Microbiologist Answers Microbiology Questions From Twitter

I'm Dan Buckley.

I study microbes.

Let's answer your questions from the internet.

This is Microbiology Support.

[upbeat music]

So @culturepulp asks,

Wait, are there actual brain-eating amoebas?

Yes, yes there are.

The good news is

that only a few people every year in North America

end up running into one of these organisms,

and if they do, there's not a lot of hope for you.

Many of these cases are lethal.

For example, there can be infections in Texas

or sometimes in Mexico.

The way that this happens

might be if you jump off a rock face into really warm water,

and the water just goes [imitates water splashing]

right up your nose.

If it has one of these amoeba,

an amoeba called Naegleria fowleri

might be able to get access to your brain.

It's not designed to eat your brain,

but if it finds itself up there,

it's gonna start eating and growing and dividing,

and dividing and dividing

until you have millions and millions and millions

of brain-eating amoebas up there.

@bhive01 asks,

Does the smell of farts tell you a lot

about the microbiome of the gut?

I assume a lot of it is driven by what we eat.

Farts are 100% microbial.

The microbes in your gut

are helping you to digest your food,

and when they break that down,

they break it down into nutrients.

You can also get volatile fatty acids.

So volatile fatty acids

are small molecules like propionate, acetate, and butyrate.

So when you smell poop,

what you're really probably smelling is butyrate.

Normally, if your gut is functioning properly,

these volatile fatty acids are being absorbed by your cells

because they're a source of energy.

That's where you get a lot of the energy

from these microbes in your gut.

But if you've got an imbalance in that system

'cause you ate something bad,

then some of these volatile fatty acids

are gonna come out with those farts,

and that's when things are gonna start to stink.

So if you ever smell garbage

that's been sitting out on the street for a few days,

you'll start to get these volatile fatty acid smells.

You can also get methane out of your gut.

So about a third of human beings have methanogens.

Methanogens use hydrogen and CO2,

and they turn it into methane.

These people, as well as people who make a lotta hydrogen,

are maybe the people who are able

to light their farts on fire, if you've ever seen that.

You'll also smell sulfur.

If you eat a lot of protein,

that protein is gonna have some sulfur in it,

and the bacteria in your gut when they break down that,

they can make a gas called hydrogen sulfide,

and hydrogen sulfide smells like rotten eggs.

So yeah, the smells you're getting

are controlled by what you eat,

but very much it's the microbes

that make 100% of those smells.

@GotherineFoxx asks, Do microbes dance?

If so, how many could dance on the head of a pin?

The head of a pin is pretty pointy,

maybe two microns, give or take,

but a bacterium is typically about the size of two microns.

So if we were to zoom way in,

we would see that it would have just about enough room

for maybe one microbe, maybe two microbes.

@eddwilson asks, If the number of microbial cells in a body

is of the same order as that of human cells,

how much of my weight is microbes?

Add up all the cells in your body,

and then add up all of the microbial cells in your body,

you find that they're actually about the same.

Microbial cells, bacteria in particular,

are about 1,000 times smaller than human cells.

So if we add up all of the mass of the bacterial cells,

you're gonna find that that's two to six pounds,

so a couple of kilograms.

And that'll change throughout the day, right?

Because when you go to the bathroom, when you poop,

that poop is basically solid microbes,

except for maybe the stray corn kernel

or a little bit of lettuce,

you've just lost a couple of pounds of microbes,

but don't worry, they're gonna grow back.

@RoverSuede, What is the fastest bacteria?

Like if I were to stage a little race under a microscope,

who would win?

The fastest bacteria is Bdellovibrio bacteriovorus.

Literally that translates into the wiggly leech

that eats bacteria.

Its real speed is about maybe 150 microns per second,

which is blazingly fast for a microbe.

If we were to shrink ourselves down

to the size of this microbe,

it would be about 600 miles an hour, right?

That's like the speed of a rocket car.

So you find them in fresh water habitats typically.

