[Microbial community structure analysis of unexploited oil and gas fields by PCR-DGGE]

Microbial communities of different depths (30, 60, 100, 150, 200cm) from the unexploited oilfield, gas field and control area were studied by PCR-DGGE and sequencing methods. The objectives of this study were to understand the microbial distribution in the regions of unexploited oil and gas fields, and to investigate the potential microbial indicators of oil and gas resources. The results showed that the Dice coefficients between different depths were very low (26-69.9). The microbial communities in the soil of 150 cm and 200 cm depth had greater richness (S > or = 19), diversity (H > or = 2.69) and evenness (E > or = 0. 90). The results of sequencing demonstrated that the bands from oilfield were mainly grouped into alpha-Proteobacteria, gamma-Proteobacteria, Actinobacteria, Acidobacteria with the predominance of gamma-Proteobacteria (75%). Most of the bands were related to oil-associated and hydrocarbon degrading bacteria, such as Methylophaga and Alcanivorax. While the gas field had alpha, beta, gamma, delta-Proteobacteria and Bacteroidetes, and gamma-Proteobacteria accounted for only 24%. More strains showed relativity to methanotrophs, such as Methylocystaceae. Thus, 150 cm and 200 cm were more suitable as the oil-gas exploration sampling depth. Methylocystaceae may act as potential indicators for gas resources, Methylophaga and Alcanivorax for oil.