The diversity of prokaryotes and fungi hosted in crude oils.

The diversity of prokaryotes and fungi in crude oils has not been understood clearly, though unique microbial communities may be hosted in crude oil. This study investigated the chemical compositions and microbial communities of crude oils from Henan, Bamianhe, and Jianghan oilfields of China. Statistical analysis revealed significant variations of both prokaryotic and fungal communities (P < 0.05) within different oilfields and oils with different biodegradation levels. Diversity analysis showed little difference in prokaryotic, but a significant difference in fungal (P < 0.05). Prokaryotic diversity was higher in heavily biodegraded oils than those in unaltered and slightly biodegraded oils; the opposite was true for fungal diversity (P < 0.05). Moreover, thermophilic prokaryotes were detected mainly in biodegraded heavy oils produced by the practice of thermal recovery from Henan and Bamianhe oilfields, and halophilic prokaryotes were detected mainly in oils from sandstone reservoirs containing hypersaline formation water from Jianghan Oilfield. Accordingly, microbial communities in oils are affected by oil biodegradation, extraction practices, and natural environments of native inhabitants in subsurface petroleum reservoirs.IMPORTANCEThe biological activities of endogenous microorganisms in crude oil play an important role in the production and development of crude oil. Although there have been many microbiological investigations of crude oil-contaminated sites, our understanding of the phylogenetic diversity, metabolic capabilities, and community dynamics of microbial communities within crude oil is far from complete. In this paper, the prokaryotic and fungal communities of three oil fields in different regions of China were analyzed, and several factors affecting microbial degradation were further identified. This study provides a new direction for the subsequent investigation of microbial activities inside crude oil.