The Isolation And Identification Of Methyl-Hg-converting Bacteria

It is representative for the natural Hg, smelted Hg and exhausted Hg in the inland. Mine rejectamenta and the bio-accumulation effect special for Hg element have brought great threat to the around ecosystem, the health of local residents.Compared study had been made in this research with the material of paddyfield soil from the diggings of Wanshan region, aiming at the toxic effect from Hg in soil. The total number of microbes in the sample is decreased owing to toxicity of Hg, and the order of their sensitivity to Hg is Actinomyces > Bacteria> Fungi. Additionally, the Hg containing in soil decreased the number of microbial physical categories. In the circumstance containing high concentration of Hg, the influence is very obvious for the bacterial physical community which take part in the cycle of nitrogen element, the bacterial community which take part in the carbon element cycle is less obvious, namely, nitrobacteria> free-living nitrogen fining bacteria>ammonifying bacteria> cellulose-decomposing bacteria. The result shows that heavy metal Hg can inhibit soil microflora, the Hg contamination in Wanshan region is very serious. The number of actinomyces sensitive to Hg can be used as a eco-index for the degree of soil contaminate.In addition, 68 strains are isolated in the research, one can endure 0.1mg/L, and 12 strains can endure 5mg /LHg. Most of the strains are G+, bacillus. And the facultative can endure higher Hg, which can grow in the medium containing 5mg/L Hg. 12 strains are detected for plasmid, and 7 strains are found. Those strains carrying plasmid have an ability to endure higher Hg concentration, meaning that plasmid is important for the ability to endure Hg.A strain DT, which can convert Hg into mercury methylation is isolated from paddyfield soil. After domestication, DT can grow well in the medium containing 25mg/LHg. Research shows that, the growth cycle of strain will delay in the circumstance existing higher concentration of Hg; however, lower concentration of Hg can stimulate the growth of strain. Temperature, PH value and the salinity can also influence the mercury methylation of bacteria, the optimal condition for mercury methylation of bacteria is pH5.0, 35°C, 10mg/L Hg²⁺.The thesis provides some basic materials for further research on the mechanism of mercury methylation of DTstrain, sequentially, giving the theoretical basis for the microbe-participated Hg-cycle. These researches have important sense for the understanding of the Hg existing form in the body of microbes.