title: Deletion of mtrC in Haemophilus ducreyi increases sensitivity to human antimicrobial peptides and activates the CpxRA regulon.
abstract: Haemophilus ducreyi resists killing by antimicrobial peptides encountered during human infection, including cathelicidin LL-37, α-defensins, and β-defensins. In this study, we examined the role of the proton motive force-dependent multiple transferable resistance (MTR) transporter in antimicrobial peptide resistance in H. ducreyi. We found a proton motive force-dependent effect on H. ducreyi's resistance to LL-37 and β-defensin HBD-3, but not α-defensin HNP-2. Deletion of the membrane fusion protein MtrC rendered H. ducreyi more sensitive to LL-37 and human β-defensins but had relatively little effect on α-defensin resistance. The mtrC mutant 35000HPmtrC exhibited phenotypic changes in outer membrane protein profiles, colony morphology, and serum sensitivity, which were restored to wild type by trans-complementation with mtrC. Similar phenotypes were reported in a cpxA mutant; activation of the two-component CpxRA regulator was confirmed by showing transcriptional effects on CpxRA-regulated genes in 35000HPmtrC. A cpxR mutant had wild-type levels of antimicrobial peptide resistance; a cpxA mutation had little effect on defensin resistance but led to increased sensitivity to LL-37. 35000HPmtrC was more sensitive than the cpxA mutant to LL-37, indicating that MTR contributed to LL-37 resistance independent of the CpxRA regulon. The CpxRA regulon did not affect proton motive force-dependent antimicrobial peptide resistance; however, 35000HPmtrC had lost proton motive force-dependent peptide resistance, suggesting that the MTR transporter promotes proton motive force-dependent resistance to LL-37 and human β-defensins. This is the first report of a β-defensin resistance mechanism in H. ducreyi and shows that LL-37 resistance in H. ducreyi is multifactorial.
authors: Department of Microbiology and Immunology, Indiana University School of Medicine, 635 Barnhill Drive, Room MS 420, Indianapolis, Indiana 46202-5124, USA.
authors: Sherri D
authors: SD
authors: Rinker
authors: Michael P
authors: MP
authors: Trombley
authors: Xiaoping
authors: X
authors: Gu
authors: Kate R
authors: KR
authors: Fortney
authors: Margaret E
authors: ME
authors: Bauer
mesh_terms: D023181:Antimicrobial Cationic Peptides / Q000276:immunology / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000276:immunology* / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D001483:Base Sequence; D002602:Chancroid / Q000276:immunology / Q000382:microbiology*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D005798:Genes, Bacterial / Q000235:genetics; D006191:Haemophilus ducreyi / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity* / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology; D018085:Regulon / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017421:Sequence Analysis; D023084:alpha-Defensins / Q000276:immunology / Q000378:metabolism; D023083:beta-Defensins / Q000276:immunology / Q000378:metabolism; D054804:Cathelicidins
chemical_list: D023181:Antimicrobial Cationic Peptides; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D023084:alpha-Defensins; D023083:beta-Defensins; C085504:CpxR protein, Bacteria; D011494:Protein Kinases; C092472:CpxA protein, bacteria; D054804:Cathelicidins