Enrichment and Characterization of a Psychrotolerant Consortium Degrading Crude Oil Alkanes Under Methanogenic Conditions.

Anaerobic alkane degradation via methanogenesis has been intensively studied under mesophilic and thermophilic conditions. While there is a paucity of information on the ability and composition of anaerobic alkane-degrading microbial communities under low temperature conditions. In this study, we investigated the ability of consortium Y15, enriched from Shengli oilfield, to degrade hydrocarbons under different temperature conditions (5-35 °C). The consortium could use hexadecane over a low temperature range (15-30 °C). No growth was detected below 10 °C and above 35 °C, indicating the presence of cold-tolerant species capable of alkane degradation. The preferential degradation of short chain n-alkanes from crude oil was observed by this consortium. The structure and dynamics of the microbial communities were examined using terminal restriction fragment length polymorphism (T-RFLP) fingerprinting and Sanger sequencing of 16S rRNA genes. The core archaeal communities were mainly composed of aceticlastic Methanosaeta spp. Syntrophaceae-related microorganisms were always detected during consecutive transfers and dominated the bacterial communities, sharing 94-96 % sequence similarity with Smithella propionica strain LYP(T). Phylogenetic analysis of Syntrophaceae-related clones in diverse methanogenic alkane-degrading cultures revealed that most of them were clustered into three sublineages. Syntrophaceae clones retrieved from this study were mainly clustered into sublineage I, which may represent psychrotolerant, syntrophic alkane degraders. These results indicate the wide geographic distribution and ecological function of syntrophic alkane degraders.