Chapter 16: Phylogenetic Diversity of Bacteria

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All right, welcome to the Deep Dive, where we dive deep into the sources that you're curious about.

And today we're tackling, well, a pretty big one.

Yeah, I'd say so.

You sent us some excerpts from 16 .pdf, which, let's be honest, that title doesn't give much away.

But the content is fascinating.

We're talking about bacteria.

The unseen majority, as I like to think of them.

Exactly.

And I think it's clear from the sources you sent that you want to go beyond the headlines, beyond just bacteria or germs.

Absolutely.

So today we're exploring the sheer variety of bacterial life, their different ways of surviving, and honestly, some of their superpowers that impact us and the whole planet.

It's going to be a wild ride through different phyla, different classes.

We'll be busting some myths along the way, too.

Exactly.

So, strap yourselves in.

First stop, the proteobacteria.

This phylum is like the VIP section of the bacterial world.

Yeah, that's a good way to put it.

Not just the largest group, but the most diverse when it comes to how they get their energy, how they live.

Okay, so right off the bat, gram negative.

Our term.

Right.

So think of it like this.

Gram negative bacteria, they have this extra layer of protection around their cells, an outer membrane.

This matters for a bunch of reasons, like how they interact with antibiotics, for example.

Makes sense.

But what's really cool about proteobacteria is how they get their energy.

It's not just one size fits all.

Some are like us, needing oxygen.

Others can switch it up using oxygen if it's around, but not strictly needing it.

And then you've got those that use chemicals like inorganic stuff from rocks or even light.

Talk about versatile.

It's amazing.

They're like little survival experts.

And our source even mentions finding the same energy making process in totally different classes within proteobacteria.

How does that even happen?

That's where things get really wild.

It's all about horizontal gene transfer.

Imagine bacteria swapping genes like trading cards.

It's this sharing of genetic material that lets them pick up new metabolic tricks.

So yeah, they have a common ancestor way back, but they've also picked up skills along the way, like a bacterial skillshare program.

Love that analogy.

Okay.

So let's zoom in on these classes, starting with the alpha proteobacteria.

Second largest, according to the source, about a thousand species described.

What are some of the defining features?

Well, alpha proteobacteria are all about diversity function.

As I said, many need or can use oxygen and a good chunk are oligotrophic, meaning they're the minimalists of the bacterial world surviving on very few nutrients.

But within this class, the real stars are the rhizobialis, the largest order and boy, are they metabolically gifted.

Rhizobialis.

Wait, is that where we find the rhizobia?

The ones that team up with plants like in those root nodules to get nitrogen from the air.

You got it.

Rhizobia are all about partnership.

They form these symbiotic relationships, win -win situations with plants, especially legumes, think beans, peas, clover.

They take nitrogen from the air, turn it into a form plants can use.

It's like a natural fertilizer factory.

Amazing.

And get this, the genes for making those root nodules, they're often on plasmids, those little bits of DNA that can be swapped between bacteria.

Sharing is caring, right?

Definitely in this case.

The source lists a bunch of rhizobial genera, braderhizobium, okra -bactrim, azorhizobium, and a ton more.

Each one seems to have its preferred plant partners too.

Yeah, it's a whole network of relationships evolved over millions of years.

Now, the source brings up a bit of a family drama here.

It talks about agrobacterium tumifatians, now called rhizobium radiobacter.

Closely related to the helpful rhizobia, but instead of helping plants, it causes crown gull disease.

What's going on there?

Ah, yeah, a bit of a black sheep in the family.

So it's related, but instead of helping, it manipulates the plant cells, making these tumor -like growths, the crown balls.

And again, the genes for this trickery, they're on plasmids, but totally different from the ones used for making nodules.

So same tool, different outcome.

Exactly.

Shows how just a few genes can completely change a bacterium's relationship with its host.

Now, what about methylobacterium?

The source describes them as pink pigmented, facultative methylotrophs.

