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Effect of environmental conditions on bacterial community structure and chemical profile of multispecies biofilms in relation to larval settlement of benthic invertebrates

Authors Chung, Hong Chun
Issue Date 2010
Summary Earlier studies have shown that biofilms can mediate larval settlement of many benthic invertebrates including the polychaete Hydroides elegans and the barnacle Balanus amphitrite; changes in bacterial community structure and other biofilm attributes influence the larval settlement response. However, the chemical cues mediating the settlement response remain unknown. Molecular tools: Phylochip, denaturing gradient gel electrophoresis (DGGE), pyrosequencing and clone library construct, and chemical analytic tools: gas chromatography-mass spectrometry (GC-MS) and ultra performance liquid chromatography-mass spectrometry (UPLC-MS) were used to provide in-depth analysis on bacterial community structure and chemical profile of biofilms at different environmental conditions. Age showed a greater effect on shaping the bacterial community structure but less effect on chemical profile than substratum did. However, biofilm extracts induced larval settlement of H. elegans in a biofilm-age-dependent manner, suggesting that specific settlement cues are involved and the larval settlement response cannot be predicted by the overall chemical composition of the biofilm alone. Pyrosequencing revealed extremely high biodiversity in biofilms ever reported and a high portion of rare population. Bacterial community comparison between intertidal and subtidal biofilims indicated that Cyanobacteria were more abundant in intertidal biofilms whereas Proteobacteria were more abundant in subtidal biofilms. Moreover, I demonstrated that larval settlement of B. amphitrite is a chemically-mediated process by chemical choice assay. Principal components analysis (PCA) and preliminary compound matching indicated that the major difference in chemical profile between intertidal and subtidal biofilms is the presence of some amino acid derivatives and this may explain the preferential settlement of barnacle in the intertidal zone.
Note Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2010
Language English
Format Thesis
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