Overlooked closed reactor thermal steam discharge: steering ARGs fate and microbiome evolution in kitchen...

Steam condensation and reflux in closed conditions impairs composting efficiency, which can be effectively addressed by a negative pressure condensation system. However, microecological dynamics driving microbial succession and antibiotic resistance genes (ARGs) fate during steam discharge-induced rapid maturation remain unclear. This study investigates the effect of real-time steam emission on the removal of ARGs in a closed composting system. Results show that steam discharge significantly expedites the temperature elevation and boosts the high-temperature removal efficiency of ARGs. Compared with the initial level, the total abundance removal rate of target ARGs reached 98 %. However, it promotes the spread and enrichment of specific ARGs (tetX, aadA, strB, ermF, and sul2) during the maturity stage by stimulating bacterial community dynamics, thereby reducing the removal rate to 68 %. The main mechanisms affecting ARGs changes are as follows: steam discharge relieves the environmental stress on bacteria, shifts community assembly toward non-dominant stochastic processes (|βNTI| < 2), thereby enhancing biodiversity (Shannon index) and the stability of bacterial communities. Meanwhile, these highly active bacteria exhibit strong network connectivity, facilitating horizontal gene transfer (HGT) mediated by intl1 and intl2 during the maturation stage. This study shows steam emission improves ARGs removal but exacerbates specific ARGs spread via microbial redistribution.