New paper: New study traces the evolution of microbial sulfur oxidation metabolism through Earth’s oxygenation history

Microbial sulfur oxidation plays a central role in Earth's biogeochemical cycles by converting reduced sulfur compounds back into sulfate while linking the sulfur cycle to the cycling of carbon, nitrogen, oxygen, and iron and manganese minerals. Although these microbial processes have shaped our planet for billions of years, how the underlying sulfur oxidation pathways evolved has remained largely unknown.

Tomohisa Sebastian Tanabe and Alexander Loy contributed to a new study led by Song-Can Chen at Zhejiang University that reconstructed the evolutionary history of the Sox sulfur oxidation system, a multi-enzyme complex central to Earth's oxidative sulfur cycle. By analysing more than 85,000 bacterial and archaeal genomes together with 8.7 million viral genomes, the international team showed that an ancestral version of the Sox pathway evolved at least 600 million years before the Great Oxidation Event, approximately 2.35 billion years ago, when oxygen first began to accumulate in Earth's atmosphere. As oxygen levels rose, the pathway acquired additional components that enabled microorganisms to use oxygen more efficiently, driving the diversification of sulfur-oxidizing microbes and their gene exchange with viruses that continue to shape ecosystems today.

The findings provide a compelling example of the co-evolution of microbial life and Earth's changing environment. They reveal how innovations in microbial metabolism accompanied, and likely influenced, major transitions in Earth's oxygenation, highlighting the profound role of microorganisms in shaping the chemistry of our planet over billions of years.