Increased exploitation and use of petroleum resources is leading to increased risk of petroleum contamination of soil and groundwater. Although phytoremediation is a widely-used and cost-effective method for rehabilitating soils polluted by petroleum, bacterial community structure and diversity in soils undergoing phytoremediation is poorly understood. We investigate bacterial community response to phytoremediation in two distinct petroleum-contaminated soils (add prepared petroleum-contaminated soils) from northwest China, Weihe Terrace soil and silty loam from loess tableland. High-throughput sequencing technology was used to compare the bacterial communities in 24 different samples, yielding 18,670 operational taxonomic units (OTUs). The dominant bacterial groups, Proteobacteria (31.92%), Actinobacteria (16.67%), Acidobacteria (13.29%) and Bacteroidetes (6.58%), increased with increasing petroleum concentration from 3000 mg/kg–10,000 mg/kg, while Crenarchaeota (13.58%) and Chloroflexi (4.7%) decreased. At the order level, RB41, Actinomycetales, Cytophagales, envOPS12, Rhodospirillales, MND1 and Xanthomonadales, except Nitrososphaerales, were dominant in Weihe Terrace soil. Bacterial community structure and diversity in the two soils were significantly different at similar petroleum concentrations. In addition, the dominant genera were affected by available nitrogen, which is strongly associated with the plants used for remediation. Overall, the bacterial community structure and diversity were markedly different in the two soils, depending on the species of plants used and the petroleum concentration.

MiSeq high-throughput sequencing methods were used to study the bacterial diversity and community structure composition of Pb-Zn tailing soils in the Qinling Mountains (in the case of Bijiashan and Yanzibian), and to analyze their correlation between soil chemical properties and heavy metal concentrations. The differences between the two mine tailings were compared to summarize and analyze the main influencing factors on the soil bacterial community structure of the tailings. The results showed that the soils of the two tailings were polluted by heavy metals to different degrees, and the polluted degree of the tailings in Bijiashan was significantly higher than that of Yanzibian. Proteobacteria, Actinobacteria, Acidobacteria, Chlorella, and Firmicutes were the main dominant phyla in tailing soils. Specifically, the relative abundance of bacterial communities of Proteobacteria and Acidobacteria in the polluted soil showed a general upward trend compared with the control. On the contrary, the relative abundances of Actinobacteriota and Chloroflexi showed a decreasing trend in the contaminated soil compared with the control. Redundancy analysis (RDA) and Variance Partitioning Analysis (VPA) showed that soil chemical properties and heavy metal concentrations affected bacterial community structure jointly. Specifically, soil organic matter (SOM), total organic carbon (TOC), total potassium (TK), total phosphorus (TP), and total nitrogen (TN) are the positive influencing factors of bacterial community structure, while heavy metals Cd, Pb, Zn, Cu is a negative factor affecting bacterial community structure. We further concluded that the main influencing factors of tailing soil bacterial community structure were pH, SOM, TN and heavy metals Cd, Zn, and Pb. In addition, the effects of heavy metal contamination did not exceed the effects of soil physicochemical properties on tailing soil bacterial community structure in these two tailings.

Phytoremediation is a promising bio-technology where plants associated with microbes are employed to remediate sites co-contaminated with petroleum. With the in-depth study of plant restoration, it is necessary to explore the dynamic changes of microbial communities in petroleum-contaminated soil. This study investigated the effects of Ryegrass on bacterial community and diversity in petroleum contaminated soil. High-throughput sequencing technology was used to compare the bacterial communities in 14 groups samples at different repair stages. It was concluded that different responses were observed to promote or inhibit microbial reproduction. The most significant bacterial family were Comamonadaceae, Nocardiaceae, Blastocatellaceae, and Cytophagacea. Comamonadaceae showed the highest level of remediation in non-petroleum-contaminated soils at 90 days. However, Blastocatellaceae and Cytophagaceae exhibited high microbial contents in petroleum-contaminated soil at 0 and 40 days, respectively. In all samples, plants improved the remediation of petroleum-contaminated soil and the highest abundance of microbial communities were found after 90 days. These data indicate that not only rhizosphere secretions but also petroleum, will promote microbial growth. Moreover, the repair time has a vital effect on microbial community changes. This study supports the foundation to control soil pollution and highlight the periodic dynamic of microbial community diversity and structure.