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fossil of what may be the oldest sulfur - feed bacteria ever discover have been chance on in rock date back a staggering 2.52 billion years .
The fossil do n’t represent theoldest lifeon Earth by any stint — there are fossils of microbes that areat least a billion class older — but they are the one-time of their type . They also illuminate a mysterious stage of geologic history , when there was hardly any oxygen in the air andphotosynthesis — the process that would finally oxygenate the standard atmosphere — had just evolved , said field loss leader Andrew Czaja , a geologist at the University of Cincinnati .
University of Cincinnati geologist Andrew Czaja points to a section of black chert in Northern Cape province, South Africa, where microscopic fossils that may be the oldest known sulfur oxidizers were found. The bacteria lived 2.52 billion years ago.
Rather than using atomic number 8 to pull through , these bacteria would have turn hydrogen sulfide into sulfate ( the oxidized form of sulfur ) , using the vigour from that chemical response to farm , Czaja said .
" There ’s still a lot we do n’t know about the former story of Earth , " simply because few fogey - containing sway still survive from that clip , Czaja told Live Science . And yet the epoch between 3.5 billion and 2.5 billion years ago was all-important for life on the major planet .
" Everything was evolving ; all these different bacterial metabolisms were develop , " Czaja said . [ 7 Wild Theories on the Origin of Life ]
Deep dive
But until now , most of what researchers know about this eon , called the Archean , has been based on a handful of fogy from shallow - water environments . Czaja and his colleagues desire to do it what might have been lurking in much deep section of the sea . They hunt for dodo in two areas of South Africa ’s Northern Cape state , looking for signs of ancient life in the Gamohaan Formation . A section of rock call black chert in this geological formation formed from sediment in the deep sea , Czaja tell , probably at least 300 feet ( 100 meters ) down .
" It ’s only one of a couple places you could go " to find rocks so old , Czaja suppose .
The researchers accumulate sample distribution and brought them to the lab , where they slit them into slight , varnished - glass - like sectionsthat could be examined under a light microscope . Immediately upon looking at the section , Czaja noticed elliptic structure , wrinkled like part deflated beach orchis , embedded in the chert .
" As soon as I saw them in the rock , I thought , ' That looks biological , ' " he said .
A geochemical analysis reveal that the structures were made oforganic carbon , a hallmark of fossilized life . But the cells were about 100 to 200 micron in diam , too big to be cyanobacteria , the type of ocean - inhabit bacteria that use photosynthesis to exist . ( A micrometer is one - millionth of a metre ; a human haircloth has a diameter of about 50 micron . ) Czaja consider that the cells might be eucaryotic plankton , or plankton with cell walls , but the bacteria lack the molecular structures seen on the surface of these organisms . What they resemble most was sulfur - oxidate bacteria that live in rich ocean sediments today , Czaja found .
A pre-oxygen ecosystem
Other ancient sulfur eaters have been establish , Czaja say , but they were a few hundred million eld young and forge like stringy filaments . This is the first grounds of spherically shaped sulphur oxidizers , he say .
If the identification is right-hand , the smooshed little spheres might fill in an bionomic gap , Czaja articulate . The chemistry of rock from this time menstruum have suggest that for at least 3.5 billion years of story , being that foreshorten sulfate into hydrogen sulphide have exist on Earth . These bacteria deform sulfate into atomic number 1 sulphide for capture and rein the vim from the reaction .
But there was very footling oxygen in the atmosphere to make oxidize sulfur before about 2.3 billion years ago , when photosynthetic organisms for good altered the air with their oxygen emissions . The freshly learn sulfur oxidizers could be a source of the oxidized sulfur that sulfate reducers of the earned run average needed for fuel , Czaja said .
" These organisms that I get a line could potentially help close that loop-the-loop by being the organism that take reduced S and exchange it to oxidized sulphur , " he said .
Inmodern - day deep sea deposit , bacterium do just that , he added : Sulfur - oxidizing bacterium often dwell right on top of sulfur - reduce bacteria in the sediments , and the two recycle each other ’s permissive waste products .
Czaja and his colleagues plan to further analyse the chemistry of the fossils to find out more about their metabolism .
" I want to get back to South Africa and sample to seek for more , " Czaja say .
The researchersreported their findingsin the December return of the journal Geology .
Original clause onLive Science .
