title: The cabABC Operon Essential for Biofilm and Rugose Colony Development in Vibrio vulnificus.
abstract: A transcriptome analysis identified Vibrio vulnificus cabABC genes which were preferentially expressed in biofilms. The cabABC genes were transcribed as a single operon. The cabA gene was induced by elevated 3',5'-cyclic diguanylic acid (c-di-GMP) and encoded a calcium-binding protein CabA. Comparison of the biofilms produced by the cabA mutant and its parent strain JN111 in microtiter plates using crystal-violet staining demonstrated that CabA contributed to biofilm formation in a calcium-dependent manner under elevated c-di-GMP conditions. Genetic and biochemical analyses revealed that CabA was secreted to the cell exterior through functional CabB and CabC, distributed throughout the biofilm matrix, and produced as the biofilm matured. These results, together with the observation that CabA also contributes to the development of rugose colony morphology, indicated that CabA is a matrix-associated protein required for maturation, rather than adhesion involved in the initial attachment, of biofilms. Microscopic comparison of the structure of biofilms produced by JN111 and the cabA mutant demonstrated that CabA is an extracellular matrix component essential for the development of the mature biofilm structures in flow cells and on oyster shells. Exogenously providing purified CabA restored the biofilm- and rugose colony-forming abilities of the cabA mutant when calcium was available. Circular dichroism and size exclusion analyses revealed that calcium binding induces CabA conformational changes which may lead to multimerization. Extracellular complementation experiments revealed that CabA can assemble a functional matrix only when exopolysaccharides coexist. Consequently, the combined results suggested that CabA is a structural protein of the extracellular matrix and multimerizes to a conformation functional in building robust biofilms, which may render V. vulnificus to survive in hostile environments and reach a concentrated infective dose.
authors.affiliation: National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul, South Korea.
authors.forename: Jin Hwan
authors.initials: JH
authors.lastname: Park
authors.affiliation: National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul, South Korea.
authors.forename: Youmi
authors.initials: Y
authors.lastname: Jo
authors.affiliation: Infection and Immunity Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.
authors.forename: Song Yee
authors.initials: SY
authors.lastname: Jang
authors.affiliation: National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul, South Korea; Infection and Immunity Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.
authors.forename: Haenaem
authors.initials: H
authors.lastname: Kwon
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington, United States of America.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Irie
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington, United States of America.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Parsek
authors.affiliation: Infection and Immunity Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.
authors.forename: Myung Hee
authors.initials: MH
authors.lastname: Kim
authors.affiliation: National Research Laboratory of Molecular Microbiology and Toxicology, Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul, South Korea.
authors.forename: Sang Ho
authors.initials: SH
authors.lastname: Choi
mesh_terms: D000595:Amino Acid Sequence; D018441:Biofilms; D002135:Calcium-Binding Proteins / Q000378:metabolism; D005798:Genes, Bacterial; D006801:Humans; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D009876:Operon; D011135:Polysaccharides, Bacterial / Q000235:genetics* / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D041261:Vibrio vulnificus / Q000502:physiology*
chemical_list: D002135:Calcium-Binding Proteins; D011135:Polysaccharides, Bacterial