title: The broadly conserved regulator PhoP links pathogen virulence and membrane potential in Escherichia coli.
abstract: PhoP is considered a virulence regulator despite being conserved in both pathogenic and non-pathogenic Enterobacteriaceae. While Escherichia coli strains represent non-pathogenic commensal isolates and numerous virulent pathotypes, the PhoP virulence regulator has only been studied in commensal E. coli. To better understand how conserved transcription factors contribute to virulence, we characterized PhoP in pathogenic E. coli. Deletion of phoP significantly attenuated E. coli during extraintestinal infection. This was not surprising since we demonstrated that PhoP differentially regulated the transcription of > 600 genes. In addition to survival at acidic pH and resistance to polymyxin, PhoP was required for repression of motility and oxygen-independent changes in the expression of primary dehydrogenase and terminal reductase respiratory chain components. All phenotypes have in common a reliance on an energized membrane. Thus, we hypothesized that PhoP mediates these effects by regulating genes encoding proteins that generate proton motive force. Indeed, bacteria lacking PhoP exhibited a hyperpolarized membrane and dissipation of the transmembrane electrochemical gradient increased susceptibility of the phoP mutant to acidic pH, while inhibiting respiratory generation of the proton gradient restored resistance to antimicrobial peptides independent of lipopolysaccharide modification. These findings demonstrate a connection between PhoP, virulence and the energized state of the membrane.
authors.affiliation: Department of Microbiology and Immunology, University of Michigan Medical School, 5641 West Medical Center Drive, Ann Arbor, MI 48109, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Alteri
authors.forename: Jonathon R
authors.initials: JR
authors.lastname: Lindner
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Reiss
authors.forename: Sara N
authors.initials: SN
authors.lastname: Smith
authors.forename: Harry L T
authors.initials: HL
authors.lastname: Mobley
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D006801:Humans; D007422:Intestines / Q000382:microbiology; D008564:Membrane Potentials; D051379:Mice; D008808:Mice, Inbred CBA; D014774:Virulence
chemical_list: D029968:Escherichia coli Proteins; C465562:PhoP protein, E coli