Extremophilephile: loving the unlovable


Extremophile describes organisms that “love” extremes, thriving in environments that would kill most cellular life. Extremophiles are so varied it’s hard to do this category of life justice in a blog post, so here’s just a sprinkling of some of those that catch my eye.

Life is… well, what adjective could accurately describe the versatility and diversity of life on Earth? Remarkable? Astounding? Incredible? Each of these superlatives pales in comparison to the wonder that is biology.

Life never ceases to surprise.

The discovery of Halicephalobus mephisto, a nematode ‘worm from hell,’ which thrives over two miles beneath the ground, has rewritten the textbooks on the bands within which live can evolve, raising hopes that such a subterranean migration could occur elsewhere on places like Mars or Enceladus.

As [insert superlative here] as mephisto is, the bacteria on which this worm feeds are even more [insert an even stronger superlative here].

Recognized as a species of Firmicutes, this bacteria thrives on molecules produced as a byproduct of the radiation given off by naturally decaying Uranium breaking up water into peroxide. This means that like the bacteria around deep sea thermal vents, these Firmicutes exist independent of the rest of the biosphere.

These Firmicutes have carved out their own ecological niche entirely separate from photosynthesis-driven surface life. If life on Earth was wiped out by radiation from a nearby supernova or a massive asteroid impact, these little critters probably wouldn’t notice.

Nematodes tend to rate highly on any list of extremophiles because they have adapted to living anywhere from the Antarctic to the deserts of North Africa. When winter closes in on Antartica, these guys do what guys do everywhere when the winter snows start looming, they put some antifreeze in the radiator. Only these guys incorporate antifreeze (glycerol) in their blood.

And this party trick isn’t reserved for microscopic creatures, the Antarctic ice fish does the same thing.

Tardigrades, or water bears, are a personal favorite, as these guys are complex creatures capable of being revived after spending a week in outer space, exposed to the harsh vacuum and solar radiation in a low Earth orbit.

Not only that, but tardigrades can be found in the Himalayas, at 20,000 ft above sea level, as well as down to 13,000 ft below the ocean. Tardigrades are exceptional in that they thrive in all extremes, not just in one niche area. They’ve been revived from temperatures as low as almost absolute zero, and can survive at upwards of 300F or 150C.

Like all extremophiles, tardigrades raise the prospect of life potentially existing elsewhere within the extremes of the solar system.

Deinococcus radiodurans is a bacterium that can survive a thousand times the radiation levels that would kill a human. Scale that up to three thousand times a lethal dose for us, and the survival rate is still over 37% for a given culture of radiodurans. Given how quickly bacteria multiply, this would barely phase the organism.

The surprising thing about radiodurans is that there’s nowhere on Earth that’s naturally exposed to these kind of radiation levels. These are the kinds of radiation levels we see around Jupiter, and that bacteria from the relatively benign third-planet out from the sun could thrive on a Jovian moon bathed in harsh radiation is astounding. In this regard, Io, Ganymede or Europa are suddenly looking quite promising in the hunt for extraterrestrial life.

Speaking of harsh environments, there are bacteria that can survive in hydrochloric acid (ph 1.5-3.5) in the human gut.

There’s even been bacteria revived from ice cores dated at over a hundred thousand years in age, highlighting how hardy microscopic life is in contrast to macroscopic life.

The dry valleys of Antartica, the driest place on Earth, offer a glimpse of the kind of life that could be possible on Mars. There’s little or no ice present in these frozen deserts, while what minuscule rainfall occurs on an annual basis freezes or evaporates within a day.

With mean temperatures around -35C (-90F), the only significant difference between Antartica and the highlands of Mars is the atmospheric composition and pressure. Fungi and bacteria exist within a few centimeters of the surface. With no appreciable water, they form a thin, dry crust, defying all expectations as to what is required for life to thrive.

Even apparent “dead zones” on Earth, ocean and lakes starved of oxygen, have evolved anaerobic bacteria.

The more we look, the more we find life carving out an existence in the harshest environments on Earth.

Given the mechanisms by which Natural Selection drives evolution, and the advantages of specialization in dominating an environmental niche, all this shouldn’t be surprising, but it is carried to an extreme beyond anything we could have imagined, and that bodes well in the search for extraterrestrial life. As nice as it would be to find intelligent aliens, I’d settle for microscopic extraterrestrial life in the first instance, as we would learn so much from such a discovery.

