Subsurface Petroleum Microbiology

Abstract

The importance of microbial activities in petroleum oilfields and reservoirs has been recognized for a long time, but our knowledge of the diversity of bacteria growing in these ecosystems and their metabolic activities in situ is still limited. Petroleum biotransformations in near surface or subsurface environments are achieved by either aerobic or anaerobic microorganisms, depending on oxygen input or the presence of other electron acceptors and appropriate nutrients. Biodegradation of hydrocarbons by aerobic bacteria is supported by the presence of oxygen, whereas anaerobic heterotrophic microorganisms requiring nitrate, sulfate, iron, manganese or carbon dioxide as electron acceptors are responsible for biodegradation of hydrocarbons in the absence of oxygen. In fermentative conditions, no external oxidants are used for substrate oxidation, so that no net oxidation–reduction occurs. More recent research suggests that the anaerobic degradation processes dominate subsurface sedimentary environments, despite slow reaction kinetics. An overview of our current knowledge on the near-and subsurface microbiology associated with petroleum and biogeochemical processes is provided in this chapter.