F. The type of microbes found under the surface depends on the subsurface environment. Bacteria thrive in most sedimentary rocks, which contain organic compounds that nourish them. These nutrients were originally produced by plants at the surface, before the sands, silts, and clays that make up most sedimentary rocks were buried and consolidated into solid rock. Scientists also found that microorganisms can live in igneous rocks such as basalt where little organic material is available. The reason they can survive is because they are autotrophs, organisms that synthesize organic compound from inorganic sources.
Scientists estimate some microbial communities to be millions of years old.
Of the small percentage of microorganisms that have been examined, a large amount of them have shown valuable capabilities, such as, the ability to degrade toxic organic compounds, the production of antibiotics, heat stable enzymes and novel pigments. Many positive results will surely come from these microorganisms. They may even show us how life functioned before photosynthesis evolved. Microorganisms are essential for all life because they decompose waste. If it were not for decomposers, elements that are essential to life would be locked up in dead animals and feces.