The bottom of the deep sea is a desert just like the Sahara. It's a dark and cold place, so dark that no organism can use photosynthesis to grow and become food to other organisms. You might know that most life on our planet is sustained by photosynthesis - the fixation of carbon dioxide by plants, algae and other photosynthetic organisms, using sunlight. Therefore, one might say that all life on Earth is ultimately supported by the energy coming from the sun. In the absence of sunlight and plants, the animals living in these deep-ocean resorts can be anything but vegetarians.
Bacteria play there the same role as plants on terra firma - the role of primary producers.
Instead of using light, these bacteria use chemical energy to fix carbon for growth. Some of these amazing microbes live inside animals such as vestimentiferan tube worms and giant clams. Other 'sulfide-loving' bacteria prefer to live a free life in the water around vents or at the surface of rocks and organisms in the neighborhood. These little bugs can then be grazed by animals like snails, limpets and some polychaete worms , which in turn are eaten by carnivores like spider crabs and nereid worms. The exact way these unusual types of food webs work is still a mystery.