I think I need a pronunciation guide for that one.

Yeah, it's a mouthful.

But the name tells you a lot.

They're pink thanks to their pigments.

They're methylotrophs, meaning they use methanol as their fuel, like think simple alcohol.

And facultative means they can use oxygen or not.

And you can find these guys everywhere, plant leaves, soil, even your showerhead, sometimes forming those pinkish biofilms.

Oh, interesting.

They're pretty specialized in what they eat, though.

If you want to isolate them in the lab, you can literally just press a plant leaf onto a petri dish with methanol as the food.

They'll grow happily.

That's so cool.

From plant partners to shower guests, the alpha proteobacteria are quite the bunch.

What about Bartonella?

That rings a bell like from a health perspective.

Yeah, you're right.

Bartonella, they used to be

intracellular pathogens, meaning they live inside their host cells.

And they get around by hitching rides on arthropods like fleas, lice, sandflies.

Bartonella quintana, that's the one that caused trench fever back in World War I.

Wow, I didn't know that.

Yeah.

And other Bartonella species can cause cat scratch disease, which, as the name suggests, you can get from a scratch or bite from an infected cat.

Unlike some other intracellular bacteria, they tend to stay on the surface of host cells instead of burrowing deep inside.

Interesting strategy.

Now, last but not least in the Rhizobialis, there's Pilegebacter ubeke.

And the source claims it might be the most abundant bacterial species on Earth.

That's a pretty bold statement.

It is, but it might be true.

Pilegebacter ubeke, it loves low nutrient environments and uses organic matter for energy.

You find it mostly in the sunny upper layer of the ocean, the photic zone.

Estimates say it could make up a huge hump of all bacteria in those surface waters.

And considering how vast the ocean is, well, it could very well be the champion of abundance.

It definitely makes you think about life's priorities, right?

We humans think we're a big deal, but this tiny bacterium might outnumber us by far.

It's humbling, to say the least.

Okay, let's shift gears to the Rickettsiales.

The source mentions they're all about living inside animal cells, either as parasites or in beneficial relationships.

And apparently scientists haven't even figured out how to grow them in the lab without a host.

Yeah, they're tricky, very dependent on their hosts, especially arthropods.

We're talking ticks, mites, fleas, lice.

Rickettsia, that's a genus in this group, and some of them cause pretty nasty human diseases.

Rickettsia proezeki, that's one behind typhus, spread by lice.

Right.

And then there's Rickettsia rickettsii, the culprit of rocky mountain spotted fever, spread by ticks.

Metabolically, they're very specific, mostly using glutamate or glutamine for energy.

They basically need their host for survival.

Now, Wolbachia, that name always pops up when you read about weird things happening in the insect world, like messing with their reproduction, right?

Oh, absolutely.

Wolbachia, they're like the puppet masters of the insect world.

They infect tons of arthropods, insects, spiders, mites, and even some roundworms, and they can pull off some crazy reproductive tricks.

Like what?

Well, they can make females reproduce without mating.

They can kill off male offspring, even turn males into females.

Whoa, that's incredible.

And the source says they don't even have peptidoglycan, which is like a basic building block of most bacterial cell walls.

Yeah, it's surprising, right?

Makes you wonder how they hold themselves together.

But it shows how diverse bacteria can be, even at the most fundamental level.

Before we move on from the alpha proteobacteria, the source briefly mentions a few other orders, like rhodobacteralis and rhodospirulase.

They contain some of those colorful bacteria, right?

Like the purple non -sulfur bacteria?

Exactly.

Those orders are full of metabolic variety.

You've got your purple non -sulfur bacteria, like rhodobacter.

They can do photosynthesis, but don't produce oxygen.

Then there's rhodobacter, an aerobic and oxygenic

a long name, but basically they can use light for energy, but in a different way.

