title: Flagella-independent surface motility in Salmonella enterica serovar Typhimurium.
abstract: Flagella are multiprotein complexes necessary for swimming and swarming motility. In Salmonella enterica serovar Typhimurium, flagella-mediated motility is repressed by the PhoP/PhoQ regulatory system. We now report that Salmonella can move on 0.3% agarose media in a flagella-independent manner when experiencing the PhoP/PhoQ-inducing signal low Mg(2+). This motility requires the PhoP-activated mgtA, mgtC, and pagM genes, which specify a Mg(2+) transporter, an inhibitor of Salmonella's own F1Fo ATPase, and a small protein of unknown function, respectively. The MgtA and MgtC proteins are necessary for pagM expression because pagM mRNA levels were lower in mgtA and mgtC mutants than in wild-type Salmonella, and also because pagM expression from a heterologous promoter rescued motility in mgtA and mgtC mutants. PagM promotes group motility by a surface protein(s), as a pagM-expressing strain conferred motility upon a pagM null mutant, and proteinase K treatment eliminated motility. The pagM gene is rarely found outside subspecies I of S. enterica and often present in nonfunctional allelic forms in organisms lacking the identified motility. Deletion of the pagM gene reduced bacterial replication on 0.3% agarose low Mg(2+) media but not in low Mg(2+) liquid media. Our findings define a form of motility that allows Salmonella to scavenge nutrients and to escape toxic compounds in low Mg(2+) semisolid environments.
authors.affiliation: Howard Hughes Medical Institute and Department of Microbial Pathogenesis, Yale School of Medicine, Boyer Center for Molecular Medicine, New Haven, CT 06536-0812; and Yale Microbial Sciences Institute, West Haven, CT 06516.
authors.forename: Sun-Yang
authors.initials: SY
authors.lastname: Park
authors.affiliation: Howard Hughes Medical Institute and Department of Microbial Pathogenesis, Yale School of Medicine, Boyer Center for Molecular Medicine, New Haven, CT 06536-0812; and Yale Microbial Sciences Institute, West Haven, CT 06516.
authors.forename: Mauricio H
authors.initials: MH
authors.lastname: Pontes
authors.affiliation: Howard Hughes Medical Institute and Department of Microbial Pathogenesis, Yale School of Medicine, Boyer Center for Molecular Medicine, New Haven, CT 06536-0812; and Yale Microbial Sciences Institute, West Haven, CT 06516 eduardo.groisman@yale.edu.
authors.forename: Eduardo A
authors.initials: EA
authors.lastname: Groisman
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D027682:Cation Transport Proteins / Q000378:metabolism*; D019295:Computational Biology; D005407:Flagella / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D008274:Magnesium / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D025261:Mitochondrial Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D008969:Molecular Sequence Data; D009068:Movement / Q000502:physiology*; D016296:Mutagenesis; D012486:Salmonella typhimurium / Q000502:physiology*; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D027682:Cation Transport Proteins; D026901:Membrane Transport Proteins; C079792:PhoQ protein, Bacteria; C061064:PhoP protein, Bacteria; D000251:Adenosine Triphosphatases; C474451:F1F0-ATP synthase; C093585:MgtA protein, bacteria; C093586:MgtC protein, Salmonella typhimurium; D025261:Mitochondrial Proton-Translocating ATPases; D008274:Magnesium
keywords: MgtA; MgtC; PagM; PhoP/PhoQ; magnesium