Acidobacteria are active and abundant members of diverse atmospheric H2-oxidizing communities detected in temperate soils

Significant rates of atmospheric hydrogen (H-2) consumption have been observed in temperate soils due to the activity of high-affinity enzymes, such as the group 1h [NiFe]-hydrogenase. We designed broadly inclusive primers targeting the large subunit gene (hhyL) of group 1h [NiFe]-hydrogenases for long-read sequencing to explore its taxonomic distribution across soils. This approach revealed a diverse collection of microorganisms harboringhhyL, including previously unknown groups and taxonomically not assignable sequences. Acidobacterial group 1h [NiFe]-hydrogenase genes were abundant and expressed in temperate soils. To support the participation of acidobacteria in H(2)consumption, we studied two representative mesophilic soil acidobacteria, which expressed group 1h [NiFe]-hydrogenases and consumed atmospheric H(2)during carbon starvation. This is the first time mesophilic acidobacteria, which are abundant in ubiquitous temperate soils, have been shown to oxidize H(2)down to below atmospheric concentrations. As this physiology allows bacteria to survive periods of carbon starvation, it could explain the success of soil acidobacteria. With our long-read sequencing approach of group 1h [NiFe]-hydrogenase genes, we show that the ability to oxidize atmospheric levels of H(2)is more widely distributed among soil bacteria than previously recognized and could represent a common mechanism enabling bacteria to persist during periods of carbon deprivation.

Automated summary

The study identified a diverse collection of microorganisms in temperate soils harboring group 1h [NiFe]-hydrogenases, including previously unknown groups and taxonomically not assignable sequences. It discovered that mesophilic acidobacteria can oxidize atmospheric levels of H(2) down to below atmospheric concentrations during carbon starvation, a physiology that may explain their success. The findings suggest that the ability to oxidize atmospheric levels of H(2) is more widely distributed among soil bacteria than previously recognized, potentially enabling bacteria to persist during periods of carbon deprivation.