Study On The Population Structure And Toxic Gene Expression Diversity Of Microbial Bacteria In Coastal Sediments By DEHP

Objective:Di(2-ethylhexyl)phthalate(DEHP)is an endocrine disruptor widely used as a plasticizer worldwide,causing serious environmental pollution problems.At present,research on the diversity of bacterial microbial populations by DEHP mainly focuses on soil,while there is a lack of research on the impact of DEHP on the structure of bacterial populations in marine sediments and the expression of bacterial toxicity genes.Therefore,under indoor simulation conditions,this article investigates the effects of exposure to different concentrations of DEHP on the diversity of bacterial community structure in marine sediment and the expression of toxic genes(TDH)of common pathogenic bacteria Vibrio parahaemolyticus in marine sediment,providing a scientific basis for objectively evaluating the ecological risk of DEHP on marine sediment microorganisms.methods:Expose coastal sediments to four concentration gradients of DEHP(0 mg/kg,1mg/kg,10 mg/kg,50 mg/kg),and take samples after completion of exposure on the7 th and 14 th days.Count sediment bacteria using plate dilution method,and analyze the impact of different concentrations of DEHP exposure on sediment bacterial count using one-way ANOVA method;16S r RNA high-throughput sequencing method was used to detect bacterial genes in contaminated sediment microorganisms,Kruskal Wallis nonparametric test was conducted for inter group data,and DEHP’s α Diversityβ The impact of differences in diversity and species composition.Selecting common opportunistic pathogenic bacteria Vibrio parahaemolyticus in marine sediments as experimental subjects,they were exposed to DEHP at four concentration gradients(0mg/L,0.1 mg/L,1 mg/L,and 5 mg/L).Samples were taken after 36 and 72 hours of cultivation,respectively.The plate counting method was used to count the growth of Vibrio parahaemolyticus.The real-time fluorescence quantitative PCR method was used to detect the expression level of the target gene for heat resistance direct hemolysin(TDH)of common bacteria Vibrio parahaemolyticus in sediment.Single factor analysis of variance was used to analyze the differences in the growth of Vibrio parahaemolyticus and the expression of TDH toxicity genes under different concentrations of DEHP exposure.results:1.DEHP has a certain degree of inhibitory effect on the number of bacteria in coastal sediments.In sediment bacteria,the overall inhibitory effect was observed between the 10 mg/kg and 50 mg/kg groups and the control group(P<0.05),but there was no significant difference between the 1 mg/kg group and the control group(P>0.05).2.α Diversity results show that DEHP exposure affects marine sediment bacteriaα Diversity has a certain impact.On the Shannon index and Simpson index,the richness and evenness of bacterial species in the sediment of the infected group were generally lower than those of the control group,but there was no statistically significant difference(P>0.05).There were statistical differences(P<0.05)between the 7 and 14 days at different exposure times.In terms of Chao1 and Ace indicators,there was no statistical difference between the groups exposed to different concentrations,but in the 50 mg/kg group,the values increased significantly over time.In Goods＿On the coverage index,the values do not differ significantly.3.β The diversity results showed that exposure to DEHP at different concentrations had an impact on the differences in bacterial species among groups.In the Anosim analysis results,R=0.313 and P=0.001,indicating that the inter group difference is greater than the intra group difference and has statistical significance;In the principal coordinate analysis,it was found that there were differences between groups among the various groups exposed to the virus(P=0.001).4.The results of population composition differences show that at the phylum level,DEHP can affect various bacterial phyla.During the 7-day exposure time,there was a statistical difference(P<0.05)between the exposure group and the control group in the Actinobacteriota,Campilobacterota,and gemmatimonada phyla,and the exposure group showed an inhibitory state;During the 14 day exposure period,there were differences in the Proteobacteria and Campilobacterota phyla between groups(P<0.05).Proteobacteria phyla showed an increase in the exposure group compared to the control group,while Campilobacterota phyla showed a decrease in the exposure group compared to the control group.5.DEHP showed a significant inhibitory effect on the number of Vibrio parahaemolyticus,with statistical differences(P<0.05)between the groups exposed to different concentrations and the control.As the concentration increased,the inhibitory effect became stronger,with a dose-effect relationship.However,there was no significant difference in the number of bacteria compared to the exposure time.The expression of TDH toxic genes in Vibrio parahaemolyticus exposed to a concentration of 5 mg/L was higher than the average expression in the control group,but there was no statistical difference(P>0.05).Conclusion:1.1.DEHP pollution can inhibit the growth of overall bacteria and Vibrio parahaemolyticus in marine sediments,and there is a certain dose-effect relationship.2.DEHP pollution is a factor that affects the diversity of sediment bacterial population structure,and can provide a scientific basis for evaluating the ecological risk of DEHP pollution on marine sediment microorganisms.3.DEHP has no effect on the expression of TDH toxicity genes in Vibrio parahaemolyticus,but it is worth continuous attention and research.