Subsurface lithoautotrophic microbial ecosystem
Subsurface lithoautotrophic microbial ecosystems, or "SLIMEs" (also abbreviated "SLMEs" or "SLiMEs"), are a type of endolithic ecosystems. They are defined by Edward O. Wilson as "unique assemblages of bacteria and fungi that occupy pores in the interlocking mineral grains of igneous rock beneath Earth's surface." Endolithic systems are still at an early stage of exploration.
Source: Wikipedia — Subsurface lithoautotrophic microbial ecosystem (CC BY-SA 4.0)