And then you've got azospirulum, a nitrogen fixer, pericoccus, a denitrifier, helping to return nitrogen to the atmosphere,

magnetospirulum, with tiny magnets inside, letting them navigate using the earth's magnetic field.

Wow, those sound like some sci -fi bacteria.

Right.

And we've got acetobacter and gluconobacter, used to make vinegar, colobacter, which divides asymmetrically one daughter cell different from the other, and even sphycomonus, which breaks down those tough aromatic compounds, making them useful for cleaning up pollution.

The alpha proteobacteria are a true testament to evolution's creativity.

For sure.

Okay, let's move on to the beta proteobacteria.

Third largest class, but the source emphasizes their huge functional diversity.

What are some of the standouts?

Okay, so we're talking about 500 or so species, and they've got a variety of lifestyles.

We've got bricoldariels,

hydrogenophilase,

metallophilase, niseriales, nitrosomonadales, and rhodocyclase.

Bricoldariels.

Yeah.

Now, that's a name I've heard before, and I think it was in a medical context.

You're probably right.

The bricoldaria genus, it's a bit of a double -edged sword.

They get energy by breaking down organic compounds, and they do it through respiration using an electron transport chain.

Okay.

Most need oxygen, but some can switch to nitrate if oxygen's low, and a lot of them can fix nitrogen, too.

Plus, they're really good at breaking down those aromatic compounds, making them potentially useful for cleaning up polluted environments.

So good guys so far.

Well, not always.

Some are actually plant or animal pathogens.

It's like a Jekyll and Hyde situation.

Like bricoldariels sapacia, which the source mentions as both a soil dweller and a sometimes nasty pathogen.

Exactly.

Bricoldariels sapacia can actually be good for plants, protecting their roots from some diseases, but it can also cause rot in onions.

And for us humans, it's a real concern in hospitals.

It can cause infections, especially in people with compromised immune systems or cystic fibrosis.

Not good.

Nope.

It forms these tough biofilms, those bacterial communities that resist antibiotics, making it really hard to treat.

So biofilms and antibiotic resistance, that's a dangerous combo.

Yeah.

What about niserialis?

I know niseria is a genus that comes up in health news.

Definitely.

Niserias, they're another diverse group.

The most famous are niseria and chromobacterium.

Niseria, they're usually found in animals, and some are in fact pathogenic.

They're always kachi, meaning they're round shaped.

Some niseria hang out in our mouths without causing harm.

But then you've got the bad guys like niseria meningititis, which causes meningitis, and niseria gonorrhea, the one responsible for gonorrhea.

And chromobacterium is related, but rod shaped, and makes that cool purple pigment,

violacine.

The source says it might have antimicrobial properties.

That's right.

Chromobacterium violacium, you find it in soil and water, especially in warmer climates.

It can grow with or without oxygen, and that purple pigment is pretty amazing.

It doesn't dissolve in water and has been shown to fight off other microbes and act as an antioxidant.

Multitalented.

The source also lists hydrogenophilales, methylophilales, and nitrosomonadales.

They all sound like they're involved in some pretty specific chemistry.

They are.

Hydrogenophilales, with hydrogenophilas as a key player, they get energy by oxidizing hydrogen gas.

They're like hydrogen eaters.

Methylophilales, like methylophilus, they're the methylotrophs, using those simple one carbon compounds for growth.

And nitrosomonadales, with important genera like nitrosomonas and nitrosospora, they're the ammonia oxidizers, crucial in the nitrogen cycle, converting ammonia into nitrite.

And last but not least in the beta proteobacteria, we have the rhodocyclase, with rhodocyclis and zuglia.

Rhodocyclis, they're purple non -sulfur bacteria, kind of like those we saw in the alpha proteobacteria.

They can do photosynthesis without oxygen and prefer those environments with light, but no oxygen.

Zuglia, on the other hand, they're aerobic and known for making this thick, gooey capsule that lets them clump together.

You often see them in wastewater treatment plants forming those flocs?

