We are now facing with serious water crisis in the 21st century. Thus it is an urgent task for us to build a more balanced and sustainable society and also reserve the limited water resource. Our lab focuses on the clarification of the microbial processes that involved in various biogeochemical cycles, which is ocurring in both natural aquatic environments and manipulated water treatment systems. We believe understanding the ecological characteristics of functional microorganisms is a fundamental step for us to maintain a healthy water environment.