Microbes in the dust: The ecology of arid soil microbiomes

Drylands now cover approximately 45% of Earth's terrestrial surface and are expanding under climate change, yet the microbial communities inhabiting these vast regions remain poorly integrated into ecosystem models. This review synthesizes current knowledge on arid soil microbiomes, revealing that these soils harbor diverse and functionally important microbial assemblages. Water availability acts as a primary environmental filter, triggering a soil “bioreactor” during hydration pulses that drive rapid shifts in community structure and biogeochemical activity. Secondary edaphic filters—low organic carbon, high pH, salinity, and UV exposure—further refine community composition, selecting for specialized taxa with complex survival strategies including dormancy, compatible solute synthesis, sporulation, UV-protective pigmentation, and biofilm formation. These microorganisms contribute to carbon and nitrogen cycling, soil stabilization, and plant productivity through interactions with mycorrhizal fungi and plant growth-promoting rhizobacteria. However, these systems face substantial pressure from climate change—which disrupts pulse dynamics—and land use intensification that degrades fragile biocrusts. Mobilized dust acts as a vector for microbial dispersal, including potential pathogens, across continents. Key knowledge gaps include the lack of long-term in-situ studies, the underexplored role of soil viruses, and the poor integration of microbial processes into global climate models. Understanding these “microbes in the dust” is essential for predicting the fate of expanding drylands and developing strategies for their management and restoration.