Okay, buckle up, because we're hitting the gamma proteobacteria next.

And the source claims it's the biggest and most diverse class.

That's saying something after everything we've already covered.

Oh, it's true.

Nearly half of all known proteobacteria belong to the gamma proteobacteria, over 1500 species.

And yes, it includes many human pathogens that we hear about.

They can get energy from light, organic compounds, or inorganic compounds, and some breathe oxygen while others ferment.

They grow fast in the lab, so we know a lot about them, and they live everywhere, from the deep ocean to our guts.

Okay, so we'll need a roadmap for this one.

Definitely.

We're focusing on two main groups, the enterobacteriales, the gut bacteria, and then pseudomonadales and vibrianelles, two very common orders.

Enterobacterial, so we're talking gut bacteria here.

Exactly.

They're a gram -negative, rod -shaped, and don't form spores.

They can have flagella all over their surface, or none at all.

Right.

We use the oxidase and catalase tests in the lab to tell them apart from other gamma proteobacteria.

And the source mentions mixed acid fermenters and butanadial fermenters.

What's that all about?

So that refers to what they produce when they ferment sugars without oxygen.

Mixed acid fermenters like escherichia, salmonella, shigella, and proteus, they make a bunch of acids like lactic, acetic, succinic, formic acid, plus ethanol, carbon dioxide, and hydrogen gas.

Okay, and the butanadial fermenters.

They do something similar, but their main product is 2 .3 -butanediol.

Think of it like slightly different recipes for breaking down sugars without oxygen.

Makes sense.

Let's talk about some of these big names.

Escherichia, probably the most famous one, it's in our gut, can even make vitamin K, which is important for blood clotting.

But then you've got those dangerous E.

coli strains like O157 .H7.

Right.

Most E.

coli are harmless, even helpful.

They live in our gut without causing problems.

But some strains, like O157 .H7, they've picked up nasty genes, often from other bacteria, that make them produce toxins.

And because they can grow with or without oxygen, they help make the gut environment suitable for other microbes that can't tolerate oxygen.

And what about salmonella and shigella?

The source says they're almost always bad news for warm -blooded animals.

Yeah, that's pretty accurate.

Salmonella, they cause a range of illnesses, from typhoid fever to food poisoning.

Shigella, it's a close relative of Escherichia, and it typically causes dysentery in humans.

Okay.

Seems these two have evolved specifically to cause disease.

And then there's Proteus, which the source highlights for its incredible motility and its ability to make urease.

It's often linked to UTIs, right?

Urinary tract infections, yes.

Proteus is a mover and shaker, literally.

It has tons of flagella that let it swim around really fast, and it produces a lot of urease, an enzyme that breaks down urea into ammonia.

This raises the pH in the urinary tract, which can lead to kidney stones and create a better environment for Proteus to grow.

In the lab, it's famous for swarming on agar plates.

It moves outward in waves, forming these cool concentric rings.

So easy to spot under the microscope.

Now let's switch to the

Enterobacter aerogenes, you find it everywhere, in water, sewage, and even our guts.

It can sometimes cause infections, especially UTIs.

Klebsiella pneumonia, it's known for causing pneumonia, but it's more common in soil and water.

And many Klebsiella species can fix nitrogen, which is unusual for gut bacteria.

And then there's Serratia, known for its bright red pigment.

Oh yeah, I've seen that in the lab.

That's prodigyosa, and we're not totally sure what its purpose is, but Serratia marcescens, it can cause infections, especially in hospitals.

Okay, moving right along, we've got Pseudomonadales and Vibrianales, two very common orders within the gamma proteobacteria.

You got it.

Pseudomonas, that's a big and diverse group.

They typically have flagella at their ends and are very good at using a variety of organic compounds for energy.

Pseudomonas aerogenosa, it's a big problem in hospitals.

It can infect all sorts of places, especially in people with immune systems.

