Differences in Geological Conditions Have Reshaped the Structure and Diversity of Microbial Communities in Oily Soils

High-throughput sequencing was used to study the microbial community structure and diversity changes in oil-contaminated soils under different spatial distances and environmental conditions. The results showed that 239 Phyla, 508 Classes, 810 Orders, 1417 Families, 2048 Genera, 511 Species of soil microbial communities were obtained from 16 samples in three regions. Petroleum hydrocarbon pollution has changed the physicochemical properties of the soil and the diversity and community structure of the original microorganisms. Alpha diversity results showed that the soil samples contained high bacterial diversity, especially in Qingyang’s loess soil samples. The bacterial abundance was in the order of loess soil>black soil>sandy soil. Beta diversity reveals that spatial distance limitations and random variation of replicate samples may be the main factors leading to differences in soil heterogeneity and microbial community structure. The dominant bacteria phyla with broad petroleum hydrocarbon degradation spectra such as Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were identified. Pseudomonas, Bacillus, Nocardioides, Oceanobacillus, Sphingomonas, Alkanindiges and Streptomyces were identified as functional hydrocarbons for the degradation of petroleum hydrocarbon pollutants. The microbial communities are co-exclusion under different geological conditions, and compete for the degradation of petroleum compounds in the soil through amino acid metabolism, energy metabolism and carbohydrate metabolism. The correlation analysis results using partial least squares path model (PLS-PM) exhibited that microbial diversity and petroleum hydrocarbon content were controlled by altitude factors which could affect not only soil factors but also environment temperature, and soil microbial diversity affected petroleum hydrocarbon content through positive effect on soil enzyme activity. This study can provide microbial strain resources and technical for repairing petroleum hydrocarbon contaminated soil.