It's a predator of bacteria,

so they need to be really fast

'cause they're chasing down those bacteria

to try and attach to them and kill them.

You almost can't see them

because you're looking under the microscope

and they sort of go [imitates fast whoosh]

because they're just that fast.

If you wanna look at them under the microscope,

you have to add something really viscous

that's gonna try to slow them down.

@je_suis_cece asks, Predatory bacteria,

that shit is real af.

You are right.

There are tons of predatory bacteria.

So these are bacteria that eat other bacteria.

They come in a lot of different varieties.

There are Myxococcus.

Myxococcus hunt in a wolf pack behavior.

They talk to each other using molecules

so they can zero in on prey,

and then they surround the prey

and secrete enzymes that cause them to dissolve.

There can be epibiotic.

Parasites and predators like vampirovibrio

that latch onto the outside of a cell

and suck its cytoplasm.

And one of the most terrifying is Bdellovibrio.

So Bdellovibrio lives in aquatic habitats,

usually fresh water

where it tracks down its prey.

It will actually attach to the prey

and then it will penetrate the cell wall

and push itself inside of that cell where it will grow.

It will replicate several times to make maybe 8 or 10

or as many as 12 cells

inside of the guts of the the prey cell that it's attacking.

And then when it's done,

they explode out and they swarm out.

@MitchBrown43, My biology test was like,

'How do most bacteria move?

A, magic?'

I didn't even need to read the rest of the answers.

Bacteria move through a process called chemotaxis.

Bacteria don't have eyes or ears like you or I,

so they don't know where they're going.

And so they do what we call a biased random walk.

They keep sampling over time.

Is it good, is it better?

They definitely move towards food.

So they can sense if the food concentration is high.

And if it's bad or if it's getting worse,

they just like shake themselves up,

swim off randomly in a new direction,

and through this random series of runs and tumbles,

they actually are really effective

at finding the right way to go.

And then how do they get there?

Well, there's lots of different ways that microbes move.

So many microbes have a flagella,

usually stiff and helical shaped.

It spins and propels them and helps them wiggle,

but then when they wanna run,

they turn those flagella in the right direction

and they all sort of coil up with each other

and that allows the bacteria to shoot forward.

Some bacteria also move by what we call gliding.

They sort of drive themselves along the surface

with these suction cups.

They're just one little cell out in the world,

and so they need to find conditions that are right for them.

Temperature, light, nutrients, salinity.

They sense all of these things

and then try to use this biased random walk

to get where they need to go.

@newstart_2024.

'The Last of Us' zombie infection is real.

Fungi can devour insects from the inside out

and experts say it's not too far-fetched

that a similar parasite could evolve to infect humans.

The clickers that you saw

where the fungus infects people

coming out of the person's head,

I wouldn't worry too much about that

unless you're an insect.

The Ophiocordyceps fungus

infects many different kinds of insects,

gets into their brain

and then causes these insects to move in such a way

that promotes the distribution of the fungus

so that more ants will become zombies.

But insects are cold-blooded.

They're very different from us.

And so I wouldn't think that this fungus

is gonna infect people.

If I was worried about a zombie infection for people,

I would really think about rabies.

Rabies is transmitted by a bite,

and if you are not vaccinated or treated quickly,

it basically gets to your brain.

It can make you maybe wanna bite people.

So we kind of do have a zombie infection.

We just have really good vaccines for it right now.

@SublimeKarnage, What microbe scares you the most?

Honestly, following the newspaper,

it's avian influenza.

There's been avian influenza around for decades.

The reason it's a problem now

is there is a pandemic among the birds.

It's all over North America.

There are farmers who are dealing with this right now.

Their chickens are getting sick,

their turkeys are getting sick,

but it's a big problem for us too,

'cause that avian influenza can make people sick.

40 or more million people died in 1918

from the first flu pandemic,

but then flu became seasonal.

Then we have this avian flu.

