| With the rapid development of modern industry,oil and its derivatives are used as industrial raw materials in various industries,and oil is often leaked during production,transportation,and storage,which poses a serious ecological hazard.The many oil fields and the frequent transport of oil from ports in the coastal area have caused serious pollution to the water environment and wetland soils in the coastal area.And through bioremediation technology,can be used for pollution treatment in a large area,with the advantages of low price and little secondary pollution,so the use of plants,microorganisms,and combined remediation technology to remediate oil-contaminated soil has a very broad development prospect.Among them,microbial-phytoremediation is an emerging bioremediation technology that can achieve efficient degradation of total petroleum hydrocarbons(TPH)by introducing petroleum-degrading bacteria and oil-tolerant plants into petroleum-contaminated soils.In this study,the highly efficient petroleum-degrading bacteria Acinetobacter sp.Tust-DM21 was immobilized and combined with the oil-tolerant plant Suaeda glauca as the co-remediation subject in the Tianjin Binhai area.The study investigated the remediation effect of the combined remediation on oil-contaminated soil,the changing pattern of the soil community,the interaction between exogenous petroleum-degrading bacteria,PGPR,and indigenous bacteria,and the degradation pathways of petroleum hydrocarbons in the combined remediation.In this study,natural attenuation(NA),microbial remediation(MR,using Acinetobacter sp.Tust-DM21),phytoremediation(PR,using Suaeda glauca),and microbial-phytoremediation(MPR,using both species)were used to degrade petroleum hydrocarbons for a 32-day remediation period.We evaluated the degradation effects of the four different bioremediation methods,using the rate of degradation of total petroleum hydrocarbons in the soil,the relevant enzyme activities of the soil(soil dehydrogenase,soil peroxidase,soil urease,soil lipase),and indicators of plant resistance(plant chlorophyll content,plant proline content)as assessment indicators.After the restoration was completed,TPH was significantly degraded by the remaining three restoration methods compared to natural restoration(NA),in the order of MPR(46.05%)> MR(27.52%)>PR(21.88%)> NA(5.62%).The soil enzyme activities of all four remediations were significantly higher in MR,PR,and MPR than in NA after the completion of remediation.Soil urease and soil catalase had the highest enzyme activities during PR,while soil dehydrogenase and soil lipase had the highest activities during MPR.The measurement of plant stress resistance indicators showed that the plant height,chlorophyll content,and proline content of the MPR plants were higher than those of the PR,and the stress resistance was enhanced compared to the PR.The results suggest that MPR can be used more effectively as a remediation technique for petroleum-contaminated soils.Using 16 S high-throughput sequencing,soil samples from different bioremediation were analyzed and the results showed that in the α-diversity analysis,the alpha diversity indices of MPR and MR were higher than PR among the three bioenhanced remediation methods,indicating that Suaeda glauca transplanted with indigenous bacteria had a competitive effect reducing the microbial diversity in the soil,but inoculation with Tust-DM21 maintained the soil’s bacterial.The MPR combined the advantages of both.The results in the β-diversity analysis showed that the microbial community structure was significantly different in PR and MPR compared to NA and that the soil microbial community structure was altered,with Suaeda glauca significantly influencing the soil microbial community structure.At the bacterial phylum level structure,the phylum Actinobacteria dominated in NA,while the phylum Proteobacteria dominated in the remaining three biofortified restorations.The phylum level was then analyzed and found to be dominated by the Alphaproteobacteria and Gammaproteobacteria in MR,PR,and MPR.Finally,analysis at the soil bacterial genus level revealed a large increase in PGPR in MPR,and correlation analysis between Tust-DM21 and PGPR showed that Acinetobacter was associated with Pseudomonas,Lysobacter,Parasegetibacter,Qipengyuania,Sphingopyxis,Skermanella,and unidentified-Acidobacteria were positively correlated,stimulating the growth of these genera.Further tests for significant differences between MR,PR,and MPR at the genus level revealed that MPR combined the dominant effects of both compared to PR and MR,with a significant increase in the number of differential genera.In addition,genetic prediction of microbial community function revealed that the abundance of genes in the degradation pathway of PAHs in MPR was also increased compared to MR and PR.This study shows that the soil microbial community structure was reconstructed in the MPR with a significant increase in petroleum-degrading bacteria and plant inter-rhizosphere promoting bacteria and that these genera regulated soil enzyme activity,increased the abundance of functional genes in the petroleum hydrocarbon degradation pathway,and accelerated the dissipation and degradation of TPH in petroleum-contaminated soil,revealing the molecular degradation mechanisms in the combined microbial-phytoremediation.These contribute to a better understanding of the degradation pathways and molecular remediation mechanisms of the combined microbial-Phyto strategy and provide new strategies for the remediation of petroleum contamination in saline soils in coastal areas. |
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