title: LitR is a repressor of syp genes and has a temperature-sensitive regulatory effect on biofilm formation and colony morphology in Vibrio (Aliivibrio) salmonicida.
abstract: Vibrio (Aliivibrio) salmonicida is the etiological agent of cold water vibriosis, a disease in farmed Atlantic salmon (Salmo salar) that is kept under control due to an effective vaccine. A seawater temperature below 12°C is normally required for disease development. Quorum sensing (QS) is a cell density-regulated communication system that bacteria use to coordinate activities involved in colonization and pathogenesis, and we have previously shown that inactivation of the QS master regulator LitR attenuates the V. salmonicida strain LFI1238 in a fish model. We show here that strain LFI1238 and a panel of naturally occurring V. salmonicida strains are poor biofilm producers. Inactivation of litR in the LFI1238 strain enhances medium- and temperature-dependent adhesion, rugose colony morphology, and biofilm formation. Chemical treatment and electron microscopy of the biofilm identified an extracellular matrix consisting mainly of a fibrous network, proteins, and polysaccharides. Further, by microarray analysis of planktonic and biofilm cells, we identified a number of genes regulated by LitR and, among these, were homologues of the Vibrio fischeri symbiosis polysaccharide (syp) genes. The syp genes were regulated by LitR in both planktonic and biofilm lifestyle analyses. Disruption of syp genes in the V. salmonicida ΔlitR mutant alleviated adhesion, rugose colony morphology, and biofilm formation. Hence, LitR is a repressor of syp transcription that is necessary for expression of the phenotypes examined. The regulatory effect of LitR on colony morphology and biofilm formation is temperature sensitive and weak or absent at temperatures above the bacterium's upper threshold for pathogenicity.
authors: The Molecular Biosystems Research Group, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway Norwegian Structural Biology Centre, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway hilde.hansen@uit.no.
authors: Hilde
authors: H
authors: Hansen
authors: Section for Microbiology, Immunology and Parasitology, Department of Food Safety and Infection Biology, Faculty of Veterinary Medicine and Biosciences, Norwegian University of Life Sciences, Ås, Norway.
authors: Ane Mohn
authors: AM
authors: Bjelland
authors: The Molecular Biosystems Research Group, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway.
authors: Maria
authors: M
authors: Ronessen
authors: The Molecular Biosystems Research Group, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway Norwegian Structural Biology Centre, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway.
authors: Espen
authors: E
authors: Robertsen
authors: The Molecular Biosystems Research Group, Department of Chemistry, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway Norwegian Structural Biology Centre, Faculty of Science and Technology, UiT-The Arctic University of Norway, Tromsø, Norway.
authors: Nils Peder
authors: NP
authors: Willassen
mesh_terms: D059707:Aliivibrio Infections / Q000382:microbiology / Q000662:veterinary; D044165:Aliivibrio salmonicida / Q000235:genetics / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D000818:Animals; D018441:Biofilms / Q000254:growth & development* / Q000528:radiation effects; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005393:Fish Diseases / Q000382:microbiology; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006483:Hemorrhagic Septicemia / Q000382:microbiology / Q000662:veterinary; D008969:Molecular Sequence Data; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D020317:Salmo salar; D017422:Sequence Analysis, DNA; D013696:Temperature
chemical_list: D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; D012097:Repressor Proteins