If those two flus happen to infect one person,

those two strains of flu can recombine,

part avian influenza and human influenza.

It's a little bit of both and neither 100% of either,

and that's completely new.

Our bodies have not seen that before.

And so your prior vaccination won't matter.

This will be a new pandemic

that will be very problematic.

@NikuKazori asks, I'm just shocked

there's a bacteria that eats metal.

What in tarnation?

There are lots of bacteria that eat metal.

There are organisms that can eat chrome,

they can eat uranium, they can eat all sorts of metals.

They actually, in a real sense, breathe the metal.

It's a kind of respiration.

So all living things get energy

by moving electrons from one place to another.

Many of them will have something called nano wires,

really small wires.

So they conduct electricity.

And so the microbes can then move electrons

through that wire,

either put those electrons down onto the surface

or pull electrons off of the surface.

And when it comes to organisms like iron reducing bacteria,

they're actually taking those electrons through the wires

and putting them down onto a metal

and causing that metal to be reduced.

When we take electrons off of metal, for example, iron,

we are oxidizing it and oxidizing metal is rust.

And if you look at pipes in factories or in pipelines,

or in boats, the pitting and the rusting of that metal

is often catalyzed by microbes

who are basically living off of that metal itself.

@Cern_lXXl asks,

How can bacteria become resistant to antibiotics?

So anytime there's a new change in the environment,

the microbes are gonna try to evolve in response to that

so that they can be more successful.

When we discovered antibiotics,

we discovered those antibiotics

because they were made by fungi

and bacteria that live in soil.

Those bacteria and fungi make antibiotics

to kill each other.

They're fighting with each other all the time,

but then those organisms are gonna evolve resistance

and they've had hundreds of millions of years

of these back and forth warring with antibiotics

and then antibiotic resistance genes.

So we've been using antibiotics

since like the 1930s and 1940s.

The first antibiotics came from fungi.

Scientists by the name of Fleming discovered penicillium

that makes penicillin,

which was one of our first antibiotics.

And there was also a really important discovery

of streptomycin by a scientist

by the name of Selman Waksman,

who is a soil microbiologist, much like myself.

So we've discovered the antibiotics, woo-hoo, right?

We can make antibiotics too, just like bacteria do.

Well, the bacteria already have countermeasures.

And if those genes

and those organisms come in contact with our pathogens,

those pathogens, they go to the app store,

they're like, hey,

do you have any antibiotic resistant genes

that might be useful to me?

And if they're useful, horizontal gene transfer

gives you a conduit to get those genes.

Evolution does the rest, right?

Now we have antibiotic resistant pathogens.

Antibiotic resistance in general is a real serious problem.

And the way to fight it is to try and figure out

how these organisms are evolving and try

and use our antibiotics in a way that slows down

that pace of evolution so that the antibiotics

are more effective for longer time.

@SibsTHFC asks, can bacteria survive high temperatures

and microwave radiation?

Do we really need to clean out our microwaves?

The reason you want to clean your microwave

is because all that food just gets nasty in there.

It's not because there are organisms

that are evolving to be resistant to that radiation.

The microbes in your microwave

are gonna be mostly like the ones we see on our sponge,

right?

They're gonna be staphylococcus,

they're gonna be bacillus, maybe some pseudomonas,

so probably they're gonna end up dying in your microwave.

Microbes themselves can survive really high temperatures.

I think the record microbe

can survive temperatures at 250 degrees Fahrenheit,

and we definitely have microbes

that can survive high radiation.

So there's an organism

by the name of deinococcus radiodurans,

the terrible radiation resistant ball.

This organism is able to withstand 5,000 grays of radiation.

People would be dead after maybe five grays of radiation.

So deinococcus is one of the most radiation resistant

organisms on the planet.

In fact, NASA has done experiments.

They've found that deinococcus can live for years in space.

Many of these organisms

that live in these unusual environments,

we refer to them as extremophiles.

@iosilverlining asks, oh, dear God,

what are extremophiles?

