Ocean Drilling Program (ODP) revealed that huge amount of bacteria exists in subsurface environment which extends probably up to 1.5 km beneath the seafloor, and a recent study suggests that this extends in continental subsurface as well. A study in shallow aquifer shows that bacteria exhibit high activity under the environmental constraint. Dynamic interaction between microorganisms and the Earth will be soon unveiled, which may enforce us to rewrite evolution of life and its interaction with the development of the Earth environment.