The Astronomy Picture of the Day from Sunday was a cool one — a nutrient agar plate of Deinococcus radiodurans, a/k/a “Conan the Bacterium.” (Photo: M. Daly, Uniformed Services University of the Health Sciences.) D. rad is quite the remarkable little microbe — it’s an extremophile, an organism that thrives in conditions that you and I would deem overly harsh. (And no, not the internet.) It even has a listing in the Guinness Book of World Records under “World’s Toughest Bacterium.”
D. rad is able to survive in vacuum and through extremes of temperature as well as dehydration, but its special ability is to shrug off large amounts of radiation: a dosage 3,000 times what would kill a strapping young human. Now, you may perhaps wonder why the Intelligent Designer would bother to equip a certain unicellular organism with such an impressive, but not manifestly adaptive, kind of superpower. It could be that radiation tolerance was quite useful in the environment of the very young Earth, but biologists are also thinking that the radiation resistance may come along with resistance to dehydration (which is something that obviously is useful) — radiation and dehydration seem to cause similar types of DNA damage, and D. rad has a remarkable ability to keep its DNA in good working order. It carries along several copies of its genome, stacked on top of each other, ready to step in at the first sign of damage. It’s like towing an entire repair shop behind your car at all times.
Which means, of course, that we meddling humans want to put it to work. D. rad has already been genetically engineered to clean up spills of toxic mercury, which can be highly radioactive. And now, NASA is exploring the possibility of recruiting the plucky bacteria into the astronaut corps. They are imagining adapting D. rad to help with a variety of tasks that humans might face on a trip to Mars — synthesizing drugs, recycling wastes, producing food, all the way up to terraforming the planet. If I were in charge of this project, I would tread pretty lightly here. These are some tough bacteria — I wouldn’t be surprised if they’re just biding their time until we can fly them to Mars, at which point they’ll rise up and take over both planets.
January 25th, 2006 at 1:04 pm
From the listed qualities (extreme temperature variation, survival in vacuum, dehydration, etc.), it might even have come from Mars in the first place.
January 25th, 2006 at 1:12 pm
yes we survive very well evolution is nice that way personally i find your use of extreme to describe our home rather prejudicial sean we are just tolerant of a wide range of environments the only place we cannot survive is the comments on posts about women in science
January 25th, 2006 at 1:36 pm
Thanks for reminding me of the May 1991 issue of LIFE magazine. It was in that issue that i first read about the plan for terraforming Mars into a resource. D-Rad will be its progenitor? D-Rad as ID??
January 25th, 2006 at 2:46 pm
As it’s a bacterium, it’s likely its ancestor came from Earth, not someplace else, unless the common ancester of archaea and bacteria came from Mars (or elsewhere), eubacteria evolved independently on Earth and Mars, and then some D. radiodurans made the jump to Earth after, say, an impact. Not impossible, but damned unlikely.
I’d be pretty hesitant to introduce it to the Martian surface, myself.
January 25th, 2006 at 4:32 pm
D. radiodurans fouls nuclear reactor primary coolant loops and spent fuel pools, typically surviving 2 MRad acute dose and mostly ignoring integrated doses. 10^7 bacteria/ml at Hanford storage.
Science News 153(21) 325 (1998)
“Something’s Bugging Nuclear Fuel”
http://www.learner.org/channel/courses/biology/units/genom/experts/eisen.html
Lest we get all high and mighty about the brave scout, remember that Serratia marcescens thrives within “sterilized” saline breast implants. Lots of other bugs do too, but this but this bug is brilliant crimson.
Google
“Serratia marcescens” implants 821 hits
January 26th, 2006 at 1:34 am
>I’d be pretty hesitant to introduce it to the Martian surface, myself.
Maybe not to Mars, but I’d like to see it sent to some other planet or asteroid. Not even as a prelude to or part of a human visit, but simply as a seed of life. We talk a lot about populating other planets as a way to preserve the human race, but there’s a decided lack of concern about preserving life in general.
January 26th, 2006 at 11:52 am
I guess I’d worry that we don’t really understand what “life” is very well, because our typical “carbon chauvinism” and “cellular chauvinism”, a direct fuction of having an n of 1 for the existence of “life” in the universe, rather limits our perspective. That’s not to say it isn’t an entirely reasonable perspective, as carbon is the element that allows for the greatest diversity of compounds of the sort we think are needed to build the complex components of living systems, and you’d think that the smallest units of any form of life ought to be somehow discrete from the external environment in some kind of “cell”, for a variety of very practical reasons. Even then, it’s tough to say that water is the only solvent in which living systems could arise, maybe silicon could do the job, and so forth. Maybe we wouldn’t be able to recognize an alien life form even if it was sitting right in front of us. These are some pretty fringe ideas, but we can’t discount them out-of-hand, because we know so little about the nature of exobiology, if it exists at all. So, given that it’s hard to know for certain what an alien ecosystem ought to look like, I’d be hesitant to introduce organisms from our biosphere until we’ve devoted a great deal of study to the matter. D. rad. could be a biome-blasting pathogen if dumped on Ceres for all we really know. I personally consider that possibility remote in the extreme, but who can really say?