We use this term extremophile to refer to microbes

that thrive under conditions

that would be pretty much lethal for most other organisms.

We have thermophiles, which like really high temperatures

like pyrococcus furiosus, the furious, flaming fireball.

Pyrococcus furiosus can live at temperatures

above the boiling point of water.

In fact, it thrives in those conditions.

At the bottom of the ocean, there's really high pressure,

that really high pressure

changes the boiling point of water.

And so we can have organisms like pyrococcus

living at volcanic seeps at the bottom of the ocean.

We also have acidophils.

There are organisms that live in acid mine drainage.

So this is like the runoff from a mining operation

where the pH is 0.5, that's pure sulfuric acid.

You can almost watch a nail rust under these conditions.

But this is home for these guys.

If there's liquid water, probably you have a microbe there.

And probably they've been living happily there

for millions of years.

@silorchoon asks us, I'm doing microbiology

and I genuinely don't know the difference between bacteria,

fungi, and viruses.

What a joke.

Microorganisms in general are just anything smaller

than what you can see.

We have some that are called cells.

Cells have a membrane, they have a cytoplasm.

We have one kind called a prokaryote, which is an organism

that has no nucleus.

It came first, they evolved 4 billion years ago

and they split into two groups, bacteria and archea.

Eukaryote cells evolved much later.

Eukaryote have a nucleus,

and many of the karate cells are single-celled organisms,

but they evolved into dogs and cats and plants

and all the macroorganisms that we see today.

Then there's fungi, eukaryotic organisms.

Maybe they live in soil,

maybe they look a little bit like this guy.

And then the bacteria

would look a little bit more like this,

a little bit more slimy, a lot less fuzzy.

You have cells, viruses,

and that's most of your microbial world.

Spacescisteph asks, I just learned like 10 seconds ago

that there are magnetic bacteria.

There are magnetic bacteria.

Magnetic bacteria have little magnets

that are inside of their cytoplasm

that help the bacteria line themselves up

with magnetic fields.

They use that like a compass

that helps them change directions.

Why would a bacterium need a magnet?

We live on a sphere, right?

The magnetic pole is not directly north,

it's actually directed a little bit down.

So if I were to point straight towards the magnetic north,

it would be in that direction.

And so bacteria know this, right?

So when they're swimming north,

they're actually swimming down.

And so these bacteria live in sediments

usually where you have water overlaying sand

or something like that.

There's oxygen up here and there's no oxygen down there.

By swimming north to go down and south to go up,

they can position themselves in the right position

with respect to oxygen.

And in fact, there was a group in Europe,

they invented a micro manipulator

that controlled some magnets and they attached it

to an old Nintendo video game controller

and get the microbes to of swim around

and do whatever dance they wanted.

They actually put it to music.

You could look it up on YouTube.

@AshleyMaria asks, ever wonder what kind of germs

are on the subway poles you hold?

Microbes need water to live.

So wherever you have water,

you're probably gonna have a lot of microbes.

The subway pole, it's dry.

There's actually pretty few microbes on there,

but if we did find microbes in there,

it's probably from one or two sources, right?

The one source is us, our skin constantly sloughs off.

And because our skin is covered with microbes,

when we slough off that skin, the microbes come off too.

And so anytime you're in an indoor environment,

the dominant microbes are gonna be those microbes

associated with skin.

One of our more common organisms is staphylococcus.

This is a scanning electron microscopic image

of some bacteria that someone grew from a surface,

not dissimilar from your subway pole.

These little balls of grapes,

these are staphylococcus aureus,

which is one of the most common organisms on our skin

that's called aureus because it makes a gold color

when it grows on a Petri plate.

Most of the staff that you're gonna encounter

is not dangerous.

But there are some staff

that have antibiotic resistance genes, that have toxin genes

that can cause a pretty bad infection.

So if you get an infection in a hospital,

it's probably from a multi-drug resistant staph aureus

or methicillin resistant staph aureus.

