Application of the Microbial Population Analysis Methods for the Investigation of Sediment Transfer and Materials Conversion Functions

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The applicability of microbial population to investigate the sediment transfer phenomena was investigated. Samples were obtained mainly from Ariake Bay. In 2005 and 2006, samples were obtained from 23 points in Ariake Bay, and horizontal distribution of beta proteobacterial ammonia oxidizing bacteria was studied by the T-RFLP method. It was found that some of the OTUs (operational taxonomic units) distributed along the counter-clockwise flow of influent from Chikugo-River, and others were found more in the central part of the Ariake-Bay. It has been reported by other researchers that the influent from Chikugo-River has a counterclockwise flow, and the present study gave the same outcome. In 2007, an intensive sampling was done on 29th September at 5 locations with a multiple-time-point sampling. The whole bacterial community in the sediment samples and the bottom water samples were analyzed by the T-RFLP method. Prior to the study, a new DNA extraction method using sonication was developed, to enhance the throughput of the analysis with minimum amount of sample. By the developed method, PCR products were obtained from most of the samples only by sonication and dilution. In the same way, PCR products were obtained from suspended solids in the samples. PCR-T-RFLP method was applied to investigate the behavior of microorganisms in the bottom water within the short period of time on the sampling day. The dynamic behavior of the microbial population in the bottom water and its suspended solids samples were observed by the developed method. But unfortunately, in the present study, clear relationship between the sediment transfer and the microbial population change could not be found. It may be necessary to find key bacterial species that are suitable as a tracer. In conclusion, we developed a method to use microbial population structure to monitor the behavior of sediment and its transfer.