부산대학교 도서관

Chemolithoautotrophic nitrite-oxidising bacteria (NOB) of the genus Nitrospiracontribute to nitrification in diverse natural environments and engineered systems. Nitrospiraare thought to be well-adapted to substrate limitation owing to their high affinity for nitrite and capacity to use alternative energy sources. Here, we demonstrate that the canonical nitrite oxidiser Nitrospira moscoviensisoxidises hydrogen (H2) below atmospheric levels using a high-affinity group 2a nickel-iron hydrogenase [Km(app)= 32?nM]. Atmospheric H2oxidation occurred under both nitrite-replete and nitrite-deplete conditions, suggesting low-potential electrons derived from H2oxidation promote nitrite-dependent growth and enable survival during nitrite limitation. Proteomic analyses confirmed the hydrogenase was abundant under both conditions and indicated extensive metabolic changes occur to reduce energy expenditure and growth under nitrite-deplete conditions. Thermodynamic modelling revealed that H2oxidation theoretically generates higher power yield than nitrite oxidation at low substrate concentrations and significantly contributes to growth at elevated nitrite concentrations. Collectively, this study suggests atmospheric H2oxidation enhances the growth and survival of NOB amid variability of nitrite supply, extends the phenomenon of atmospheric H2oxidation to an eighth phylum (Nitrospirota), and reveals unexpected new links between the global hydrogen and nitrogen cycles. Long classified as obligate nitrite oxidisers, our findings suggest H2may primarily support growth and survival of certain NOB in natural environments.