Here\u2019s what you\u2019ll learn when you read this story:<\/p>\n
The Great Oxygenation Event marked a massive transition in life on Earth, when oxygen became plentiful and organisms suddenly had to adapt.<\/p>\n
Current conditions in Japanese hot springs give clues as to how some of these ancient microorganisms survived and adapted to such a drastic change in their environment.<\/p>\n
Understanding ancient life on Earth could lead to finding the start of life on other planets.<\/p>\n
In Earth\u2019s earliest days, oxygen levels were on the order of a million times lower than they are now. The spike in oxygen known as the Great Oxygenation Event (which occurred around 2.3 billion years ago) eventually allowed vegetation and animal life to evolve, but the transition required huge shifts in chemical processing from the organisms already evolved to create energy in what was basically an entirely different atmosphere. So, how did early Earthlings survive while this titanic change was underway?<\/p>\n
To find out, a group of researchers studied five iron-rich hot springs in Japan that they wrote are \u201cpotentially providing windows into ancient microbial ecology,\u201d in a study published<\/a> in the journal Microbes and Environment. These hot springs<\/a> could provide all sorts of clues to understanding both ancient microorganisms and potential life on other planets, as they closely mimic the conditions that would have dominated ancient oceanic environments during the Great Oxygenation Event.<\/p>\n \u201cThese iron-rich hot springs provide a unique natural laboratory to study microbial metabolism under early Earth-like conditions during the late Archean to early Proterozoic transition, marked by the Great Oxidation Event,\u201d Shawn McGlynn, a study author, said in a statement<\/a>. \u201cThey help us understand how primitive microbial ecosystems may have been structured before the rise of plants, animals, or significant atmospheric oxygen.\u201d<\/p>\n What makes these springs so special is that they are naturally rich in ferrous iron, something rare on today\u2019s Earth. They also have low levels of oxygen<\/a> and a near-neutral pH\u2014conditions that the team believes match the environment of much of Earth\u2019s oceans around the time of the oxygen shift. The researchers from the Earth-Life Science Institute and the Institute of Science Tokyo believe that iron-rich ecosystems are what helped keep the microorganisms that did make it through this global chemical shift alive.<\/p>\n The team found iron-oxidizing bacteria to be the dominant microbes in four of the five hot springs they analyzed. The organisms were thriving in low-oxygen conditions using ferrous iron as its main energy source, while cyanobacteria\u2014known for producing oxygen through photosynthesis (and likely being some of the first on Earth<\/a> to do so)\u2014were present in relatively small numbers. The fifth hot spring, though, provided an anomaly, where non-iron-based metabolisms were dominant.<\/p>\n The team analyzed the functions of over 200 high-quality microbial genomes from the hot spring community. \u201cDespite differences in geochemistry and microbial composition across sites,\u201d Fatima Li-Hau, study co-author, said in a statement, \u201cour results show that in the presence of ferrous iron and limited oxygen, communities of microaerophilic iron oxidizers, oxygenic phototrophs, and anaerobes consistently coexist and sustain remarkably similar and complete biogeochemical cycles.\u201d These cycles include carbon<\/a> and nitrogen<\/a> cycles, as well as partial sulfur cycles.<\/p>\n