RpoS Acts as a Global Repressor of Virulence Gene Expression in Escherichia coli O104:H4 and Enteroaggregative E coli.

This article focuses on the role of the alternative sigma factor RpoS in regulating virulence gene expression in Escherichia coli O104:H4, the pathogen responsible for the 2011 enterohemorrhagic E coli (EHEC) outbreak in Germany. The study identifies a single-nucleotide polymorphism (SNP) in the rpoS start codon (ATG > ATA) that reduces RpoS levels and leads to enhanced expression of enteroaggregative E coli (EAEC)-specific virulence factors, primarily through derepression of aggR, the master regulator of EAEC virulence. Deletion of rpoS in E coli O104:H4 and typical EAEC strains similarly increased virulence-related phenotypes such as bacterial aggregation, biofilm formation, epithelial adherence, and inflammatory response. These findings demonstrate that RpoS functions as a global repressor of virulence in E coli O104:H4 by modulating AggR-dependent gene expression, highlighting its importance in the pathogen’s adaptation and pathogenicity.