Researchers supported by the NASA Exobiology and Evolutionary Biology program have provided new information about the ‘diet’ of microorganisms on the early Earth. By studying 3.45-billion-year-old rocks in Australia’s Strelley Pool Formation, the team has uncovered clues about ancient microbial sulfur metabolism.

“Our results do not prove that sulfate-respiring microbes produced the stromatolitic laminations—they just indicate that sulfate-respiring microbes were present within the microbial mat,” explains lead author Tomaso R. R. Bontognali. “This finding highlights important similarities between these early ecosystems and their modern counterparts.

Their paper, “Sulfur isotopes of organic matter preserved in 3.45-billion-year-old stromatolites reveal microbial metabolism,” was published in the Proceedings of the National Academy of Sciences (PNAS).