I notice there are some references to the bacteria found in hydrothermal vents in this thread. However, there is one aspect to their biology that is not often mentioned (though it is sometimes hidden in the scientific vernacular concerning these critters). It could be relevant to your area of interest.
These anerobic bacteria represent a departure from the long-held principle that life on Earth is based on photosynthesis. For these bacteria the thermal energy of the Earth is their fuel for producing basic hydrocarbon material at the base of the food chain. You could call it a thermo-synthesis. The reason it can occur there (ocean bottom) is that the high pressure is necessary for the thermal energy "quanta" to have an energy sufficient to support the bonding of the hydrocarbon molecules (the way sunlight does for plants on the surface). Like plants, they need no oxygen for this process. They simply require water, CO2, heat energy, and probably hydrogen sulfide (as a catalyst, somewhat like chlorophyl).
When it comes to moving up to higher life forms, however, the catch is that they must have some medium to support them like the water or air. It is possible to discuss a few non-traditional life forms that are connected to such microbe processes. Consider the ice-covered moons of Jupiter, which would have enough water, a hot core (continuously energized by tidal forces), and all the basic elements for hydrocarbon formation. Or look at the subterranean levels of some of the other planets.
On Earth these bacteria probably work their little assets off in subterranean cavities making this slime-like hydrocarbon that eventually winds up as oil (following geothermal processing). That of course would mean oil is a continuously renewable resource, but that is another matter altogether.
