Virtually all oxygen on Earth was and is produced by photosynthesis, which was invented by tiny organisms, the cyanobacteria, when our planet was still a rather uninhabitable place. Cyanobacteria evolved more than 2.4 billion years ago, as stromatolites – fossilized microbial mats – show, but it took almost 2 billion years until Earth transformed to the oxygen-rich planet we know today.

“We do not fully understand why it took so long and what factors controlled Earth’s oxygenation,“ said geomicrobiologist Judith Klatt in a statement published by the Max-Planck-Gesellschaft in Berlin. “But when studying mats of cyanobacteria in the Middle Island Sinkhole in Lake Huron in Michigan, which live under conditions resembling early Earth, I had an idea.”

Klatt worked together with a team of researchers around Greg Dick from the University of Michigan to study the microbes and cyanobacteria community colonizing groundwater inflows on the bottom of Lake Huron, where the oxygen levels are very low.

“Life on the lake bottom is mainly microbial, and serves as a working analog for the conditions that prevailed on our planet for billions of years”, says Bopi Biddanda, a collaborating microbial ecologist from the Grand Valley State University. “The microbes there are mainly purple oxygen-producing cyanobacteria that compete with white sulfur-oxidizing bacteria. The former generate energy with sunlight, the latter with the help of sulfur.”

source: http://www.forbes.com / Forbes.com / Home> Science / by David Bressan, Contributor / August 02nd, 2021