Probably the organism on your pole in the subway

is not methicillin resistant staph aureus.

But once we move outside,

one of the things that would grow most vigorously

and we see most common is an organism called bacillus

such as bacillus subtilis

or maybe bacillus megaterium, bacillus cereus.

This sort of wrinkly organism you're looking at right here.

They live in soil, but because they make spores,

they can survive a long time.

@HaileyMarieP says, I love tardigrades.

How do they survive LMAO?

Well, tardigrades are kind of crazy.

They are microorganisms.

They are eukaryotics.

So they're made of cells that have a nuclear,

they're multicellular,

which is different from a lot of the microorganisms

we've been talking about here.

This is a very unusual and unique shape.

It's not something we see a lot of in the microbial world.

They are able to survive really harsh conditions

by allowing themselves to be completely desiccated.

The key too is that when you rehydrate them,

so you had a drop of water to this guy, you know, boom,

he's ready to go.

@hoadventures asks,

why does cat poop have to be bad for pregnant people?

All I want is a cat rn.

Cat poop can carry the cysts of toxoplasma.

Toxoplasma is a parasite,

it's not usually harmful to people,

but it can cross a placenta and infect embryos

and infect fetuses, and it is a cause of miscarriage.

And so if you're pregnant,

you definitely wanna avoid the cat poop.

Toxoplasma is actually a really interesting organism.

Here we're seeing a toxoplasma next to our red blood cells.

It cycles between different animals,

so it's often found infecting mice.

This parasite toxoplasma affects the mouse's brain

and makes it more likely that that mouse

is gonna get himself killed by a cat.

That actually helps the parasite

because when the cat eats him,

it ends up in the poop of the cat.

So this is a way for these cysts to get spread wider

and wider.

@hoadventures, if you really wanted to have a cat,

have an indoor cat,

indoor cats are less likely to be exposed to toxoplasma.

Or if you had somebody else in your household

clean the litter.

@GeneralCatana wants to know,

but do amoebas [beep]

no, amoebas don't [beep]

Amoebas are asexual.

They divide by binary fission

that they split into two cells.

Amoeba are in a group of organisms called protists.

So protists have evolved many different ways of doing sex.

And pro can also engage in something that bacteria do,

which is called horizontal gene transfer,

which is where maybe you move individual pieces of DNA

back and forth as well.

@maxlarter asks,

how the duck does horizontal gene transfer work in viruses?

We use the term horizontal to contrast from vertical.

And vertical transfer, this is like a family tree.

You have your great grandparents, then your grandparents,

then your parents, then you.

Horizontally is like taking DNA from you and sending it

to somebody you've never met before.

That's something that microbes do all the time,

and it's super important for the revolution.

So for viruses, this is kind of tricky

'cause viruses are not cells.

Viruses are basically just a chunk of nucleic acid

with a little bit of protein around it.

So how do they exchange information?

Well, they do it when they're in a cell

and while they're inside of a cell, they're making copies.

Lots of little baby viruses.

When they're doing this,

they could pick up a piece of DNA from the bacterial genome,

and then when they package a new baby virus

and it goes out into the world, it's picked up that DNA.

So the virus wins by giving these genes to the cells,

which then make those cells more effective pathogens.

And so this horizontal transfer is just super important

for the evolution of microorganisms.

We have a question from @Sadithaanuhas2.

What's the largest bacteria found so far?

The largest bacteria currently is thiomargarita magnifica.

Magnifica two centimeters long

and about 50 microns in diameter.

So this is almost the size of a human hair.

So it's something you could see with your eyes.

It was only discovered about two years ago,

living in the mangroves.

People saw these sort of fuzzy things

and thought, what could that possibly be?

But looked at it on the microscope

and found out, hey, this is actually a bacterium.

@SolBrah asks, did you know the little creatures

in your gut control your cravings?

They themselves want the sugar, et cetera, processed foods.

