[en] The current concept for the functioning of high-level radioactive waste repositories assumes that redox conditions will remain reducing even after repository closure. Oxidizing conditions may, however, develop in and around the waste cavern due to inorganic and/or organic redox reaction during the construction and the operational phase. Within the redox reaction, several kinds of oxides and hydroxides are inevitably formed and believed to have a strong influence on elemental migration and retardation through adsorption and/or co-precipitation in the near-field (NF) environment, where their formation is certainly influenced by microbial activity. Such oxidized zones can be formed at the interface between the engineered barrier system and surrounding host rock and will affect the efficiency of the safety barrier after closure of the repository. The influence of the interaction between microbes, water and rock around waste caverns is therefore important in understanding long-term chemical stability, elemental migration, and hence the safety of proposed sites for deep geological isolation of radioactive waste. However, the complex reaction among groundwater, rock/minerals including synthetic materials and microbes under deep geological environments is not well understood and is thus not sufficiently taken into account in present safety case development. Here, we therefore try to describe the role of microbes in the repository system in our geological regime and deep geological environment for both cases of sedimentary and crystalline rocks. This kind of discussion can also be used for the planning of Underground Research Laboratory's (URL) study relevant to microbial influence in NF environment for the development of realistic long-term safety of radioactive waste repositories in Japan. (author)