| The soil is one of the most important natural resources to the survival of human, which has an important significance to the ecological environment quality and human health. Due to the emerging environmental issues related to heavy metals, concern about the soil quality of farming lands near manufacturing district is increasing. Soil pollution had an adverse effect on human, not only can directly lead to the decrease of food production, but also can affect human health by the food chain. In addition, the pollutants by groundwater and soil pollutants transfer exert human multiple adverse stress and damage on human. Investigating the function of soil microorganisms exposed to long-term heavy metal contamination is meaningful and important for agricultural soil utilization.In this paper, the research included the following two parts. Arable fresh soils used in experiment were sampled near industrial factories(Xia Wan Gang areas) in Hunan Province, Zhuzhou city. Firstly, taking fresh arable soil as objection,the aim was to selected high Cd2+ tolerance bacteria and fungi strains and to identify the species. Soil samples were diluted according a series dilution concentration gradient from 10-1 to 10-5. Two different medians, including bacteria and fungi culture medium, were used to domesticate the tolerance of soil rhizosphere microorganisms to heavy metals and cultured keeping constantly temperature in the water bath oscillator. Liquid culture mediums with highest Cd2+ tolerance were selected as the bacteria and fungi source, respectively. Then plate streaking on the plate medium was for separation of strains(both bacteria and fungi). The pure strain will be observed in the optical microscope for morphological research. The results showed that bacteria were more resistant than fungi to Cd2+, even cultured in high Cd2+ concentration up to 3000 mg·L-1,and it was 2000 mg·L-1 for fungi. Molecular identification of strains showed highest Cd2+ tolerance, then isolated and amplified the16 S r DNA and 18 S r DNA gene sequence. Results of bioinformatics analysis showed that isolated A1 strains may be the Sarocladium and A2 strains may be the Pseudomonas. This section enriched the information of bacteria and fungi species resistant to Cd2+, also provide a new research object for further research.This second parts studied the potential influence of several heavy metals on microbial biomass, activity, abundance, and community composition in arable soil near industrial estate in Zhuzhou, Hunan province, China. The results of Pearson correlation analysis showed that soil organic contents(SOC) were significantly positive correlated with heavy metals, whereas dehydrogenase activity(DHA) was greatly depressed by the heavy metal stress. Negative correlation was found between heavy metals and basal soil respiration(BSR), and no correlation was found between heavy metals and microbial biomass content(MBC). The quantitative PCR(QPCR) and polymerase chain reaction-denaturing gradient gel electrophoresis(PCR-DGGE) analysis could suggest that heavy metal pollution ha s significantly decreased abundance of bacteria and fungi and also changed their community structure. The results could contribute to evaluate heavy metal pollution level in farming land. Results of manually choosing RDA analysis indicated that the SOC, Cr and Cd were associated with a significant change of soil bacteria communities( p<0.005), respectively explained 26.9%(p=0.002), 6.8%(p=0.002) and 7.9%(p=0.005) of the soil bacterial community composition;Cr, SOC and Cu were significantly correlated with soil fungi community(p< 0.005), respectively explained 16.9%(p=0.002), 15.3%(p=0.002) and 9%(p=0.005) of the soil fungi community composition. By combining different environmental parameters, it would promote the better understanding of heavy metal effect on the abundance, structure, and activity of microbial community in arable soil. |
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