Pollution pressure and soil depth drive prokaryotic microbial assemblage and co-occurrence patterns in an organic polluted site.

Organic polluted sites have become a global concern of soil contamination, yet little is known about microbial vertical distribution and community assembly in organic polluted sites. Here, high-throughput sequencing technology was employed to investigate prokaryotic microbial diversity and community assembly along soil profile in an abandoned chemical organic contaminated site. Results showed that there was no significant difference (P > 0.05) observed in microbial alpha diversity among different soil layers, whereas the structure of microbial communities presented significantly different (P < 0.05) in the superficial layer (0-0.5 m) compared with intermediate (1-1.5 m) and bottom (2.5-3 m) layers. Soil prokaryotic microbial community evolved to possess the potential of degrading organic pollutants under long-term organic pollution stress. A relatively homogeneous environment created by the organic polluted site mainly induced the ecological process of homogeneous selection driving community assembly, while dispersal limitation gained importance with the increase of soil depth. Organic contaminants were identified as the key driver of destabilizing co-occurrence networks, while the frequent cooperative behaviors among species could combat organic pollution stress and sustain prokaryotic community stability. Collectively, pollution pressure and soil depth jointly affected prokaryotic microbial assemblage and co-occurrence that underpinned the spatial scaling patterns of organic contaminated sites microbiota.