Berkeley Lab Researchers Identify New Microbial Players in the Global Sulfur Cycle

The Science

Sulfate is ubiquitous in the environment, and sulfate reduction—a key control on anaerobic carbon turnover—impacts a number of other processes such as carbon oxidation and sulfide production. Until now, sulfate reduction was believed to be restricted to organisms from select bacterial and archael phyla. But scientists at University of California, Berkeley, have now found this ability to be more widespread. They used genome-resolved metagenomics to discover roles in sulfur cycling for organisms from 16 microbial phyla not previously associated with this process.

The Impact

Sulfate-reducing bacteria are anaerobic microorganisms essential to sulfur and carbon cycling. Sulfate reduction drives other key processes and produces hydrogen sulfide, an important but potentially toxic gas present in sediments, wetlands, aquifers, the human gut, and the deep sea. The discovery of novel microbes connected to sulfur cycling is relevant in biogeochemistry, ecosystem science, and engineering, and can fundamentally reshape understanding of microbial function and capabilities associated with phylogenetic information.


Phylogenetic information shapes expectations regarding microbial capabilities. In fact, this is the basis of currently used methods that link gene surveys to metabolic predictions of community function. Sulfate reduction, an important anaerobic metabolism, impacts carbon, nitrogen, and hydrogen transformations in numerous environments across the planet and is known to be restricted to organisms from selected bacterial and archaeal phyla. The authors used genome-resolved metagenomic analyses to determine the metabolic potential of microorganisms from six complex marine and terrestrial environments. By analyzing >4,000 genomes, they identified 123 near-complete genomes that encode dissimilatory sulfite reductases involved in sulfate reduction. They discovered roles in sulfur cycling for organisms from 16 microbial phyla not previously known to be associated with this process. Additional findings include some of the earliest-evolved sulfite reductases in bacteria, identification of a novel protein unique to sulfate-reducing bacteria, and a key sulfite reductase gene in putatively symbiotic candidate phyla radiation (CPR) bacteria. This study fundamentally reshapes expectations regarding the roles of a remarkable diversity of organisms in the biogeochemical cycle of sulfur.

Principal Investigator(s)

Susan Hubbard
Lawrence Berkeley National Laboratory


This work was supported by the Office of Biological and Environmental Research within the U.S. Department of Energy Office of Science.


Anantharaman, K. et al. 2018. “Expanded diversity of microbial groups that shape the dissimilatory sulfur cycle.” The ISME Journal. In press (2017). 12, 1715–28 (2018). DOI:10.1038/s41396-018-0078-0.