title: Membrane topology of Salmonella invasion protein SipB confers osmotolerance.
abstract: Salmonella enterica serovar Typhimurium is a major cause of human gastrointestinal illness worldwide. This pathogen can persist in a wide range of environments, making it of great concern to public health. Here, we report that the salmonella pathogenicity island (SPI)-1 effector protein SipB exhibits a membrane topology that confers bacterial osmotolerance. Disruption of the sipB gene or the invG gene (SPI-1 component) significantly reduced the osmotolerance of S. Typhimurium LT2. Biochemical assays showed that NaCl osmolarity increased the membrane topology of SipB, and a neutralising antibody against SipB reduced osmotolerance in the WT strain. The WT strain, but not the sipB mutant, exhibited elevated cyclopropane fatty acid C19:0 during conditions of osmotic stress, correlating with the observed levels of survival and membrane integrity. This result suggests a link between SipB and the altered fatty acid composition induced upon exposure to osmotic stress. Overall, our findings provide the first evidence that the Salmonella virulence translocon SipB affects membrane fluidity and alters bacterial osmotolerance.
authors.affiliation: Division of Biomedical Food Research, National Institute of Health Sciences, Kamiyoga 1-18-1, Setagaya-ku, Tokyo 158-8501, Japan. hasakura@nihs.go.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Asakura
authors.forename: Tomoya
authors.initials: T
authors.lastname: Ekawa
authors.forename: Naoki
authors.initials: N
authors.lastname: Sugimoto
authors.forename: Yoshika
authors.initials: Y
authors.lastname: Momose
authors.forename: Keiko
authors.initials: K
authors.lastname: Kawamoto
authors.forename: Sou-Ichi
authors.initials: S
authors.lastname: Makino
authors.forename: Shizunobu
authors.initials: S
authors.lastname: Igimi
authors.forename: Shigeki
authors.initials: S
authors.lastname: Yamamoto
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D002462:Cell Membrane / Q000737:chemistry*; D005227:Fatty Acids / Q000032:analysis; D044404:Genomic Islands / Q000235:genetics; D006801:Humans; D008560:Membrane Fluidity; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D009995:Osmosis; D009997:Osmotic Pressure; D012480:Salmonella Infections / Q000382:microbiology*; D012486:Salmonella typhimurium / Q000472:pathogenicity*; D012965:Sodium Chloride / Q000737:chemistry; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D005227:Fatty Acids; D008565:Membrane Proteins; C094579:invasion protein B, Salmonella typhimurium; D012965:Sodium Chloride