Abstract
Bacterial sensing of environmental signals through the two-component system (TCS) plays a key role in modulating virulence. In the search for the host hormone-sensing TCS, we identified a conserved qseEGF locus following glmY, a small RNA (sRNA) gene in uropathogenic Proteus mirabilis. Genes of glmY-qseE-qseG-qseF constitute an operon, and QseF binding sites were found in the glmY promoter region. Deletion of glmY or qseF resulted in reduced swarming motility and swarming-related phenotypes relative to the wild-type and the respective complemented strains. The qseF mutant had decreased glmYqseEGF promoter activity. Both glmY and qseF mutants exhibited decreased flhDC promoter activity and mRNA level, while increased rcsB mRNA level was observed in both mutants. Prediction by TargetRNA2 revealed cheA as the target of GlmY. Then, construction of the translational fusions containing various lengths of cheA 5'UTR for reporter assay and site-directed mutagenesis were performed to investigate the cheA-GlmY interaction in cheA activation. Notably, loss of glmY reduced the cheA mRNA level, and urea could inhibit swarming in a QseF-dependent manner. Altogether, this is the first report elucidating the underlying mechanisms for modulation of swarming motility by a QseEF-regulated sRNA GlmY, involving expression of cheA, rcsB and flhDC in uropathogenic P. mirabilis.