The cravings stop after a while

because of the microbiome that was eating the garbage

dies out.

This is actually plausible.

Microbes in your gut are playing a really important role,

they're helping you to break down your food.

In fact, pretty much all the plant material you eat,

you would be unable to digest those

without the bacteria in your large intestine.

They break it down into materials that are nutrients for us,

but they also make other chemicals too.

Some of these chemicals can cross into your blood,

some of these molecules are very similar to hormones

that can control how we feel.

So how hungry we are or how full we feel or maybe our moods.

There have been experiments in mice

that have provided evidence to support

that changes in your gut composition

could affect your behaviors.

Hard to do these experiments with people,

but certainly this is plausible.

@RuthVmd asks, how about fecal transplant

for improved microbiome?

We take antibiotics all the time to treat infections,

but the antibiotics, they kill microbes

so they're gonna kill a lot of the microbes in your gut.

And if you take antibiotics often you'll find

that you'll end up with diarrhea.

Usually this just resolves itself,

your microbes will grow back.

But sometimes there can be an organism

called clostridium difficile.

And you can think of this as like a weed,

it's an organism that if it's too abundant,

it becomes a problem.

Often, C. Diff as we call it, is resistant to antibiotics

And so when you take those antibiotics,

they kill off your healthy microbes

and C. diff doesn't get killed off.

And because it's like a weed, it can grow and take over.

You could dies from a C. Diff infection.

And so the best treatment right now

for this kind infection is a fecal transplant.

You'd get a donor,

usually that's gonna be a member of your family,

and you'd make the nastiest milkshake ever,

put this stuff in a blender.

You'd mix it up into a slurry, you'd put it into a tube,

and then the tube goes where the sun don't shine.

You can reintroduce, sorry for that,

the healthy kind of organisms,

and once you have your healthy microbiome back,

it will suppress this disease and cure it.

At lemiotw, so what do microbiologists do

when there isn't a pandemic endangering lives?

There's a lot to do.

Microbes are the most diverse organisms on the planet.

Only about maybe 10,000 or 20,000 of them

have been described.

Most of them have yet to be discovered,

they've yet to be named.

And when we're not doing that,

we're also trying to predict the next pandemic.

So if you would've asked a microbiologist 20 years ago,

what are the most dangerous, scary microbes out there?

Coronavirus even 20 years ago would've made the top five.

And that's because we know that a lot of viruses from bats

can jump over and infect people.

And so when this pandemic started,

we were really poised to move quickly.

The fact that we were able to get a vaccine in a year

is an indication of how much work

microbiologists were doing in the off season.

At luboskolouch asks, NASA's perseverance rover

just found something wild on Mars.

Not saying it's aliens,

but this rock has features super similar

to what microbes would leave behind

if Mars was teeming with life billions of years ago,

what do you think?

I think it's likely that there might have been life on Mars.

The rocks that NASA just found on Mars

have a couple of really interesting characteristics.

Number one, they're sedimentary rocks.

So they're rocks that were formed underwater,

and we know that water is really important for life.

The other thing that's really important about these rocks

is they have evidence of organic molecules.

Molecules typically associated with living things.

They can be food for cells,

but also the cells when they die,

their little dead bodies make organic molecules.

But those rocks, if they can bring them back to earth,

we would be able to determine whether

or not those organics are biosignatures or evidence of life.

So the real limitation on Mars

is that it's very dry right now,

but in the past it's been wet.

So the question was, did microbes live in the past?

If they still live, the question would be,

are they living probably underground?

At NileFM asks, you'll find more germs and bacteria

on a tablet or mobile phone screen than on a toilet seat.

Is this true or false?

That would actually be true.

If we were to look at both of these surfaces,

they're very dry and they're also often wiped down

and they're very smooth.

And so as a consequence,

there's not gonna be a whole lot of bacteria

on either one of them.

If you do wanna look for bacteria, you can look right there.

