Changes Of Groundwater Microbial Community Under Organic Pollutants And Salinity Stress And Research Of Soil Remediation By Bacillus Subtilis YL4

In Shanghai,the environment of groundwater is threatened by salt stress and organic pollution,which may affect the composition of microbial community in the groundwater system in this area with time.In this study,the indexes of organic pollution and salt concentration of groundwater were investigated.All the samples had organic pollution and salt stress,which was more serious in normal period than in high water period.In the environment of groundwater,the structure of microbial community changes dynamically with time and space.The increase of organic pollutants had a negative impact on almost all microbial groups,and the increase of salt stress had a greater impact on the other groups except Firmicutes and Proteobacteria.Some potential pathogenic bacteria had been discoveried,which indicated that there may be pathogenic bacteria contamination in groundwater.A strain with strong environmental tolerance was isolated from samples and named Bacillus subtilis YL4.Under the salt stress represented by 0.6%Na Cl,the inoculation of 1×10~6CFU/m L Bacillus subtilis YL4 effectively alleviated the environmental stress.In view of the severe trend of land salinization in the Yangtze River Delta region and the excellent performance of YL4 under salt stress,it was expected that YL4 could be used as a potential and effective biological inoculant to enhance plant resistance to environmental abiotic stress and increase yield.By adding a certain proportion of biological excipients to the conventional soil,the addition of Bacillus subtilis YL4 significantly improved the growth of green vegetable plants under salt stress,and the introduction of exogenous calcium ions also stimulated the increase of plant biomass.Calcium phosphate was identified as the source of exogenous ions,combining with the ability of Bacillus subtilis YL4 to dissolve inorganic phosphorus,without the aggravation of salt stress caused by the introduction of soluble ions.Under salt stress,the effect of biological excipients,Bacillus subtilis YL4 and calcium phosphate on the growth of seedlings was very significant.