‘Follow the Water’: Microbial Water Acquisition in Desert Soils

Water availability is the dominant driver of microbial community structure and functionin desert soils. However, these habitats typically only receive very infrequent large-scale waterinputs (e.g., from precipitation and/or run-off). In light of recent studies, the paradigm that desertsoil microorganisms are largely dormant under xeric conditions is questionable. Gene expressionprofiling of microbial communities in desert soils suggests that many microbial taxa retain somemetabolic functionality, even under severely xeric conditions. It, therefore, follows that other, lessobvious sources of water may sustain the microbial cellular and community functionality in desertsoil niches. Such sources include a range of precipitation and condensation processes, includingrainfall, snow, dew, fog, and nocturnal distillation, all of which may vary quantitatively dependingon the location and geomorphological characteristics of the desert ecosystem. Other more obscuresources of bioavailable water may include groundwater-derived water vapour, hydrated minerals,and metabolic hydro-genesis. Here, we explore the possible sources of bioavailable water in thecontext of microbial survival and function in xeric desert soils. With global climate change projectedto have profound effects on both hot and cold deserts, we also explore the potential impacts ofclimate-induced changes in water availability on soil microbiomes in these extreme environments.