It’s impossible to predict how successful SETI will be in searching for intelligent alien life, and the search for extraterrestrial life within the solar system might not find anything, and yet it may be that given the success of bacteria on Earth, both in terms of longevity, diversity and their tolerance of extremes, that we could find alien microbial life before we hear from ET.

Instead of looking completely implausible, our knowledge of extremophiles on Earth helps us to understand that life elsewhere within our solar system is plausible. I guess that makes NASA scientists extremophilephiles, as they love those organisms that love extremes.

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14 thoughts on “Extremophilephile: loving the unlovable

  1. We’ll definitely find microscopic life long before we find aliens speaking through technology we can detect. ;)

    What an awesome post, Peter! You’ve gotta know how exciting these little critters are to me, right? Life is so wonderfully resilient — not just animal or plant life — that it’s hard to believe in a sterile universe.

    Thank you for this post.

    • If there’s life on Mars or if there’s ever been life on Mars, Curiosity should find evidence for it in Gale Crater… and given what we know about extremophiles, I’m hopeful… Glad you enjoyed the post. I figured you were an extremophilephile :)

    • We’ll definitely find microscopic life long before we find aliens speaking through technology we can detect.

      That’s what I think, too.

      Thanks for this roundup of extremophiles. Very interesting reading.

      • LIfe on Earth is surprisingly tenacious and resilient, if the same is true elsewhere then life will be able to survive in the extremes of Mars, Enceladus, etc, which is an exciting prospect. Thanks for dropping by.

    • Yes, it is certainly adept at finding ways we never dreamed of on Earth. Mars is a long shot at life, as it is physically quite small, but if life has thrived there then the implications for the rest of the galaxy/universe are quite profound.

  2. Wonderful post indeed… Nature always manages to amaze us… (:-). By the way, did you hear about Craig Venter’s new project? He essentially wants to send a ship to Mars with a DNA sequencer, possibly get genomes from Martian organisms and radio the sequences to earth so he can synthesize them. Pretty out there and he is asumming a lot, first and foremost that life on Mars will be DNA-based. However, he’s been right more times that he has been wrong. Of anyone can make this happen, it’s him… Talk about interesting times!!!!

    • WOW… that is some serious technology to operate at a distance of anywhere from 50 million to 400 million miles, but I’d love to see him pull it off. Searching Mars for samples would be a bit of a challenge, but there appear to be plenty of subsurface aquifers breaking through the side of craters at a distance of 10-20 meters below the surface. That would be the sweet spot. Eventually, Curiosity will examine some of these in Gale Crater, which will be fascinating and may prompt future missions like the one he’s proposing. Exciting times, indeed.

  3. As an organic chemist, science writer (and sci-fi author) I’d say in response to your initial ponderings about life that – Life is the toughest fragile thing there is. Individual organisms are so fragile, but the phenomenon of life is incredibly resilient and tough. So it’s not exactly that extremophiles “love” extremes, it’s just that if it is possible for life to live somewhere – anywhere – it will find a way. Life is driven to explore the extremities by the things that are already established in the comfort zones.

    • Good point. Life has stepped gingerly into extreme environments over millions of years, a point that might mean reaching those extremes on other worlds is not as easy as it might seem.

  4. One thing that is easy to forget is that the label “extremophile” is based on what we humans consider extreme environments. To them, those environments are not only normal, they are optimal…

  5. Extremophiles are the most interesting organisms on Earth because they can exist anywhere there’s energy! They really push the definition of life as we know it, and put the feats and pressures of human existence to scale.

    There are also organisms that push genetic limits. Check out this article about a genetic extremophile, a bacterium that survives on a genome of 182 genes:

    http://www.nature.com/news/2006/061009/full/news061009-10.html

    It has the world’s smallest genome and must parasitize insects to live!

    • That is very cool… I didn’t note this in the blog post, as it was already quite a lengthy post, but the bacteria surviving in the cold, dry deserts of antartica is from a species that is normally found thriving on insects, confirming that (a) once Antartica was hospitable and (b) bacteria are astoundingly resilient and versatile, clinging on to life in spite of severe environmental changes and the loss of a host. Quite remarkable, really, and raises the possibility of life scratching out an existence on Mars or Enceladus.

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