It's a master biofilm former, those communities of bacteria that resist antibiotics.

It also has natural resistance to many antibiotics, making it really hard to treat.

In serious cases, doctors sometimes have to use polymixin, which is kind of a last resort antibiotic.

And Pseudomonas syringae is the plant killer, right?

Releasing toxins and enzymes that damage crops.

That's the one.

Different strains are adapted to attack different plants, and they use a variety of weapons like toxins, enzymes that break down plant tissues, and even plant hormones to cause all sorts of damage, from yellow spots to soft rot.

Okay, let's move on to Vibrianales.

They're facultative anaerobes, so they can ferment, and they're oxidase positive, which sets them apart from the enteric bacteria.

Vibrio is the most well -known genus, right?

Absolutely, along with alivibrio and photobacterium, many of which can actually glow in the dark.

They're mostly aquatic, living in the ocean, or estuaries.

Vibrio cholerae is the one that causes cholera, a serious diarrheal disease spread through contaminated water.

Right.

And then you've got Vibrio perihemolyticus, which can cause food poisoning from eating raw or undercooked seafood, especially common in Japan.

It seems their natural home is in marine animals, and we humans are just accidental victims.

Now, we're really making our way through these proteobacteria.

Delta proteobacteria and epsilon proteobacteria are next.

And the force suggests these are smaller classes, maybe not quite as the big three.

That's fair.

Delta proteobacteria, they're known for their sulfate and sulfur -reducing members, like Dysulfovibrio, and you've got Geobacter, which can reduce iron, and even some bacterial predators, like Bellavibrio and Myxococcus.

And don't forget the centrophic bacteria, those that have to team up with other microbes to survive.

Centrophic, it's like a microbial partnership, right?

Exactly.

Centrophobacter wilini, for example, it can only break down a sulfate, but if sulfate is around, it can go solo and even ferment some things on its own.

Pretty flexible.

And epsilon proteobacteria often use the hydrogen sulfide produced by some delta proteobacteria.

The source highlights Campylobacter and Helicobacter, which I know can cause human diseases.

Absolutely.

They're both gram -negative, oxidase, and catalase -positive spiral -shaped, and most are pathogenic.

They prefer environments with low oxygen.

Campylobacter species are a common cause of food poisoning worldwide,

while Helicobacter pylori is famous for causing stomach ulcers.

Good.

Epsilon proteobacteria also includes some real extremophiles that live in places like deep sea hydrothermal vents.

They thrive in high temperatures, get their energy from sulfur compounds or hydrogen gas, and even help some deep sea animals by providing them with food and detoxifying their environment.

And last but not least, in the proteobacteria, we have the metaproteobacteria, which is one known member, Meraprofundus feroxidens, which oxidizes iron in the ocean.

Yep, a specialist for sure.

It contributes to those iron -rich microbial mats on the seafloor.

Okay, we've conquered the proteobacteria.

It's amazing how much diversity there is in just one phylum.

Now, the source moves on to other bacterial groups, focusing on those that are mostly gram -positive,

firmicutes, tinericutes, and actinobacteria.

That's right.

Those four phyla, proteobacteria,

actinobacteria, firmicutes, and bacteridetes.

They make up the vast majority of the bacteria we've been able to study in the lab.

So, let's dive into the firmicutes first.

And within the firmicutes, we've got the lactobacillus, also known as the lactic acid bacteria.

These are the ones that give us yogurt, sauerkraut, all those fermented goodies.

Exactly.

Lactobacillus and streptococcus, those are the stars here.

They ferment sugars without oxygen, producing lactic acid, which gives those foods their tangy taste and helps preserve them.

They don't form spores, are usually negative for oxidase and catalase tests, and don't have the machinery for respiration.

Right.

But they can tolerate oxygen even though they don't use it.

So, lactobacillus, they're usually rod -shaped and are used to make yogurt and sauerkraut, while streptococcus are round and include some nasty pathogens like streptococcus pyogenes, which causes strep throat, and streptococcus mutans, which causes cavities.

