RNA chaperone that binds small regulatory RNA (sRNAs) and mRNAs to facilitate mRNA translational regulation in response to envelope stress, environmental stress and changes in metabolite concentrations. Also binds with high specificity to tRNAs (By similarity). Essential for virulence in the suckling mouse model of cholera pathogenesis. A hfq deletion mutant cannot colonize the murine small intestine despite retaining the ability to produce the colonization factor TCP. Deletion of hfq does not impair production of the sigma factor RpoS. Expression and activity of the sigma factor sigma-E are dramatically increased in the hfq mutant. Belongs to the Hfq family.