Microbial transcriptome patterns highlight increased pedogenesis-related activity in arid compared to semiarid soils under 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 transform initial arid and semiarid soils into resilient ecosystems. Additionally, we characterized essential microbial processes and how their gene expression differs between arid and semiarid soils under simulated humid climate conditions. We assessed changes in bacterial and archaeal communities using advanced metagenomic and metatranscriptomic approaches through a sixteen-week climate simulation experiment. The results revealed the triggering of an intense functional response in arid soils compared to semiarid soils under humid climate conditions. Proteobacteria and Actinobacteriota dominated the overall transcriptional profile and specific functions associated with the early stages of soil formation. Arid soils undergo higher transcription of genes linked to soil formation, particularly those associated with soil aggregation, phosphate metabolism, and weathering, potentially promoting the succession of arid soils. Our findings demonstrate the rapid activation of soil formation-related pathways under humid climate conditions, particularly in arid soils, occurring within short timeframes of weeks.