The Shifs Of Sediment Microbial Community Phylogenetic And Functional Structures During Metal Reduction And Isolation Of Metal Resistance Strain In Lanzhou Reach Of The Yellow River

Lanzhou reach of the Yellow River, located in the upstream of the Yellow River, have been contaminated by heavy metals and polycyclic aromatic hydrocarbons. We hypothesized that indigenous microbial communities have developed their strategies to adapt to such environmental conditions. Sediment samples were collected from two nearby sites (site A and site B) along the Yellow River and incubated with hexavalent chromium (Cr (VI)) at37℃for30days. And We also isolated a strain named Lzu-02from the sediments which is able to resist Hg (II). Cr (VI) reduction was only observed with site A sediment samples. Both functional gene array (GeoChip4.0) and454pyrosequencing of16S rRNA genes were used to analyze the composition, structure, and functional potentials/activities of microbial communities after30-day incubation with Cr (VI). GeoChip data showed that genes involved in carbon and nitrogen cycling, and metal resistance had been significantly (p<0.05) increased after30-day incubation with Cr (VI) only in site A sediment samples.454pyrosequencing analyses revealed that Thiobacillus populations increased from0.9%to43.7%after30-day incubation with Cr (VI) in site A sediment samples. The divergence of Cr (VI) reduction between these two sediment samples might be due to the difference in concentrations of sulfur and carbon sources. Several Cr (VI) resistance and reduction bacteria closely related to Staphylococcus aureus and lysinibacillus identified by16S rRNA gene sequences were isolated from site A sediment samples.Lzu-02was able to reduce Hg (II) to elemental Hg aerobically when incubated in M9medium with40μM HgCl2. The optimum condition of resisting and reducing Hg (II) for Lzu-02was pH6and37℃. Lzu-02was identified to be most similar to Staphylococcus epidermidis by16S sequencing analysis and Vitek phenotype identification. We also found that Lzu-02had a mer operon consisting of SmerR, SmerC, SmerT and SmerA genes. The relative expressions of three genes(SmerC, SmerT and SmerA) were upregulated when Lzu-02was cultivated in M9medium with40μM HgCl2. These bacteria were used for further analysis of their bioremediation potential. This study is the first report about Lanzhou reach soil microbial community, and provides useful information about Cr (Ⅵ) and Hg (Ⅱ) reduction mechanisms and possible strategies for bioremediation of contaminated sites in Lanzhou reach of the Yellow River.