LuxS affects biofilm maturation and detachment of the periodontopathogenic bacterium Eikenella corrodens

Previously, we reported that biofilm formation of Eikenella corrodens is regulated by autoinducer-2 (AI-2), based on observations that biofilm-forming efficiency of δluxS mutant was greater than that of the wild type (Azakami etal., J. Biosci. Bioeng., 102, 110-117, 2006). To determine whether the AI-2 molecule affects biofilm formation directly, we added purified AI-2 to luxS mutant and wild-type E.corrodens and compared biofilm formations by using a static assay. Results indicated that biofilm formation in E.corrodens was enhanced by the addition of AI-2. We also compared the biofilms formed by flow cell system for the luxS mutant and the wild type by using scanning electron microscopy and confocal laser scanning microscopy. The number of viable bacteria in the luxS mutant biofilm was dramatically reduced and more sparsely distributed than that of the wild type, which suggested that AI-2 might enhance the mature biofilm. Conversely, further analysis by modified confocal reflection microscopy indicated that the wild-type biofilm was matured earlier than that of the luxS mutant, and became thinner and more sparsely distributed with time. These data suggest that LuxS may facilitate the maturation and detachment of biofilm in E.corrodens.