Molecular hydrogen in seawater supports growth of diverse marine bacteria.

Molecular hydrogen (H ₂ ) is an abundant and readily accessible energy source in marine systems, but it remains unknown whether marine microbial communities consume this gas. Here we use a suite of approaches to show that marine bacteria consume H ₂ to support growth. Genes for H ₂ -uptake hydrogenases are prevalent in global ocean metagenomes, highly expressed in metatranscriptomes and found across eight bacterial phyla. Capacity for H ₂ oxidation increases with depth and decreases with oxygen concentration, suggesting that H ₂ is important in environments with low primary production. Biogeochemical measurements of tropical, temperate and subantarctic waters, and axenic cultures show that marine microbes consume H ₂ supplied at environmentally relevant concentrations, yielding enough cell-specific power to support growth in bacteria with low energy requirements. Conversely, our results indicate that oxidation of carbon monoxide (CO) primarily supports survival. Altogether, H ₂ is a notable energy source for marine bacteria and may influence oceanic ecology and biogeochemistry.
(© 2023. The Author(s).)