DEEP-SEA MI­CROBES MAY BE MISS­ING LINK IN SEARCH FOR ORI­GIN OF COM­PLEX LIFE

BBC Earth (Asia) - - Update -

Let us in­tro­duce Thor, Loki, Odin and Heim­dall – our mi­cro­bial an­ces­tors dat­ing back two bil­lion years. A team at Upp­sala Univer­sity, Swe­den has dis­cov­ered sev­eral mi­crobes car­ry­ing genes that were pre­vi­ously thought to be unique to more com­plex life forms, in­clud­ing hu­mans.

The sin­gle-celled micro­organ­isms, called ar­chaea, were dis­cov­ered in aquatic sed­i­ments col­lected at seven sites around the world, in­clud­ing hy­dro­ther­mal vents in the Arctic Ocean and hot springs in Yel­low­stone Na­tional Park. The four species in ques­tion, named af­ter Norse gods and known as ‘As­gard ar­chaea’, are as dif­fer­ent from one an­other as a tree is from a mush­room.

The find­ing sup­ports a decades-old the­ory that com­plex life first arose when an ar­chaeon con­sumed a bac­terium, but the bac­terium sur­vived. The re­sult­ing ar­range­ment proved to be ben­e­fi­cial to both, and the two pre­vi­ously sep­a­rate or­gan­isms evolved into life forms with cells and com­plex in­ter­nal struc­tures, called eu­kary­otes. All plants and an­i­mals are eu­kary­otes.

“The things which we thought made a eu­kary­ote a eu­kary­ote, [are what] we’re now find­ing in these new ar­chaea,” said re­searcher Brett Baker. “We’re es­sen­tially rewrit­ing the text­book on ba­sic bi­ol­ogy.”

So far, the ar­chaea have only been iden­ti­fied by piec­ing their genomes to­gether us­ing sep­a­rate bits of gath­ered ge­netic ma­te­rial. The team’s next goal is to grow them in the lab.

“It would be great if we could iso­late or grow As­gard cells, and study them un­der the mi­cro­scope,” said Thijs Et­tema, a re­searcher who was in­volved in the project. “I am con­vinced that this will re­veal more im­por­tant clues about how com­plex cells evolved. Ul­ti­mately, our mi­cro­bial ances­try will be un­cov­ered.”

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