Breathar­ian bac­te­ria dis­cov­ered in Antarc­tica

The world-first dis­cov­ery opens new pos­si­bil­i­ties for ET.

Cosmos - - Digest -

Bac­te­ria in the frozen wastes of Antarc­tica can sur­vive on air alone.

Rather than re­ly­ing on sources that power other life on Earth – pho­to­syn­the­sis, sugar, geo­ther­mal en­ergy – they split hy­dro­gen for en­ergy and fix car­bon from car­bon diox­ide and car­bon monox­ide.

The world-first dis­cov­ery that bac­te­ria are ca­pa­ble of such a feat was re­ported in Na­ture by a team of Aus­tralian and New Zealand re­searchers.

The find­ing “opens up the pos­si­bil­ity of at­mo­spheric gases sup­port­ing life on other plan­ets”, says team mem­ber mi­cro­bi­ol­o­gist Belinda Fer­rari of the Univer­sity of NSW.

The Antarc­tic’s in­te­rior ‘deserts’ are the most bar­ren on Earth. Zero veg­e­ta­tion, pro­longed pe­ri­ods of dark­ness or sear­ing ul­travi­o­let ra­di­a­tion, and cy­cles of freez­ing and thaw­ing that can rot the very stones, make the deserts par­tic­u­larly in­clement lo­ca­tions for life.

Sci­en­tists have known since 2000, by test­ing for DNA frag­ments, that mi­cro­bial com­mu­ni­ties some­how sur­vive in the soil. “But how was a mys­tery,” says Fer­rari.

This time round Fer­rari and her col­leagues used metage­nomic tech­niques to put those DNA frag­ments to­gether and dis­cover their ge­netic se­crets. They col­lected DNA from two eastern Antarc­tic sites: one near Casey Sta­tion in Wilkes Land and the other a few hun­dred kilo­me­tres from Davis Sta­tion in Princess El­iz­a­beth Land.

The DNA frag­ments were pieced to­gether like a jigsaw puzzle to re­veal the near-com­plete genomes of 23 in­di­vid­ual mi­cro­bial species, in­clud­ing Acine­to­bac­ter as well as two pre­vi­ously un­known bac­te­rial phyla, named WPS2 and AD3.

By peer­ing at the in­di­vid­ual genes of these newly iden­ti­fied bac­te­ria, the re­searchers found two big clues that they had stum­bled onto a new form of life chem­istry dubbed ‘trace gas car­bon fix­a­tion’.

One was a gene for an en­zyme called high affin­ity hy­dro­ge­nase. It is ca­pa­ble of pulling in trace amounts of hy­dro­gen from the at­mos­phere and split­ting the mol­e­cule to pro­duce en­ergy.

The other was a set of genes for a weird form of Ru­bisco – an en­zyme com­plex usu­ally in­volved in pho­to­syn­the­sis.

But not here: the weird Ru­bisco used hy­dro­gen power to drive car­bon fix­a­tion. The car­bon was sucked in by en­zymes that bind trace amounts of car­bon diox­ide and car­bon monox­ide, fix­ing them into car­bon com­pounds.

Fer­rari notes they did not de­tect any genes for true pho­to­syn­the­sis so trace gas car­bon fix­a­tion is the main game for this ex­treme com­mu­nity.

“It looks like a process ca­pa­ble of feed­ing a whole web of life,” he says.

CREDIT: BSIP / GETTY IM­AGES

Bac­te­rial species in Antarc­tica can split hy­dro­gen for en­ergy. Some be­long to the Acine­to­bac­ter fam­ily shown here.

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