The Effect Of Heavy Metal Cr⁶⁺ On Hot Pepper Growth And Rhizosphere Soil Microbial Communities

Soil heavy metal pollution is becoming more and more serious. Heavy metals through the absorption of crop roots into the crop, after accumulation to a certain extent will produce harm to crops. And they may through the enrichment of the food chain into the people and animals, endangering human and animal health. Therefore, micro ecological risk assessment of heavy metal pollution samples, thus set up a corresponding system of risk assessment is an important task; At the same time, the screening of the fine repair strains of heavy metals, provide support to establish a method of microbial remediation of heavy metal pollution is also very critical.This research mainly did two aspects:on one hand, comprehensively investigated heavy metal pollution on soil microbial communities, and preliminary research about the mutual influence among heavy metals, microorganism and the plants growth; On the other hand, screened resistant strains from the heavy metal contaminated soil, to research their tolerance and repair ability, then to provide some support for the bioremediation of heavy metal pollution.The experiment used indoor pot experiment, adding different concentrations of Cr⁶⁺to the soil, transplanting into the hot pepper plants, regularly collecting soil samples and recording hot pepper growth, measuring the soil pH value and soil culturable bacteria quantity. Reveals the correlation of heavy metal Cr⁶⁺and pepper growth:appropriate concentration of Cr⁶⁺will accelerate the growth of pepper, as the concentration increases to inhibit the action of the growth gradually obvious, reaching a certain concentration can’t grow, for study the influence of heavy metal on crops in agricultural system provides the foundation; The addition of Cr⁶⁺had little influence on soil pH; And with the increase of concentration of Cr⁶⁺ in soil, the number of culturable bacteria is gradually reduced, and soil’s ability to repair itself is waning, shows the damage effect on soil environment, and the destruction of soil properties.Using terminal restriction fragment length polymorphism analysis （T-RFLP） and 454 pyrophosphate sequencing technology, to analysis the soil bacterial community with heavy metal pollution, the results show that the heavy metal Cr⁶⁺changed the bacterial diversity and community structure in soil. There is a close relationship between this effect and the concentration of Cr⁶⁺, at low concentrations （less than 0.20g/kg dry weight）, soil bacterial diversity and community structure changed slightly and duration of about 20 days; In high concentrations （0.50g/kg and 1.0 g/kg dry weight）, the soil bacterial diversity and community structure changed drastically, duration of about 50 days after began to recover, but the recovery ability is very weak. we found the influence of heavy metal Cr⁶⁺on capsicum rhizosphere soil microbes, takes a role in promoting the quantity of Actinobacteria, Streptomyces, Nocardioides species, but an inhibitory effect on Bacillus and most of the disadvantaged bacterium, destroys soil structure, makes many functional bacterias decrease. It reveals the importance of creating heavy metal pollution early warning system, provides guidance for agricultural production.From the soil contaminated with the high concentration of heavy metal Cr⁶⁺, we screened 9 strains of bacteria in the soil, resistance of bacterial J3, J5, J8 up to 2 mM, this three strains were selected as strong resistance strains, and to examine the repair capacity of Cr⁶⁺in corresponding liquid medium, they reached 17%,36% and 23%, respectively; It shows that they have good potential practical value, supply support for the repair of Cr⁶⁺pollution. For this strong resistance strains, the resistance mechanism, repair mechanisms, application in the actual production in the future or not and the ecological risk assessment are subject to further research.