Broad adaptations of plasmid-carrying Escherichia coli and Klebsiella pneumoniae to water as a reservoir

Abstract The spread of antimicrobial-resistant Enterobacterales is a major One Health issue, with aquatic environments increasingly recognized as potential reservoirs. However, data on bacterial adaptation to water is limited. We examined the survival and transcriptomic adaptation of Escherichia coli and Klebsiella pneumoniae , including plasmid-cured variants (PCVs), during 14 days in sterilized tap and river water. The strains belonged to sequence types (ST)648 and ST307, representing international high-risk clonal lineages. Viable cell counts of wild-type strains and PCVs remained stable in both water types. We used RNA sequencing, followed by functional analysis of the differentially expressed genes. Considerable transcriptomic changes occurred, especially in K. pneumoniae , with extensive regulation of genes related to inorganic ion transport, and coenzyme and nutrient transport and metabolism. Adaptational differences between wild-type strains and PCVs highlighted plasmid-associated effects. These findings demonstrate strain-specific adaptive responses to aquatic environments and underline the context-dependent influence of plasmids in shaping adaptation.