Project description: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.
Project description:Brain abscesses are occasionally associated with a dental source of infection. An unusual case of frontal lobe abscess in a nonimmunocompromised child infected with multidrug-resistant Capnocytophaga ochracea is described and confirms the pathogenic potential of this organism to cause human disease in the central nervous system.
Project description:Capnocytophaga ochracea (Prévot et al. 1956) Leadbetter et al. 1982 is the type species of the genus Capnocytophaga. It is of interest because of its location in the Flavobacteriaceae, a genomically not yet charted family within the order Flavobacteriales. The species grows as fusiform to rod shaped cells which tend to form clumps and are able to move by gliding. C. ochracea is known as a capnophilic (CO(2)-requiring) organism with the ability to grow under anaerobic as well as aerobic conditions (oxygen concentration larger than 15%), here only in the presence of 5% CO(2). Strain VPI 2845(T), the type strain of the species, is portrayed in this report as a gliding, Gram-negative bacterium, originally isolated from a human oral cavity. Here we describe the features of this organism, together with the complete genome sequence, and annotation. This is the first completed genome sequence from the flavobacterial genus Capnocytophaga, and the 2,612,925 bp long single replicon genome with its 2193 protein-coding and 59 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.
Project description:A beta-lactamase gene (cfxA3, 966 bp) was isolated from a beta-lactam-resistant Capnocytophaga ochracea clinical isolate and amplified using primers from the cfxA gene of Bacteroides vulgatus. The MICs of third-generation cephalosporins were much higher than those of the transconjugant Escherichia coli strain. The deduced protein sequence, by comparison with CfxA2 of Prevotella intermedia, had a Y239D substitution and possessed the characteristics of a class A, group 2e beta-lactamase.
Project description:Capnocytophaga ochracea is a Gram-negative, rod-shaped bacterium that demonstrates gliding motility when cultured on solid agar surfaces. C. ochracea possesses the ability to form biofilms; however, factors involved in biofilm formation by this bacterium are unclear. A type IX secretion system (T9SS) in Flavobacterium johnsoniae was shown to be involved in the transport of proteins (e.g., several adhesins) to the cell surface. Genes orthologous to those encoding T9SS proteins in F. johnsoniae have been identified in the genome of C. ochracea; therefore, the T9SS may be involved in biofilm formation by C. ochracea. Here we constructed three ortholog-deficient C. ochracea mutants lacking sprB (which encodes a gliding motility adhesin) or gldK or sprT (which encode T9SS proteins in F. johnsoniae). Gliding motility was lost in each mutant, suggesting that, in C. ochracea, the proteins encoded by sprB, gldK, and sprT are necessary for gliding motility, and SprB is transported to the cell surface by the T9SS. For the ?gldK, ?sprT, and ?sprB strains, the amounts of crystal violet-associated biofilm, relative to wild-type values, were 49%, 34%, and 65%, respectively, at 48 h. Confocal laser scanning and scanning electron microscopy revealed that the biofilms formed by wild-type C. ochracea were denser and bacterial cells were closer together than in those formed by the mutant strains. Together, these results indicate that proteins exported by the T9SS are key elements of the gliding motility and biofilm formation of C. ochracea.
Project description:Bacterial outer membrane vesicles (OMVs) are spherical lipid bilayer nanostructures released by bacteria that facilitate oral biofilm formation via cellular aggregation and intercellular communication. Recent studies have revealed that Capnocytophaga ochracea is one of the dominant members of oral biofilms; however, their potential for OMV production has yet to be investigated. This study demonstrated the biogenesis of OMVs in C. ochracea associated with the concentration of unsaturated fatty acids of phosphatidylinositol (PI) and characterized the size and protein profile of OMVs produced at growth phases. Transmission electron microscopy showed isolated spherical structures from cells stained with heavy metals, indicating the production of OMVs with a size ranging from 25 to 100 nm. Lipidome analysis revealed the presence of phosphatidic acid, phosphatidylethanolamine, phosphatidylcholine, and PI as the main lipids. Some unsaturated fatty acids of PI were present specifically in OMV and little in the outer membrane, suggesting that OMVs are generated from a specific region of the membrane through blebbing rather than a random process such as cell lysis. Furthermore, the lack of similar PI accumulation in the OMV of Porphyromonas gingivalis suggests that C. ochracea has a different biogenesis mechanism. The blebbing mechanism was further supported by higher OMV production occurring at the exponential phase in comparison to the stationary phase, where cell lysis is more likely to occur. Further, comparative protein profile of OMVs isolated under different growth phases may indicate that the OMV cargo does not largely vary with growth phases. The present study provides a basis for further understanding the roles of C. ochracea OMVs in oral biofilms as well as systemic diseases that C. ochracea involves.