Resilient Antarctic soil bacteria consume trace gases across wide temperature ranges

Abstract

Polar desert soils host diverse microbial communities despite limited nutrients and frequent temperature and light fluctuations. Adapting to these extremes, most bacteria possess high-affinity hydrogenases and carbon monoxide dehydrogenases, enabling them to use atmospheric trace gases such as hydrogen (H2) and carbon monoxide (CO) to generate energy and fix carbon. Despite the foundational importance of this process in polar desert ecosystems, little is known about the thermal sensitivity of trace gas oxidation or how this process will respond to climate warming. Here, we show through in situ and ex situ incubations that H2 consumption is an exceptionally thermally resilient process that can occur from -20 to +75{degrees}C, at rates comparable to temperate ecosystems (peaking at 8.56 nmol H2 h-1 g dry soil-1 at 25{degrees}C). Temperature ranges of CO (-20 to 42{degrees}C) and CH4 (-20 to 30{degrees}C) oxidation are also wider than expected, though the pattern of thermal sensitivity conforms with general theory. Metagenomic analyses support these data, revealing that atmospheric H2 and CO oxidisers are widespread, diverse, and abundant, and suggesting most Antarctic bacteria function below their temperature optima for these processes. Modelling of seasonal temperatures across ice-free Antarctica under current and future emissions scenarios indicates that H2 and CO oxidation can occur year-round, increasing by up to 35% or 44%, respectively, by 2100. Our results indicate constitutive aerotrophic activity contributing to Antarctic ecosystem functioning and biodiversity across spatial and temporal scales, with further studies required to understand how it interacts with photosynthesis in a changing climate.