Antibiotic sensitivity as a key Determinant: B. Subtilis Reshapes the Microecology to mitigate antibiotic resistance...

This study aimed to investigate the role of inoculant antibiotic susceptibility in controlling antibiotic resistance genes (ARGs) during aerobic composting. A systematic comparison was conducted using Bacillus subtilis strains (sensitive, S; resistant, R) to assess ARG dynamics, microbial community evolution, and the underlying ecological mechanisms. Results demonstrated that the sensitive strain significantly enhanced composting efficiency, achieving a higher and longer-lasting secondary thermophilic phase (58.4°C for 4 days) and superior maturity indices compared to the resistant strain. Crucially, the R strain counteracted the ARG-removal effect of high temperatures, increasing total ARG abundance by 28.40% by day 6 and resulting in a final ARG burden 2.74 times higher than the S treatment.Microecological mechanism analysis revealed that the sensitive strain fostered a specialized, modular microbial network with reduced niche breadth, enhancing community stability and functioning as a genetic firewall to restrict ARG dissemination. In contrast, the resistant strain created a fragile, hyper-connected network with higher mobility of mobile genetic elements (MGEs), which facilitated horizontal gene transfer.Host identification analysis confirmed this mechanism, showing the S treatment effectively reduced potential ARG hosts to only two genera (PseudomonasandMoheibacter), significantly fewer than the 11 and 7 hosts identified in the control and R treatments, respectively. Partial least squares path modeling (PLS-PM) revealed that the sensitive strain uniquely reduced the influence of MGEs while enhancing temperature's role in ARG reduction. The findings establish that employing antibiotic-sensitive functional strains is a reliable strategy to mitigate environmental antibiotic resistance risks.