Biocomplexity of the interactions of complex organic colloids and microbial communities in aquatic environments

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Dissolved and colloidal organic matter (DOM and COM) represents the largest reservoir of organic carbon in the oceans and play a substantial role in global cycling of carbon. In the present project, we were aimed at examining degradation of complex organic polymers in seawater and regulation mechanisms of bacterial communities in estuarine and coastal environments. We succeeded in developing a novel tracer technique to analyze transformation and degradation of complex organic polymers in seawater. Results showed that peptidoglycan, an important component of marine COM, is degraded more slowly than proteins, suggesting that complex polymers play a role in preservation of organic matter. Single-cell detection methods were used to investigate community dynamics and regulation of bacterial communities, which are responsible for degradation of DOM and COM. We found that bacterial community composition varies depending on substrate (DOM) supply, but the major flux of DOM and COM is generally driven by a limited number of bacterial groups such as alpha proteobacteria cluster. These results have implications for better modeling the biocomplex system consisting of DOC, COC and microbial communities.