Bacterial attachment and biofilm development
Initial work involved the isolation and characterization of bacteria found on the surfaces in a range of food processing environments. The attachment characteristics of three species of bacteria (S.liquefaciens, S.cohnii and P.fragi) isolated from the same production surface were examined. Mixed culture biofilm development was also modelled using these three organisms. The species were found to have differing attachment abilities and therefore cell surface characteristics such as outer membrane protein and lipopolysaccharide profiles, exopolysaccharide production, and cell surface hydrophobicity and charge were examined to explain these differences. All of these cell surface characteristics were subject to considerable variation in response to the environmental conditions. The outer membrane protein and lipopolysaccharide profiles did not show any relationship to attachment levels, and similarly exopolysaccharide production did not relate to the levels of attachment observed, although exopolysaccharide production was found to be particularly associated with attached cells. The attachment of S. cohnii and P jragi correlated to cell surface hydrophobicity, whilst the attachment of S.liquefaciens was dependent upon cell surface charge.