Role of Hyalin-like Protein in Gliding and Biofilm Formation by Capnocytophaga Ochracea.

Capnocytophaga ochracea possesses a type-IX secretion system that exports proteins which have a gliding motility-associated C-terminal (CTD) domain. This system is found in several species of the Bacteroidetes phylum. Hyalin, a large protein encoded by Coch_0033 in C. ochracea ATCC 27872, has a CTD domain and is posited to be involved in quorum sensing according to the database of the Kyoto Encyclopedia of Genes and Genomes. This suggests that it plays a role in biofilm formation via interbacterial communication. The aim of this study was to investigate the potential role of the hyalin-like protein coded by the Coch_0033 gene in gliding and biofilm formation of C. ochracea. A hyalin-like protein-deficient mutant strain of C. ochracea, designated mutant WR-1, was constructed through insertion of the ermF-ermAM cassette into the target gene. The spreading feature at the edge of the colony was lost in the mutant strain. Crystal violet and confocal laser scanning microscopy revealed no difference between the quantity of biofilm organized by the mutant and that organized by the wild-type strain. These data suggest that the hyalin-like protein encoded by the Coch_0033 gene is indeed involved in C. ochracea gliding activity.

Synergistic biofilm formation by Parvimonas micra and Fusobacterium nucleatum.

Parvimonas micra is frequently isolated from lesions of apical periodontitis and is a major disease-related pathogen. One of the main causes of apical periodontitis is extraradicular biofilm. In this study, we investigated polymicrobial biofilm formation by P. micra and species associated with apical periodontitis. The coaggregation activity of P. micra with partner strains was investigated by visual assays. Synergistic biofilm formation was evaluated by cocultures of P. micra and partner strains. Growth of planktonic cells was measured by evaluating the absorbance at OD660, and biofilm formation was examined by staining with crystal violet. The effects of soluble components on synergistic biofilm formation and planktonic cell growth were examined after coculture of P. micra and other strains separated with a 0.4-µm pore-size porous membrane. P. micra coaggregated with Fusobacterium nucleatum, Porphyromonas gingivalis, or Capnoctyophaga ochracea. P. micra showed no coaggregation with Staphylococcus aureus, S. epidermidis, or Prevotella intermedia. In mixed cultures, biofilm formation by P. micra and F. nucleatum was greater than that by P. micra and P. gingivalis or C. ochracea. In separated cocultures, planktonic cell growth of P. micra was enhanced by each of the three species. Biofilm formation by P. micra was enhanced by F. nucleatum or C. ochracea; however, no significant enhancement was observed with P. gingivalis. These data indicated that P. micra and F. nucleatum had synergistic effects in biofilm formation and that these effects may be important for colonization by these two species in apical periodontitis lesions.