Community coalescence altered the potential of horizontal gene transfers within the native soil microbiome

Microbial community coalescence, which refers to the mixing of microbial communities, frequently shapes the assemblage of soil microbiomes in natural ecosystems. It can exert selective pressure on the coalescent taxa, leading to ecological changes in microbial community structure or microbial evolutionary changes via horizontal gene transfer (HGT). However, the influence of community coalescence on the potential of HGTs within native communities, particularly in soil ecosystems, remains poorly understood. Here, we experimentally quantified the potential evolutionary consequences of soil coalescence. We achieved that by subjecting microcosms containing natural soil to invasion by several microbial communities and profiling mobile genetic elements (MGEs) and adaptive genes of microbial communities up to 60 days after coalescence. Our findings revealed both specific and common responses of MGEs to coalescences over time. Specific effects differed across invasive communities and were particularly pronounced in the early stages. Common effects were associated with an increased abundance of insertion sequences (ISs) across different treatments, suggesting that ISs played a crucial role in promoting diversification at the community level. In summary, we showed that changing MGE profiles are an intrinsic response of the soil microbial community to coalescence-imposed pressure. Our study provides new insights into the modulation of adaptability in soil microbial communities by utilizing community coalescences to address global challenges.