Molecular detection and microcalorimetric analysis of soil microbial community along an oil contamination gradient

To better understand the microbial diversity and activity under crude oil contamination, denaturing gradient gel electrophoresis fingerprinting, real-time PCR and micro-calorimetric analysis were applied in this study. Principal component analysis (PCA) was performed to detect the greatest contributors to variation among oil-contaminated soil samples. Furthermore, Pearson's correlation was adopted to determine correlations among microbial diversity, microbial activity and geochemical factors. It found that microbial diversity index (H) showed a decrease along the oil contamination gradient, while the abundance of bacteria and actinobacteria also presented a decreasing trend in the range from 4.1×10⁷ to 1.4×10⁵ copies g^-1 and from l. 1×10⁶ to 1.6×10³ copies g^-1, respectively. And Proteo-bacteria, Actinobacteria, Chloroflexi, and Acidobacteria were the dominant bacteria in the most contaminated soil. Crude oil, organic matter, soil available nitrogen and phosphorus were found to be the vital factors influencing the microbial community structure. PCA analysis indicated that crude oil contamination could lead to the imbalance of soil ecosystem. Our work offers an insight into microbial diversity and activity in oil-contaminated soils, providing potential applicable information for environmental assessment.