Metagenomes and metatranscriptomes in arid compared to semiarid soils under simulated humid conditions
In arid and semiarid environments, microbial activity is restricted by limited water and high evapotranspiration, impacting soil formation. Recognizing that this limitation can be overcome under humid conditions, accelerating soil formation by influencing microbial processes, our study aims to investigate which microorganisms help to transform initial soils from arid and semiarid sites into resilient soil ecosystems. We characterized essential microbial processes and how their gene expression differs between soils from arid and semiarid sites under simulated humid climate conditions. We assessed changes in bacterial and archaeal communities using metagenomic and metatranscriptomic approaches through a sixteen-week climate simulation experiment. The results revealed that an intense functional response is triggered under humid climate conditions in the arid site compared to the semiarid site, which showed greater resilience. The arid site undergoes higher transcription of genes associated with soil aggregate formation, phosphate metabolism, and weathering, potentially promoting the development of arid sites. Additionally, a strategic transcriptional reconfiguration linked to soil nutrient dynamics suggests that soil microorganisms use available organic resources alongside autotrophy in response to increased moisture. Proteobacteria and Actinobacteriota dominated the overall transcriptional profile and specific functions associated with the early stages of soil formation in both sites. These findings highlight the rapid activation of pathways related to soil formation under humid conditions in arid sites, potentially associated with their metabolic needs and environmental stress, influencing soil formation dynamics under global climate change.