diversity of dissimilatory sulfite reductases across several environments. ecological metagenomes

Sulfate-reducing microorganisms (SRM) play important roles in anoxic natural and engineered environments, linking sulfur and carbon cycles. With climate warming, distribution of anoxic habitats propitious to dissimilatory SRM is expanding. Consequently, we hypothesize that novel SRM are likely to emerge from the rare biosphere triggered by environmental change. We analyzed the diversity, community composition and abundance of SRM in 230 samples representing 14 different ecosystems including marine and freshwater ecosystems, oil reservoirs and other engineered infrastructure. Using the dsrAB gene as molecular marker for sulfate-reducing microorganisms, more than 123,000 taxa affiliated to 47 different families were identified. The majority of these can be considered as members of the “rare biosphere”. A third of the dsrAB genes identified, belonged to uncharacterized lineages. The dsrAB sequences exhibited a strong pattern of selection in different ecosystems, and no species or family was ubiquitously detected in all ecosystems. These results expand and biodiversity and distribution of SRM by over 50%, with potential implication for carbon and sulfur cycling in anoxic ecosystems.