The Sulfur Cycle as the Gear of the “Clock of Life”: The Point of Convergence Between Geological and Genomic Data in the Cuatro Cienegas Basin

Due to its chemical properties and several stable redox states, microbial transformations of sulfur compounds have been affecting the geochemical features of the Earth’s biosphere since the Archaean. However, despite the great importance of sulfur cycling, reconciling the geologic record with genomic data has been challenging. Here we first review current state-of-the-art evidence about the emergence of life on Earth in sulfur-rich environments, providing a conceptual framework that closely connects these two largely separated disciplines. Then, we summarize the current astonishing diversity of prokaryotes responsible for driving the sulfur cycle, suggesting that, due to their ancient origin, sulfur-associated taxa perhaps hold the greatest diversity of any group of microorganisms to metabolize a single element on Earth. Finally, because the guilds of sulfur metabolizing microbes co-occur at millimeter scales within microbial mats, we use the taxonomic and metabolic information derived from these primordial communities as ecological models to highlight sulfur as the guiding axis of these complex intersections, recapitulating a gear of the clock of life.