Quorum sensing luxI/R genes enhances cadmium detoxification in Aeromonas by up-regulating EPS production and cadmium resistance genes

Abstract

The increasing cadmium (Cd) contamination in the environment poses a serious threat to ecosystem health and human safety. This study investigated the roles of quorum sensing (QS) genes luxI/R, key components of the QS system, in the Cd accumulation and detoxification in Aeromonas. Pan-genome analysis showed that luxI/R and Cd resistance genes were highly conserved in Aeromonas species. Strains of luxI/R knockout, complementation and overexpression were constructed via homologous recombination. The luxI/R deletion significantly reduced Cd removal by up to 32%, decreased extracellular protein (18-36%) and polysaccharide (19-33%) contents, whereas luxI/R overexpression enhanced Cd removal capacity by 11%. Transcriptomic and metabolomic analyses further revealed coordinated changes. In the ΔluxI/R strain, genes involved in assimilatory sulfate reduction and arginine biosynthesis were downregulated, accompanied by reduced levels of glycerophospholipid, vitamin, and cytochrome P450-related metabolites. In contrast, luxI/R overexpression upregulated arginine synthesis (2.0~3.5-fold) and sulfate assimilation (1.4~2.4-fold) genes, with corresponding increases of metabolites. Together these findings demonstrate that luxI/R genes may play a crucial role in regulation of EPS production and Cd resistance gene expression, thus enhancing our understanding of microbial Cd detoxification mechanisms.