Isolation And Identification Of Arsenic-Oxidizing Bacteria In Soil, And Oxidation Characteristics Research

Arsenic is a toxic metalloid element, resulting in environmental health problem. Arsenic mainly comes from geothermal movement, mining and human activities associated with arsenic. China is a large country of rice production and consumption, and rice is the main crop in south of China. In recent years arsenic pollution is increasingly serious in paddy soil, causing more attention. Arsenic in paddy soil is mainly composed of inorganic arsenite. As is known to all, the toxicity of arsenite is much higher than arsenate, as well as migration. So the toxicity and bioavailability will be greatly decreased when arsenite-oxidating occurs.This research aimed at separating, screening arsenite-oxidizing strains which can transform arsenite to arsenate, and studied about the characteristics of the oxidizing bacterial under various environmental conditions, in order to provide the basis for the repair of arsenic pollution.Using chemical defined media added arsenite, four oxidation bacteria strains were isolated from the polluted soil, respectively named Cl, AO-2, SY and Q54. Through the physiological and biochemical identification and phylogenetic analysis, four bacterial strains belonged to four different families. Strain Cl was identified as Shinella sp.,strain AO-2 as Pseudomonas sp., strain SY as Paracoccus sp., and strain Q54 as Rhizobium sp. At the same time, we explored the the influence of different environmental factors on the growth.To make use of the arsenite-oxidizing strains in the environmental remediation, we studied of the optimum growth conditions of strain SY. The study found that the optimum temperature of growth was 30℃; The optimal pH was 7.6.In order to explore strain SY in paddy soil where is no indigenous bacteria competition and no additional nutrients also can transform arsenite to arsenate, we carried out slurry experiment. Results showed that in the absence of indigenous bacteria competition, the strain SY will transform most of arsenite to arsenate.In addition, soil slurries experiment was also done, and explored the influence on rice of uptaking arsenic with arsenite-oxidizing strain SY. In paddy soil, the strain SY failed to colonize in the rhizosphere of rice, so it had no effect on arsenite uptake.