Ecophysiology and genomics of key sulfate-reducing bacteria involved in anaerobic hydrocarbon degradation at marine gas and oil seeps

Abstract

The diversity, function and community structure of anaerobic hydrocarbon-degrading microorganisms in marine environments were elucidated by methods in molecular ecology, microbiology and microbial genomics. A high diversity of n-alkane degraders was revealed in globally distributed marine seep sediments based on genes encoding (1-methylalkyl)succinate synthase (MasD), the functional marker for anaerobic n-alkane degradation. Both abundant cosmopolitan and specialized variants of MasD were detected as well as novel lineages of n-alkane degraders. It could be shown that the community structure is clearly driven by the available hydrocarbon substrate. Further, the response of the microbial community in Caspian Sea sediments to simulated crude oil seepage using a Sediment-Oil-Flow-Through system was investigated. Sulfate reduction and methanogenesis were important processes in the anaerobic degradation of hydrocarbons during crude oil seepage in these sediments. After oil-flow-through, several groups of SRB exhibited an increase in cell numbers and are likely responsible for the observed decrease in aliphatic hydrocarbon concentration.