Propionate metabolism and diversity of relevant functional genes by in silico analysis and detection in subsurface petroleum reservoirs.

Propionate is a common metabolic intermediate occurring in environmental samples including petroleum reservoirs. Available microbial genomes were obtained from the NCBI database and analyzed in silico by hmmscan to check three metabolic pathways of propionate production in petroleum reservoir systems. The succinate pathway was the dominant one while the other two (lactate and 1,2-propanediol pathways) contributed less to the formation of propionate according to the Hidden Markov Model calculation. The mmdA gene encoding methylmalonyl-CoA decarboxylase was used as a biomarker gene to detect the diversity of microbes involved in the propionate formation in Jiangsu oil reservoirs. The mmdA gene clone library showed that microbes affiliated within the genus of Archaeoglobus, Thermococcus, Anaerobaculum, as well as more than ten other genera were the potential microorganisms involved in the production of propionate. Meanwhile, as the biomarker genes involved in the other two propionate-producing pathways, the functional genes of lcdA and pduP were tested with PCR amplification, but no positive results were observed in Jiangsu oil reservoirs.