So keyboards have a lot of bacteria,

and the reason for that is they collect dust, right?

There's lots of space in between those keys.

One of the places you're gonna find the most gnarly stuff

is your kitchen sponge or your wash rag.

And that's because it's often wet,

it's often getting a lot of food, right?

There's a lot of surface area 'cause it's porous.

So the microbes can live, survive, and grow in that.

And so you definitely wanna let that thing dry out

and you wanna wash it frequently.

If you have a fish tank, that is full of microbes,

particularly that filter in the back,

that's like a rainforest living in that thing.

At waterwolf4 asks,

did you know there are more beneficial microbes

in 10 square meters of healthy soil

than all other animal and plant species on the planet?

#organic

Just to give you an idea about how complicated

the soil microbial community is,

we could look at say a 10 meter square section of soil

10 centimeters deep

because that's where the best soil is gonna be.

We'd have about 12 million grams of soil in that patch.

We have about one times 10 to nine bacteria

per gram of soil,

that's a billion bacteria per gram.

We multiply those, we have 1.2 times 10 to the 16 bacteria

just in that outdoor backyard patch.

If we line those guys up end to end,

10 to the 16th bacteria, each one is about one micron long.

We would find we have about 10 billion with a B

meters of bacteria, enough to get to the moon

and beyond about 30 times of bacteria lined up end to end

living in that 10 square meter patch of soil.

So our next question is from at Marlenemz,

how do microbiologists leave their house

after knowing what they know?

One thing you learn when you're a microbiologist

is everything you touch, everything you eat,

everything you drink is full of microbes.

If we had people coming to this planet,

they could be mistaken for thinking

that the dominant form of life is microbial

'cause most cells on this planet are microbes.

And the secret is, most microbes don't hurt you.

One of the really important jobs that microbes do

is to make the oxygen in the air that we breathe.

30% of our oxygen is coming from plants,

but most of it comes from microbes.

Billions of years ago, there's no oxygen, hydrogen sulfide,

toxic gases, uninhabitable planet.

But once the cyanobacteria show up,

they turn it into a world that we can live on.

We couldn't live on this earth without the microbes

doing their job for us.

At DanielSprocket, calling all #microbe tweeps,

what do you think is the most important

or interesting unanswered question in #microbiology?

The vast majority of microbes out there in the world,

the super mass majority, we don't know anything about them.

It's very difficult to identify these microbes

under the microscope.

Most of the microbes, when we put them on a Petri plate,

they just don't grow.

So within the last 10 or 15 years,

we've developed genomic technologies like metagenomics

when we sequence all of the DNA from a particular sample.

And so if we have something like soil, it has thousands,

tens of thousands of different species.

They all have genomes, so there's millions of genes.

We can sequence all of their DNA,

like a great big jigsaw puzzle.

And when we do that,

we see that the vast majority of these species

don't match anything that we've described.

Microbiologists call this microbial dark matter.

When we think about dark matter in terms of astronomy,

we think about this material

that sort of holds the shape of the universe together,

which you can't really see in a telescope.

We don't know what it is, but it's out there.

Well, it's the same with microbes.

At Evanpro asks,

can microbiologists identify common bacteria by smell?

Like can they smell a wet towel

or a dumpster or wilted broccoli and say, ah,

good old Clostridium perfringens?

Or do bacteria mostly smell the same?

We can identify a lot of smells

that are associated with certain organisms or processes.

For example, there are organisms called pseudomonas.

If you smell them, lift the plate up and do one of these.

If you got the smell of grape jelly,

that might give you a clue that that's a pseudomonas.

So many pseudomonas smell like grapes.

There's an organism I study called Streptomyces

Streptomyces live in soil.

If you've ever gone outside after the rain

and you smell that earthy goodness, right?

That's actually the odor made by these Streptomyces,

so they make a compound called geosmin,

and that's what you're smelling

when you smell the rain hit the soil.

So those are all the questions for today.

Thanks for watching Microbiology Support.