Warmer and drier ecosystems select for smaller bacterial genomes in global soils

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Bacterial genome size reflects bacterial evolutionary processes and metaboliclifestyles, with implications for microbial community assembly and ecosystemfunctions. However, to understand the extent of genome‐mediated microbialresponses to environmental selections, we require studies that observe genomesize distributions along environmental gradients representing differentconditions that soil bacteria normally encounter. In this study, we usedsurface soils collected from 237 sites across the globe and analyzed howenvironmental conditions (e.g., soil carbon and nutrients, aridity, pH, andtemperature) affect soil bacterial occurrences and genome size at thecommunity level using bacterial community profiling. We used a joint speciesdistribution model to quantify the effects of environments on speciesoccurrences and found that aridity was a major regulator of genome sizewith warmer and drier environments selecting bacteria with smaller genomes.Drought‐induced physiological constraints on bacterial growth (e.g., waterscarcity for cell metabolisms) may have led to these correlations. This findingsuggests that increasing cover by warmer and drier ecosystems may result inbacterial genome simplifications by a reduction of genome size.

This study was supported by the Australian ResearchCouncil (DP190103714, DP210102081, and FT190100590).M.D‐B. acknowledges support from the Spanish Ministryof Science and Innovation for the I+D+i project PID2020‐115813RA‐I00 funded by MCIN/AEI/10.13039/501100011033. M.D‐B. is also supported by a project of the FondoEuropeo de Desarrollo Regional (FEDER) and theConsejería de Transformación Económica, Industria,Conocimiento y Universidades of the Junta de Andalucía(FEDER Andalucía 2014‐2020 Objetivo temático“01—Refuerzo de la investigación, el desarrollo tecnológico y lainnovación”) associated with the research project P20_00879 (ANDABIOMA)

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