Hydrothermal vent microbial communities
The hydrothermal vent microbial community includes all unicellular organisms that live and reproduce in a chemically distinct area around hydrothermal vents. These include organisms in the microbial mat, free floating cells, or bacteria in an endosymbiotic relationship with animals.
Source: Wikipedia — Hydrothermal vent microbial communities (CC BY-SA 4.0)