Prokaryotic population of a tar lake Amplicon library. aquatic metagenome

Anaerobic microbial degradation of hydrocarbons influences the quality of oil resources and can lead to the generation of highly viscous bitumen. Previous work suggests such biodegradation mostly occurs at the interfaces of oil and water compartments. However, we show at the example of the world’s largest asphalt lake in Trinidad Tobago that microorganisms thrive in water droplets (1-5 µl) entrapped in oil. The water inclusions originate from deep subsurface formations and harbored complex methanogenic microbial communities actively degrading oil indicated by metabolites derived from oil-hydrocarbons. The large surface area of the water droplets associated with the 13,5 % water content of the oil reveals a currently underestimated potential for biodegradation of oil resources and an intriguing new and extreme habitat for microbial life in oil.