Analysis on functions of micro-animals in the detritus food webs of biological wastewater treatment systems.

本研究旨在阐明污水生物处理系统中微生物生态系统与污水净化功能之间的关系。从日本典型的生活污水生物处理设施Johkasou系统中分离到部分细菌，并对分离到的细菌进行16SrRNA序列鉴定。适当的细菌(粘质沙雷氏菌等)为研究废水处理过程中微生物生态系统的功能。此外，T-RFLP方法是分析废水处理系统中复杂微生物生态系统的一种有用的分子生物学工具。并对一些柔克索细菌进行分离。结果表明，该菌为褐飞虱(Philodina sp.利用Philodina sp.的过滤作用和混凝作用制得高透明度的水是非常有效的。此外，我们还得到了在捕食细菌的条件下，Philodina sp.对有机碳的矿化比在细菌单一培养条件下的矿化更快的结果。嗜热纤毛虫的存在提高了DOC和TOC的总降幅。在混合培养体系中，以细菌为缩影系统，以简单的碎屑食物网状结构。另一方面，对一个简单的捕食者-食饵模型进行了数值分析，得出了与我们的实验结果相矛盾的结果。也就是说，我们的实验结果有力地表明，原生动物和后生动物等捕食者的存在增加了细菌分解有机物的活性，因为细菌和原生动物之间简单的捕食相互作用只会导致作为有机物分解者的细菌数量减少。

In this study, it aimed to clarify the relations between the microbial ecosystems in biological wastewater treatment systems and its purification functions for waste water. Some bacteria were isolated from Johkasou systems, which are typical on-site biological domestic wastewater treatment facilities in Japan, and the isolated bacteria were identified by sequences of 16SrRNA. Some appropriate bacteria (Serratia marcescens etc.) were selected, in order to study on the function of microbial ecosystems for the wastewater treatment process. Moreover, it was shown that the T-RFLP method was a useful molecular biological tool for the analysis on complex microbial ecosystems in wastewater treatment systems.The mixed culture experiments with aquatic rotatoria, Philodina sp. and isolated bacteria from some Johkasous were performed. It was shown that Philodina sp. was very effective to make high transparent water by the filtration effect and the coagulation effect of Philodina sp.. Moreover, we obtained the result that mineralization of organic carbon under the condition of predation for bacteria by Philodina sp was faster than it under the monoculture condition of bacteria. Also, total amount of decreases of DOC and TOC was enhanced by the existence of Ciliata T.thermophila. in the mixed culture system with bacteria as a microcosm system with a simple detritus food web structure. On the other hand, the numerical analysis of a simple predator-prey model drew out the result of contradiction to our experimental results. That is, our experimental results strongly suggest that existence of predator such as protozoan and/or metazoan increase the activity of bacteria for decomposition of organic matter, because the simple predator prey interaction between bacteria and protozoa only causes decrease of bacterial population as decomposer of organic matter.