The source also mentions leuconostoc, which make those flavor compounds in dairy.

Yep.

And some leuconostoc species can produce those slimy polysaccharides, like dextrin from sucrose.

Streptococcus are also grouped based on how they break down red blood cells on blood agar and based on specific carbohydrates on their surface.

Firmicutes also include non -sporulating bacillus and clostridiales, like listeria, staphylococcus, and sarsina.

They seem like a more diverse group.

They are.

Listeria monocytogenes is a big concern in food safety because it can cause listeriosis and can grow even in the fridge.

Staphylococcus are common on our skin and mucous membranes, but staphylococcus aureus can cause a range of infections.

And then you've got antibiotic -resistant strains like MRSA, which are a real problem.

Sarsina or copcha that form these cube -like clusters.

And sarsina ventriculi can actually live in the highly acidic environment of the stomach and even make cellulose.

And then we've got the sporulating bacillus and clostridiales, the masters of endospore formation like bacillus and clostridium.

Endospores are like those bacterial escape pods, right?

Letting them survive almost anything.

Exactly.

Endospores are incredibly tough, allowing bacteria to survive heat, radiation, chemicals, drying out.

They basically go dormant until conditions improve.

Bacillus species are often aerobic or can grow with or without oxygen.

Some are harmless soil dwellers, but bacillus anthracis causes anthrax.

Some bacillus produce antibiotics and bacillus thuringiensis makes a protein that's toxic to insects useful in agriculture.

Clostridium species are anaerobic, meaning they can't grow with oxygen and they have a wide range of metabolic tricks for breaking down stuff without oxygen.

They're mostly found in soil and the guts of but some cause nasty diseases like botulism, tetanus, and gas gangrene.

And then there's spora sarcina, unique for its round shape and its ability to break down urea.

Okay, onto the tenoricutes with mycoplasma as the main example.

They're weird because they don't have peptoglycan or a cell wall at all.

How do they even function?

It's pretty unusual.

They're like protoplasts, those bacteria that have lost their cell wall, but they're more resistant to bursting than you'd expect.

They have small genomes and are mostly symbionts or pathogens relying on their hosts for survival.

They can have different shapes and their colonies often look like fried eggs on agar plates.

And because they don't have a cell wall, antibiotics that target peptoglycan don't work on them.

They also need special nutrients to grow in the lab.

And within the tenoricutes, spiroplasma are spiral shaped and move using internal fibrils.

They live in ticks, insects, plants, and some cause diseases.

And last but not least, we have the actinobacteria.

The source describes them as filamentous and aerobic, common in soil, and many form those resistant spores, although not as tough as the endospores we talked about.

Right.

Actinobacteria are a big deal in the environment.

Streptomyces, that's a huge genus with over 600 species.

They grow as branching filaments, forming a network kind of like fungi.

They produce spores that can resist drawing out, but they're not as hardcore as endospores.

Streptomyces are mostly in soil and give it that earthy smell.

They like alkaline to neutral soils and produce a ton of enzymes that break down complex stuff.

Okay.

But what they're really famous for is making antibiotics.

It's thought that this might be linked to their sporulation process or maybe as a way to fight off competitors.

Fascinating.

The source also mentions actinomyces, nocardia, coronabacterium, artrobacter, propionabacterium, and mycobacterium.

That's a mouthful.

I know, right?

Actinomyces are also filamentous, but they prefer low or no oxygen and are found in our mouths and mucous membranes.

Nocardia are also filamentous and aerobic, found in soil and water, and some can cause infections.

Coronabacterium are club -shaped and include both animal and plant pathogens, like the one that causes diphtheria.

Arthrobacter are soil bacteria that can switch between rod and round shapes and are very good at surviving tough conditions.

They can even break down herbicides and caffeine.

Wow.

