title: Proteus mirabilis pmrI, an RppA-regulated gene necessary for polymyxin B resistance, biofilm formation, and urothelial cell invasion.
abstract: Proteus mirabilis is naturally resistant to polymyxin B (PB). To investigate the underlying mechanisms, Tn5 mutagenesis was performed, and a mutant exhibiting increased PB susceptibility was isolated. The mutant was found to have Tn5 inserted into the PpmrI (Proteus pmrI) gene, a gene which may encode a UDP-glucuronic acid decarboxylase. In other bacteria, pmrI belongs to the seven-gene pmrF operon, which is involved in lipopolysaccharide (LPS) modification. While the PpmrI knockout mutant had a wild-type LPS profile and produced amounts of LPS similar to those produced by the wild type, LPS of the knockout mutant had higher PB-binding activity than that of the wild type. PB could induce alterations of LPS in the wild type but not in the PpmrI knockout mutant. Moreover, the PpmrI knockout mutant exhibited decreased abilities in biofilm formation and urothelial cell invasion. Complementation of the PpmrI mutant with the full-length PpmrI gene led to restoration of the wild-type phenotypic traits. Previously we identified RppA, a response regulator of the bacterial two-component system, as a regulator of PB susceptibility and virulence factor expression in P. mirabilis. Here we showed that RppA could mediate the induction of PpmrI expression by PB. An electrophoretic mobility shift assay further demonstrated that RppA could bind directly to the putative PpmrI promoter. Together, these results provide a new insight into the regulatory mechanism underlying PB resistance and virulence expression in P. mirabilis.
authors.affiliation: Department and Graduate Institute of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan, Republic of China.
authors.forename: Sin-Sien
authors.initials: SS
authors.lastname: Jiang
authors.forename: Ming-Che
authors.initials: MC
authors.lastname: Liu
authors.forename: Lee-Jene
authors.initials: LJ
authors.lastname: Teng
authors.forename: Won-Bo
authors.initials: WB
authors.lastname: Wang
authors.forename: Po-Ren
authors.initials: PR
authors.lastname: Hsueh
authors.forename: Shwu-Jen
authors.initials: SJ
authors.lastname: Liaw
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D002262:Carboxy-Lyases / Q000235:genetics; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004847:Epithelial Cells / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006801:Humans; D008070:Lipopolysaccharides / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009876:Operon; D010641:Phenotype; D011112:Polymyxin B / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011513:Proteus mirabilis / Q000187:drug effects* / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D019459:Urothelium / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D008070:Lipopolysaccharides; D002262:Carboxy-Lyases; C023257:UDPglucuronate decarboxylase; D011112:Polymyxin B