Responses of rhizosphere microbial community structure and metabolic function to heavy metal coinhibition.

Metal mineral mining results in releases of large amounts of heavy metals into the environment, and it is necessary to better understand the response of rhizosphere microbial communities to simultaneous stress from multiple heavy metals (HMs), which directly impacts plant growth and human health. In this study, by adding different concentrations of cadmium (Cd) to a soil with high background concentrations of vanadium (V) and chromium (Cr), the growth of maize during the jointing stage was explored under limiting conditions. High-throughput sequencing was used to explore the response and survival strategies of rhizosphere soil microbial communities to complex HM stress. The results showed that complex HMs inhibited the growth of maize at the jointing stage, and the diversity and abundance of maize rhizosphere soil microorganisms were significantly different at different metal enrichment levels. In addition, according to the different stress levels, the maize rhizosphere attracted many tolerant colonizing bacteria, and cooccurrence network analysis showed that these bacteria interacted very closely. The effects of residual heavy metals on beneficial microorganisms (such as Xanthomonas, Sphingomonas, and lysozyme) were significantly stronger than those of bioavailable metals and soil physical and chemical properties. PICRUSt analysis revealed that the different forms of V and Cd had significantly greater effects on microbial metabolic pathways than all forms of Cr. Cr mainly affected the two major metabolic pathways: microbial cell growth and division and environmental information transmission. In addition, significant differences in rhizosphere microbial metabolism under different concentrations were found, and this can serve as a reference for subsequent metagenomic analysis. This study is helpful for exploring the threshold for the growth of crops in toxic HM soils in mining areas and achieving further biological remediation.

Role of tailing colloid from vanadium-titanium magnetite in the adsorption and cotransport with vanadium.

The geochemical cycling of vanadium (V) in mining areas has attracted much attention. However, little knowledge was about the effects of tailing colloids on the fate and transport of vanadium in tailing reservoirs which was ignored before. This study investigated the interactions of tailing colloids from vanadium-titanium magnetite with vanadium. Colloid characterization, tailing leaching, adsorption, and column experiments of single and cotransport of tailing colloid with V were conducted. Results show that 98.08% V in the vanadium-titanium magnetite tailing was in the residual state with limited leachable V under various conditions. The adsorption of V to the tailing colloid was via electrostatic attraction and surface complexation on the heterogeneously distributed sorption sites on the colloid surface. The adsorption control step was the diffusion of V into the tailing colloid pores. The increase in pH and the decrease in ionic strength (IS) promoted the single transport of tailing colloid and V in quartz sand columns. In cotransport scenarios, V promoted the transport of tailing colloids via the surface coating effect. In contrast, the transport of V was retarded by the adsorbed tailing colloid on the quartz sand surface. The pre-adsorbed V in the column enhanced the subsequent transport of tailing colloids by electrical repulsion, while the pre-adsorbed tailing colloids facilitated the subsequent transport of V via cotransport of the released colloids with V. The high mobility of the tailing colloid and V and their cotransport in the porous media highly demonstrated the potential V pollution pathways that need to be taken into account.

[Expression and purification of GST-Rta fusion protein from EB virus and preparation of the polyclonal antibody against GST-Rta].

OBJECTIVE: To obtain the recombinant fusion proteins GST-Rta185 and GST-Rta150 from EB virus and prepare two Rta protein specific polyclonal antibodies, respectively. METHODS: Plasmids pGEX-R1501, pGEX-R1851 and pGEX-5X-3 were separately transformed into Escherichia coli BL21 (DE3). Expressions of the recombinant proteins R150-GST, R185-GST and free GST were induced by 0.1 mmol/L IPTG in LB medium. The expressed proteins were purified from lysates with Glutathione Sepharose 4B. Purified proteins were mixed with Freund's adjuvant and then were used to immunize rabbits. RESULTS: High levels of expression of target proteins were detected in the lysates and the purified proteins were obtained by affinity chromatography with Glutathione Sepharose 4B. Western blot and ELISA analysis suggested that the polyclonal antibodies against GST-R185 and GST-R150 were specific. CONCLUSION: The antiserums have good specificity. They are important for the research on Rta fusion proteins from EB virus and for the diagnosis or treatment of EB virus associated diseases.