They have a unique way of dividing that makes them look like V -shaped pairs.

Propionabacterium are anaerobic and give Swiss cheese its flavor and texture by fermenting lactate.

And finally, mycobacterium, they're a bit shapeshifting and can branch, but not as extensively as streptomyces.

They're hard to stain because of their waxy cell walls, and some, like mycobacterium tuberculosis, grow very slowly.

M -tuberculosis also needs lipids to grow.

Some mycobacteria produce pigments that can change color depending on light exposure.

Okay, we're in the home stretch.

The source gives a quick overview of some other bacterial phyla, starting with the bacteroides.

Bacteroidates are gram -negative, rod -shaped, and many can glide along surfaces without flagella.

Bacteroids, they're super common in our guts, helping us digest complex carbs.

They're also unusual because they can make sphingolipids, a type of fat found in our tissues.

Cytophaga are aerobic and good at breaking down complex carbohydrates, like cellulose, and some cause fish diseases.

Okay.

Flavobacterioles and sphingovacterioles are other groups.

They can be aerobic or switch it up.

They break down sugars, and many can glide.

They're found in soil and water, and some like it cold.

And then there's the chlamydiae, which I've heard of in the context of human health.

They're those obligate intracellular parasites with the weird life cycle.

And the source says they don't have that FTSC protein that's important for cell division and other bacteria.

Right.

It seems they divide in a different way.

They also often lack a proper cell wall, maybe to hide from our immune system.

They have this two -stage life cycle, switching between a tough, infectious form and a larger replicating form.

They infect a variety of hosts, and some, like chlamydia trachomatis, chlamydoflin ammonia, and chlamydoflis itachi, cause human diseases.

And what about the plankton mycetes and varicomicrobia?

Plankton mycetes live in soil and water, sometimes forming stalks or appendages, and they can even group together.

They're generally not pathogenic, but they have some strange features.

And some can oxidize ammonia without oxygen, which is pretty important.

Varicomicrobia have a warty appearance because of their appendages.

They divide symmetrically, unlike the budding plankton mycetes, and some even have genes for proteins that are usually found in eukaryotic cells.

And finally, the source mentions those heat -loving bacteria, the hyperthermophiles, and other interesting groups like dynacoccus thermus and acidobacteria.

Hyperthermophiles, like Therotoga and Aquifex, live in extremely hot environments, suggesting that early life might have thrived in heat.

Therotoga has a sheath around it and is an anaerobic fermenter.

Interestingly, it seems to have gotten some genes from archaea.

Aquifex includes some of the most heat -tolerant bacteria known, and they get energy from inorganic compounds and use a reverse citric acid cycle to make their food.

Dynacoccus thermus includes dynacoccus radiodurans, which is incredibly resistant to radiation because of its efficient DNA repair and unique DNA arrangement.

And then there's thermus aquaticus, the source of the enzyme that made PCR possible.

Acetobacteria are abundant in soil, but hard to grow in the lab.

Most like acidic environments and get energy from organic compounds.

Other groups include nitrosperry, important in the nitrogen cycle, fusobacteria, found in our guts with some causing diseases,

synergistetes, anaerobic bacteria that break down proteins, deferobactors and chrysiogenetes, anaerobic bacteria with diverse metabolisms, and fibrobacterias, which break down cellulose in guts of herbivores.

Wow, that was an incredible journey through the bacterial world.

From the tiniest to the toughest, the helpful to the harmful, they're an essential part of our planet.

It's clear that they're much more than just germs.

Absolutely.

And what we've covered is just the tip of the iceberg.

When you think about how ancient bacteria are and how they've adapted to survive everywhere, it makes you wonder.

If they can thrive in such extreme environments here, could similar life forms exist on other planets?

That's a fascinating thought to ponder.

Hopefully this deep dive has sparked some new curiosities and given you a new appreciation for these microscopic powerhouses.

Thanks for joining us on the deep dive.