Porin biogenesis activates the σ~E response in Salmonella hfq mutants

摘要

In Salmonella enterica, loss of RNA chaperon Hfq promotes proteolytic cleavage of anti-σ~E factor RseA leading to the constitutive induction of the σ~E-dependent envelope stress response. Seeking to identify the source of the inducing signal, in the present study we measured RseA cleavage and σ~E-dependent transcription in strains lacking relevant outer membrane protein (omp) genes. We found removal of the main Salmonella porin, OmpD, to markedly reduce σ~E activation in hfq mutant cells. Subsequent removal of LamB and of OmpC further attenuated the response, indicating that different OMPs collectively contribute to the σ~E-activated phenotype. Thus, loss of Hfq-mediated regulation might cause unfolded OMPs to accumulate in the periplasm, triggering the σ~E response. These findings corroborate the role of Hfq protein as a pleio-tropic regulator of OMP biogenesis in Gram-negative bacteria.