Lithium enhanced plasmid-mediated conjugative transfer of antimicrobial resistance genes in Escherichia coli: Different concentrations and mechanisms

Abstract

Conjugative transfer, a pivotal mechanism in the transmission of antimicrobial resistance genes, is susceptible to various environmental pollutants. As an emerging contaminant, lithium (Li) has garnered much attention due to its extensive applications. This research investigated the effects of Li on conjugative transfer process, examining biochemical and omics perspectives. Results revealed that Li could increase the conjugative transfer frequency of both donor and recipient via different mechanisms at varying concentrations. At 0.1 mg/L LiCl, a notable increase in conjugative transfer frequency occurred without ROS elevation. However, the surge of ROS was identified as a crucial regulator at 100 mg/L LiCl, as eliminating ROS would significantly decrease the conjugative transfer frequency. Besides, comparative transcriptome analysis revealed consistent variations in “SOS response”, “quorum sensing” and “oxidative phosphorylation” pathways at both 0.1 mg/L and 100 mg/L LiCl concentrations, suggesting their pivotal roles as targets for Li regulation and is independent of Li concentration. While genes related to “conjugative transfer”, “pili”, “outer membrane protein” and “antioxidant enzyme” were only significantly regulated by 100 mg/L LiCl, possible to be the specific reasons for High (100 mg/L) LiCl increased conjugative transfer frequency. This study reveals the distinct effects and mechanisms of different concentration of Li on conjugative transfer in E. coli, providing a theoretical basis for the understanding of the environmental effects of Li.