De Profundis…

by Elio

We are fond of posting “Talmudic Questions,” questions we consider to be more interesting than their answers. The very first of them, dated December 1, 2006, reads as follows:

Where on Earth would one expect to find a single species of microbes (a pure culture) for sustained periods of time? Symbioses (mutualistic or parasitic) do not count, neither do Petri dishes.”

Scanning electron micrograph of a sample from a
different mine, a mere 648 meters down, where D.
audaxviator is also the predominant organism. The
tiny globular objects are presumably silicates, which
have been found to precipitate upon cooling after
sample collection. Source

It turns out there is now a candidate (actually, a Candidatus) nominated for this lonesome role. It is a bacterium, named Candidatus Desulforudis audaxviator, found in the ground water of a South African gold mine, 2.8 km below the surface. Here, in this challenging locale, D. audaxviator accounts for at least 99.9% of all living things (with the remaining fraction thought to be trace contaminants from the mine or lab). A fair amount is known about it, even though it has yet to be cultured. It is a Gram-positive obligate anaerobe, a member of the Firmicutes and somewhat related to the Clostridia. Home is warm and alkaline—around 60 °C and pH 9.3. Its fully sequenced genome tells us that it is probably motile and a sporeformer, and that it makes its living from oxidizing hydrogen using sulfate as the electron acceptor. Both of those substances are relatively abundant in its habitat. Its hydrogen "fuel" is probably formed as a by-product of the radioactive decay of uranium within the earth. Thus D. audaxviator carries the banner for Life Without Sunlight to new depths.

However, this is not life at it’s fullest.

The biomass of D. audaxviator is not overwhelming. By flow cytometry, the authors determined a modest population of about 3.3 x 10⁴ cells/ml in the water of this aquifer. In addition, their best guess is that foodstuff is so limiting that the generation time of these organisms may be reckoned in the hundreds, if not thousands, of years. This is not life in the fast lane. But not having competitors allows for a leisurely existence.

Deep gold mines are great places to set up a geomicrobiological laboratory—if you can stand the heat. But, think of the advantages of not having to drill down those thousands of meters from the surface. It bears noting that this report is based on a lot of work, involving 20 researchers, and with it comes a colossal amount of supplementary data.

The name of the organism tells its story. It stems from Jules Verne's Journey to the Center of the Earth, where the explorers find a secret inscription: Descende, audax viator, et terrestre centrum attinges (Descend, bold traveler, and you will reach the center of the earth).

Comments

I think I answered Mark's question once before in this forum. Human and other animal bladders are generally sterile.

stan zahler

[Elio Schaechter]

Thanks, Jim, for pointing this out.

The whole quote from Verne is:

"In Sneffels Joculis craterem quem delibat
Umbra Scartaris Julii intra calendas descende,
Audax viator, et terrestre centrum attinges.
Quod feci, Arne Saknussemm.

Which bad Latin may be translated thus:

"Descend, bold traveller, into the crater of the jokul of Sneffels, which the shadow of
Scartaris touches before the kalends of July, and you will attain the centre of the
earth; which I have done, Arne Saknussemm."

Interesting that Verne seems to have used bad Latin on purpose.

To give the flavor of is, writing, this is what follows the quote above:

"In reading this, my uncle gave a spring as if he had touched a Leyden jar. His audacity, his joy, and his convictions were magnificent to behold. He came and he went; he seized his head between both his hands; he pushed the chairs out of their places, he piled up his books; incredible as it may seem, he rattled his precious nodules of flints together; he sent a kick here, a thump there. At last his nerves calmed down, and like a man exhausted by too lavish an expenditure of vital power, he sank back exhausted into his armchair"

[Jim Harrison]

The "Descende, audax viator" line is in dactylic hexameter, the same meter as the epics of Virgil and Homer. School kids used to be taught how to compose hexameter lines in Latin so it wouldn't be odd if Verne cooked it up. I don't think it is a quotation.

[Mark O. Martin]

Fast, but not fast enough!

[Elio Schaechter]

Well, Mark, for a change we beat you to the punch. See Talmudic Question # 8 at
http://schaechter.asmblog.org/schaechter/2007/03/talmudic_questi.html

Great minds think alike!

Elio

[Mark O. Martin]

Thus, Elio, I retract my earlier comment. Microbiologically rephrased John Donne was NOT correct:

"No (microbial species) is an island entire of itself..."

Slow, lonely, and tenacious. And looking at the recent NASA photographs of Enceladus, complete with jets of water containing what appear to be organic compounds, I keep wondering if microbiological life blooms elsewhere in our solar system.

Which brings me to a possible new Talmudic Question: is there any environment on Earth with liquid water that does NOT contain a microbial population?