title: Involvement of luxS in Biofilm Formation by Capnocytophaga ochracea.
abstract: Capnocytophaga ochracea is present in the dental plaque biofilm of patients with periodontitis. Biofilm cells change their phenotype through quorum sensing in response to fluctuations in cell-population density. Quorum sensing is mediated by auto-inducers (AIs). AI-2 is involved in intercellular signaling, and production of its distant precursor is catalyzed by LuxS, an enzyme involved in the activated methyl cycle. Our aim was to clarify the role of LuxS in biofilm formation by C. ochracea. Two luxS-deficient mutants, TmAI2 and LKT7, were constructed from C. ochracea ATCC 27872 by homologous recombination. The mutants produced significantly less AI-2 than the wild type. The growth rates of these mutants were similar to that of the wild-type in both undiluted Tryptic soy broth and 0.5 × Tryptic soy broth. However, according to crystal violet staining, they produced significantly less biofilm than the wild type. Confocal laser scanning microscopy and scanning electron microscopy showed that the biofilm of the TmAI2 strain had a rougher structure than that of the wild type. Complementation of TmAI-2 with extrinsic AI-2 from the culture supernatant of wild-type strain did not restore biofilm formation by the TmAI2 strain, but complementation of LKT7 strain with luxS partially restored biofilm formation. These results indicate that LuxS is involved in biofilm formation by C. ochracea, and that the attenuation of biofilm formation by the mutants is likely caused by a defect in the activated methyl cycle rather than by a loss of AI-2.
authors.affiliation: Department of Oral Medicine, Oral and Maxillofacial Surgery, Tokyo Dental College, 5-11-13 Sugano, Ichikawa, Chiba, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Hosohama-Saito
authors.affiliation: Department of Microbiology, Tokyo Dental College, 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo, Japan.
authors.forename: Eitoyo
authors.initials: E
authors.lastname: Kokubu
authors.affiliation: Department of Microbiology, Tokyo Dental College, 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo, Japan.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Okamoto-Shibayama
authors.affiliation: Department of Periodontology, Tokyo Dental College, 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo, Japan.
authors.forename: Daichi
authors.initials: D
authors.lastname: Kita
authors.affiliation: Department of Oral Medicine, Oral and Maxillofacial Surgery, Tokyo Dental College, 5-11-13 Sugano, Ichikawa, Chiba, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Katakura
authors.affiliation: Department of Microbiology, Tokyo Dental College, 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Ishihara
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D018441:Biofilms; D002206:Capnocytophaga / Q000235:genetics / Q000502:physiology*; D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000502:physiology*; D059765:Homologous Recombination; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D009154:Mutation
chemical_list: D001426:Bacterial Proteins; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria