Effects Of Mercury On Growth And Genetic Diversity Of Anaerobic Fermentation Bacteria

The sources of mercury pollution in soil are very broad and are mainly divided into:mining development,industrial development and agricultural production.Bioremediation technology is a promising approach to removing heavy metals from the environment.Because they contain microbes that can tolerate high concentrations of heavy metals.The super-accumulated plants known as "professional savers" exhibit excessive accumulation of certain heavy metals.The microbial cell wall is composed mainly of polysaccharides,lipids and proteins.The microbial has many functional groups that can bind heavy metal ions,including carboxylate,hydroxyl,amino and phosphate.Microorganisms can bioremediate heavy metals in soil,sediments and water through biological processes.The highest concentration of mercury that can be tolerated by super-accumulated plants is 81 mg/L.Based on this,two strains resistant to high concentrations of mercury ions were screened.Both strains were identified as Klebsiella pneumoniae.The effects of different mercury pollution levels on the abundance and microbial community composition of fermenting flora were investigated by high-throughput sequencing.The main research contents are as follows:(1)Mercury-tolerant strains were screened from samples collected from the fermentation tank by mercury ion concentration gradient acclimation.Study on growth conditions of strain Hg-A by single factor variable method.Two strains with strong adaptability,Hg-A and Hg-B,were isolated by plate dilution coating.After the appearance,physiological,biochemical and PCR amplification tests,both strains were identified as Klebsiella pneumoniae The experimental results show that the optimal temperature range for the growth of strain Hg-A is 25-35℃,and pH range is 5.0-8.0.The optimum growth conditions were 5%inoculum,25℃,and pH 5.0.(2)The dilution curve of high-throughput sequencing results indicates that the number of samples is reasonable and the experimental results are accurate.Species abundance distribution curve and a diversity analysis showed that the microbial abundance and uniformity were better in samples with mercury contamination levels of 0 mg/L,6 mg/L,and 10 mg/L.The results of the difference analysis between the a diversity index showed that there were normal differences among the three groups of repeated samples,but the repeatability of the three groups was still good,and the experimental results were accurate.The Veen and Heatmap diagrams at the genus level indicate that low concentrations of Hg2+ contamination have no significant effect on microbial similarity and community composition.When the Hg2+ pollution level is 80 mg/L,the high concentration of Hg2+ pollution has a great influence on the similarity and community composition of microorganisms,causing non-directional variation of microbial species.According to the community analysis at the genus level,the microbial species abundance changed significantly with low concentration of Hg2+,and the microbial community composition was significantly reduced.The dominant genus was Escherichia.Anosim analysis,Metastats difference analysis,and LEfSE analysis showed that there were some repetitive differences between the three parallel experiments,and there was no significant difference,which met the requirements of parallel experiments.The three parallel experiments can accurately reflect the experimental results.The experimental results show that the difference of microbial community composition and species abundance is less correlated with the low level of Hg2+ concentration,and the correlation with the high level of Hg2+ concentration is greater.