Potential roles of bacterial quorum sensing and biofilm formation in the biofouling process.

摘要

This thesis explored the potential roles of bacterial quorum sensing (QS) and biofilm formation in the biofouling process. Acyl homoserine lactone (AHLs) based bacterial QS in a natural subtidal biofilm was investigated for the first time. It was demonstrated that diverse AHLs molecules were present and variable in subtidal biofilms, with the dominant AHLs changed from short- to long-chain over time. Most cultivable AHLs-producing bacteria in subtidal biofilms belonged to Pseudoalteromonas spp., Vibrio spp. and Rhodobacteraceae family. The AHLs-active marine bacteria in the phylum Bacteroidetes and in the genera Silicibacter, Ruegeria, and Thalassomonas were report here for the first time. TRFLP analysis revealed that the AHLs-producing bacteria were dynamic in the biofilm community and Vibrio spp. was one of the pioneer groups in surface colonization. Potential roles of AHLs in macro-fouling were then investigated. Individual AHLs in seawater solution affected larval behavior in Hydroides elegans, while mixed AHLs in agarose gel enhanced larval settlement of H. elegans and Balanus amphitrite, suggesting that AHLs may serve as chemical indicators for settling larvae.; In addition, the possible relevance of biofilm formation of the marine bacterium Pseudoalteromonas spongiae for its inductiveness to larval settlement of the polychaete H. elegans was investigated. It was proposed that culture conditions and chloramphenicol treatments affected bacterial biofilm formation, which in turn affected larval settlement of H. elegans.; Overall, my research pointed out the potential involvement of bacterial quorum sensing and biofilm formation in the biofouling process, which extended our understanding of the interactions between bacteria and bacteria, and bacterial biofilms and settling invertebrate larvae during the biofouling process.