that's going to be where those antibodies grab one. And so as
the pilli change then we're not going to be immune to that. We're not going to make those,
the antibodies to that specific type of bacteria. So these are the structures of a bacteria
that's shared by all bacteria. But they have a ton of different shapes or a ton of different
morphologies. And so a lot of them are going to be this spherical shape. We call that cocci.
A lot of them are going to be this bacilli shape. So e. coli being an example of this.
Or like strep throat is going to be a bacteria. Strepto means strings of cocci or this spherical
shape. Staphylococci, maybe you've heard of like staph, food poisoning. So that's going
to be their morphology that they have. But some are going to be spiral. Some are going
to be vibrio shape. Some are going to be these spirochete. So there's a whole bunch of different
shapes. And we'll classify according to that shape. And then the other way that we can
classify them is using what's called a gram stain. So gram stain is going to use chemicals
to stain the bacteria. Because they don't really show up under a microscope unless we
stain them. But there are basically two types of bacteria. What are called gram negative,
and what they'll have is a plasma membrane. So they're going to have a membrane. Then
they're going to have that layer of peptidoglycan, that cell wall. And then they're going to
have another membrane on the outside. And so when they stain it, they're not going to
stain as brightly. And so we're going to call those gram negative. These are some of the
nastier types of bacteria because it's hard for us to get to that peptidoglycan layer.
And then we're going to have gram positive. So they're basically going to have this lipid
bilayer and then they're going to have the peptidoglycan on the outside. And so you can
see they're going to be much darker in color. And so you can classify bacteria by calling
it like a gram positive staphylococci. But there's going to be hundreds of different
varieties of that. And each of those are going to have different metabolism. And so what
do they eat? How do they make a living? Well they pretty much do it in every way possible.
And so there are three different types of nutritional types. What are called phototrophs.
You can think of that. It's light eaters. Lithotrophs. So that's going to be like earth
eaters. And then organotrophs. So like living eaters or the eaters of life. And so basically
there are two ways that we can classify them. First one is going to be where do they get
their energy. So they could get it from sunlight, inorganic compounds, so that is going to be
just chemicals, or organic compounds. And then where do they get their carbon from?
So it would be important to kind of mention where we are. So we are going to be what's
called a chemoheterotroph. And so we're going to get our energy from the food that we eat
or organic compounds. And then we're going to get our carbon from organic compounds as
well. So we're what's called a chemoheterotroph. But there are going to be a whole different
variety of lives that bacteria can live. In other words some of them will get their source
of energy from inorganic compounds. And then they'll fix carbon out of the atmosphere.
We call those lithoautotrophs. And so what are the two major groups? Because you're going
to have bacteria in all six of these groups. Well we would have the photoautotrophs. An
example of that in eukaryotic cells would be like plants. But in bacteria it's going
to be algae like these blue green algae. So they're getting energy from the sun and then
they're getting their carbon from the atmosphere. Or chemoheterotrophs are going to be like
us. And so most bacteria are going to be of that type. So like e. coli. They're eating
their food and then they're doing cellul respiration. Getting the carbon from that food. So how
do they reproduce? Well they don't do mitosis or meiosis. What they do is they reproduce
through a process called binary fission. So basically what they'll do is they'll copy
that nucleoid region and then it's simply splits in half. And so we'll get two. And
those two split in half and it just keeps splitting in half. And so basically what you
get are a bunch of bacteria. And all of those bacteria are going to be identical to that
first bacteria. And so that's going to be really quick. Sometimes it's as fast as like
20 minutes for them to just make a reproduction. So you can make them really quick. Really,
really fast. However, they're all genetically identical to that first bacteria. As long
as we don't have mutations. And so you might think that makes them easy targets are far
as natural selection goes. But then they have these elements that they can swap between
each other. So they can let go of DNA. And that can be either released into the atmosphere
and picked up by another bacteria. They have these plasmids that they can release and can
transform other bacteria. Bacteria can come together and transfer plasmids between them.
There can be viruses that release the, take the DNA from one bacteria and bring it to
another. And so these are all forms of I would call biological sex. In other words ways that
we can create new bacteria without doing the steps of mito, excuse me, of meiosis and all
of that crossing over. So an example. Let's say that you take a, let's say you have tuberculosis.
And you start taking antibiotics but you don't take all of the antibiotics. Well you're going
to kill all of the bacteria that are susceptible to antibiotics. But you're going to leave
those behind that have some resistance. And a lot of that resistance will be found in
these plasmids. Well now the bacteria that are left can actually transfer those plasmids
to another bacteria giving them resistance. And so then they can grow. And so it's a really
quick way for them to get a huge amount of variability. There's actually three ways they
transfer that. Transformation is picking up something loose in the environment. We have
conjugation. It's the closest to actual sex, where pilus will attach between two and they
can share genetic information. And then the last one is going to be transduction. When
a virus infects one and then infects another. So we used to think they were fairly simple.
That bacteria just lived this kind of lonely life. Or we call that a planktonic life. And
so a great study was done in the 1980s on vibrio fischeri which is a type of bacteria
that when it's alone in the ocean by itself it doesn't make any kind of a color. But if
you get it living together in a colony. If there's a bunch of them close to each other,
then they can start to glow. So it's like they were talking to each other. And in fact
the bobtail squid uses these vibrio fischeri inside it to illuminate. And so especially
these eye pouches right here. And so scientists finally figured out how they communicate.
And they communicate through a process called quorum sensing. So basically a bacteria is
going to give off chemicals. And we call those autoinducers. Some of them will be picked
up by bacteria of the same species. But some of them are going to be given off and they're
going to be picked up by all bacteria in an area. And so if you're just by yourself, nobody
is going to hear that message. But if there's more bacteria, and more bacteria, eventually
they're are going to be so many autoinducers that those are going to trigger genes to be
released. And so is this case it would trigger a luciferase gene which would make all of
them glow. And so basically bacteria are working together, communicating with each other to
say how crowded it is. Or maybe to start increasing virulence so they can actually start promoting
a disease. And so this is a great area of research that is going on as far as stopping
bacterial growth. Because we've figured out if you just treat them with antibiotics they
quickly evolve around that. And so if we could somehow target the communication that would
be another great way that we could kind of stop bacteria. At least the evil ones. And
so that's domain bacteria. Incredibly important. Incredibly complex. And we seem to learn something
new everyday. And I hope that's helpful.