Deep-dwelling microbes play a significant role in the formation and degradation of oil. They contribute to the breakdown of organic matter into hydrocarbons, which can eventually become oil. As indicated by the article from Live Science, these microbes generally get passed up and fall to the seafloor, where they become buried under layers of sediment and are eventually cooked into petroleum. The New York Times article highlights that as subsurface microbes break down rock, they often free metals stuck within it and release chemicals like hydrogen.
Research has shown that oil-dwelling bacteria are social creatures in Earth's deep biosphere, as mentioned in a study reported by Phys.org. They can consume some toxins, but the worst remain, according to the study. Abiogenic hypotheses propose that oil and gas may originate from deep carbon deposits, present in the Earth's mantle, rather than solely from fossil deposits, as stated on Wikipedia.
The process of oil formation begins in warm, shallow oceans with the accumulation of dead organic matter, which is then subjected to heat and pressure over millions of years, as explained by Energy Education. Deep intraterrestrial microbial life is also under exploration, with a focus on various deep habitats, as reviewed in an article by the academic journal FEMS Microbiology Letters.
In summary, deep-dwelling microbes are integral to the complex process of oil formation, both through their role in breaking down organic matter and potentially contributing to the abiogenic origin of oil.