Tuesday, September 21, 2010

Extremophiles

Ok, today’s Nerd Out is all about extremophiles. 

These are organisms that live under what humans deem to be extreme conditions. Perhaps they live in extreme heat, extreme cold, extreme pressure, extreme acidity…or under any other circumstance that would kill an “ordinary” living creature.

You can find extremophiles living in sheets of ice, near vents at the ocean floor, inside of volcanos…perhaps on a meteorite!

I’ll start by talking about my favorite extremophile, Water Bears.

Just look how cute they are! Doesn’t it kind of look like it’s smiling?

These are microscopic organisms with a body length of 1.5 mm. That’s about the thickness of a credit card.

They are called Water Bears because they live in water and they look like bears, duh. They also walk like bears. You know how bears kind of trudge along putting all their feet on the right side forward and then all their feet on the left side forward? That’s what these cuties do.  In fact, their scientific name is Tardigrada, which literally means slow walker.

Also, they have claws! Look:



They can move their claws swiftly the same way a cat does. Maybe they need to defend themselves from tiny microscopic bear hunters?

Water Bears (or tardigrades) are found all over the earth, and the reason is because they can survive pretty much everywhere. They are what’s called a polyextremophile which means they can survive in lots of different kinds of extreme circumstances.

FOR EXAMPLE, they can survive at a temperature of 35 Kelvin. Just to give you some perspective, at 35 K…oxygen is a solid. Oxygen ice. THAT’S COLD.

They can also survive temperatures up to 424 K, or 303 degrees Fahrenheit.

So there’s two extreme conditions under which Tardigrades are able to live. Survival in the hot temperature makes them hyperthermophiles and survival in the cold temperature makes them psychrophiles.

If you are biology-savvy you are probably thinking, “Wait…all living organisms need liquid water. How do Water Bears keep water from freezing or boiling in their cells?”. Many psychrophiles and hyperthermophiles dissolve certain proteins in their bodies to lower the freezing point and raise the boiling point of water. Also, under extreme pressures (like at the bottom of the ocean) the boiling point of water is raised.

Y’all are probably aware of how pressure changes boiling and freezing points…it’s the reason why you can boil water without getting it very hot when you are camping high in the mountains where the air pressure is lower. I’m not sure that this is what keeps water from freezing or boiling the Water Bears’ cells…but it might be! 

I do know this: Water Bears are capable of cryptobiosis. I think this is the same thing as being cryogenically frozen. I’m thinking of Austin Powers. It’s basically this form of preservation where all metabolic processes stop and you are in suspended animation. Water Bears will go into cryptobiosis after being dehydrated and can come back to life 10 years later.  Possibly longer! I don’t know if anyone’s ever tried for longer. Shit, I should find some of these guys, dry em out and check on them again when I’m old.

Ok, so we talked about how they can stand high/low temperatures and dehydration…let’s talk about how they can live in extreme pressures.

Water Bears can survive vacuum. That means no air. Zero pressure. IE: what it’s like in outer space. If humans were to be in the vacuum of space, our blood would boil (cause remember, stuff boils quicker at lower pressures). 

Wired Science listed Tardigrades (Water Bears) as #10 on their list of weirdest things launched into space in 2008. They withstood vacuum AND intense solar radiation then came back to earth in perfect health and were able to produce viable offspring.

They can also survive outstandingly high pressures.  They have been shown to survive in a cryptobiotic state at a pressure of 6,000 atmospheres. To give you a frame of reference, that pressure would definitely crush a submarine.

TARDIGRADES! YOU ARE SO FREAKING COOL!

I like to imagine that tardigrades came to earth from a meteor impact.  I mean, they could survive all the things they would need to in order to stay alive on a meteor. Are they aliens? Maybe these kinds of extremophiles were the seed to all life on earth and we’ve just evolved to be less and less extreme because we don’t need to survive in all those crazy circumstances. Who knows? Not me.

What other kinds of extremophiles are there?

Let’s talk about acidophiles. There are some organisms that prefer to hang out in pools of sulfuric acid. Yeah, sulfuric acid…you know, the stuff that will melt your face? It’s what happened to Two-Face.

Chemists use sulfuric acid as a drying agent because it removes water. In fact, when sulfuric acid reacts with water it releases lots of energy in the form of heat. This is why people get acid burns.

So why aren’t acidophiles getting burned?

They survive by constantly removing hydrogen ions from their bodies at a very high rate. I think that the reason this helps them is because the hydration of sulfuric acid is thermodynamically favorable. That means the sulfuric acid really wants to pick up the hydrogens that H2O has to offer. Maybe the acidophiles eject lots of hydrogen ions as a sort of distracter for the sulfuric acid. Like, “hey don’t take my water…eat this instead!”. I’m not sure, I’m not going to pretend that I know enough chemistry to explain this fully but that seems right to me.

My favorite acidophile is ferroplasma acidarmanus. It’s a microbe that lives in acid and eats iron. Bad. Ass.   

They were discovered by a scientist named Katrina Edwards in the 90s when people were trying to figure out why iron mines were so damaging to the environment.

Here’s the story: sulfide is found naturally in metallic ores. Around iron mines the conversion of sulfide to sulfuric acid is greatly accelerated and no one knew why. This is a problem because it’s not very nice for the environment to have lots of acid run-off from mines. In fact, it has cost mining companies billions of dollars in environmental damage.

So, what’s going on?

As I said earlier, these critters eat iron so they will surely be found in abundance around mines where lots of iron is exposed. Turns out, they are the ones responsible for transforming the sulfide (which is just a negatively charged sulfur ion)  into sulfuric acid. Probably by ejecting all those hydrogen ions. I’ll bet the sulfide picks up 2 of those hydrogens that it’s spitting out and gets four oxygens from the air to make H2SO4. 

So this is a microbe that hates the environment. And eats metal. And lives in acid. It's like a bad guy from Captain Planet.

Ferroplasma acidarmanus forms a green slime. Check it:



The thing that is remarkable about this microbe is that it seems rather fragile. By that I mean, it doesn’t have a cell wall to protect it from the damaging effects of acid. It thrives in acid, it even makes more acid for itself to hang out in, but in all other repsects it's a rather delicate microbe. 

You know where Ferroplasma Acidarmanus would love to live? Jupiter’s moon Europa where there is lots of sulfuric acid frozen on the surface. I’m sure I will nerd out on Europa soon. It’s one of my favorite things to learn about.

Or what about Venus where it rains sulfuric acid? 

Anyway, perhaps you are seeing a pattern? Extremophiles could be the most likely organisms to exist on other planets. I mean, if they can thrive in these kinds of hostile and “unearthly” habitats, why couldn’t they exist in more volatile places in the solar system? 

Tardigrades could certainly live on Mars, at least for a little while. Maybe they already do…

There are lots more extremophiles I could talk about! I didn't even delve into all the ones that live around thermal vents on the ocean floor. Maybe next time! 




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