January 26th, 2006 at 12:07 pm
Having been exposed to a wide variety of science-fiction disaster scenarios, I’d definitely be reluctant to bring new organisms to other planets unless we were absolutely sure what we were doing. In particular, we would want to avoid doing damage to any existing biological molecules, even if they hadn’t come together to form life. At least, this should be true until we’ve colonized a few hundred different star systems and have planets to waste.
January 26th, 2006 at 2:10 pm
Doesn’t the existence of more extreme forms of life tend to “relax” any anthropic constraints on fundamental parameters making the anthropic principle less predictive. In particular if complex information processing was “discovered” in a non-dna based/non-hydrocarbon environment it would seem to me that the Anthropeople would have some “splaning to do”.
Elliot
January 26th, 2006 at 3:21 pm
I don’t think that even D. rad could survive if, say, the neutron were lighter than the proton, or the vacuum energy were at the Planck scale. But I do agree that many anthropic arguments rely to heavily on extrapolations about our local forms of life.
January 26th, 2006 at 3:32 pm
I didn’t like that APOD very much, because they made the ability to repair DNA sound very exotic. Except for viruses, every organism can repair its DNA. Bacteria, us, and everything in between, can all do it.
Uncle Al: there’s also Pseudomonas aeruginosa, which grows pretty much anywhere, even sterile water containers.
January 26th, 2006 at 8:57 pm
I don’t know that much about D. rad. molecular biology, but there’s repair, and then there’s repair+complete genomic redundancy at all times. When bacteria suffer a lot of DNA damage (as I’m sure D. rad. does in extreme environments), they typically resort to something called an “SOS response”. Repairing double-strand lesions requires replication of DNA, but when damage piles up too quickly for careful error-correction, the SOS response allows for quick-and-dirty replication that sacrifices accuracy for efficiency. If bacteria constantly have to SOS, the mutations will pile up to lethal proportions.
I’m guessling D. rad. can just say “Screw that, I got a handy, carefully synthesized extra copy right here. And a few more where that came from.”
That’s a pretty good trick, to be able to carry around multiple extra genomes for repair whenever you need it, and cope with it all the while. Look at what happens to us when we get even one extra chromosome.
January 26th, 2006 at 10:57 pm
Something I didn’t expect to see at CV! Some loose use of the word “sterile” over here. I think you mean “sterilized”. Lots of things get sterilized, very few things are sterile (in the sense of abiotic). Bacteria are remarkably good at being where they ought not to be (by our standards). BTW, Deinococcus was recently found in the human stomach (a pretty extreme place as wellk, but apparently not as bad as we thought).
January 26th, 2006 at 11:12 pm
P. aeroginosa can even grow in distilled water, but if it was sterilized water, it isn’t aseptic any longer if something is growing in it. Anway, the reason it can grow in distilled water is because even that has some traces of shmutz in it that microbes with very simple nutritional needs can thrive in (sort of). Actually, I think most examples of the genus Pseudomonas (maybe I should use “pseudomonads”) do well in a huge range of conditions, and they’re not picky eaters at all.
February 16th, 2006 at 7:31 pm
For the latest on Deinococcus, see http://www.usuhs.mil/pat/deinococcus/index_20.htm.
Stay tuned for astrobiology-relevant work on radiation-driven microbial ecosystems and how manganese protects proteins, not DNA, during irradiation. Curious about what all of you are being taught on why ionizing radiation kills cells.
Mike
February 17th, 2006 at 12:38 am
Probability 1, by Amir D. Aczel, page 99,
Well?
February 21st, 2006 at 12:12 am
The debate about ALH84001 continues, but scientific consensus after a decade does not support the original paper published by McKay. That said, the decision by Science to publish the report was good since it forced the community to think carefully about the topic of biosignatures and what to look for in the future. Unfortunately, a Mars sample return mission seems very far away.
May 11th, 2006 at 4:59 am
Anybody knows what time need Deinococcus for have their mitosis? and what type of grow table it have?
I’m a student of Biotechnology and I needed for a work.