Studies on bioflim formation and survival mechanisms of Campylobacter species in foods

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We observed that Campylobacter jejuni strain 81-176, a strong slime producer, showed spreading and highly mucoid colonies on blood agar plates, and formed biofilm on the bottom of a glass flask after stationary cultivation in Brucella broth. The present study was performed to examine the mode of C. jejuni adherence to a smooth surface. When bacterial suspensions in Brucella broth were incubated in a microplate well, microcolonies were formed on the coverslip by 2 h after incubation. The microcolonies gradually grew and formed a biofilm of net-like connections by 6 h. Transmission electron microscopy indicated that massive amounts of extracellular material were masking the cell surface and bound ruthenium red, suggesting the presence of a poiysaccharide moiety. Scanning electron microscopy indicated that the flagella acted as bridges, forming a net-like connection between the organisms. To determine the genes associated with biofilm formation, several mutants were constructed from strain 81-176 by natural transformation-madiated allelic exchange. As aflagellate (flaAB and flbA) and flagellate but nonmotile (pflA and motA) mutants did not form a biofilm exhibited by the wild type strain even though capsular-like polysaccharide was expressed on the cell surface. In contrast, kpsM and peb1 mutants which lack capsular-like polysaccharide and a outer membrane protein, respectively, retained the ability of biofilm formation. These findings suggest that flagella-mediated motility but not capsular-like polysaccharide and PEB 1 protein is needed for biofilm formation in vitro.