Isolation, Identification And Functional Studies Of Arsenic-resisting Bacteria From Mine Tailing Dumps And Sediments Of SHIMEN In Hunan Province

With the development of society and economy,the human beings are facing a lot of problems. Arsenic pollution is becoming one of them. Bacteria play an important role in arsenic biogeochemistry, involving in biological reduction/oxidation, methylation/demethylation, precipitation/dissolution, and sorption/desorption. In consequence, different detoxifications strategies are developed to withstand the growth restriction when they expose to arsenic. So the study of arsenic resistant bacteria can provide a new way to solve the problem.13 arsenic resistant bacteria strains were enriched with 10×10-3mol/LNaAsO2 and isolated on plates from the samples from mine tailing dumps and sediments of SHIMEN in Hunan Province. All of them could not grow under anaerobic condition and were rod-shaped, Gram-negative. The 16S rRNA gene sequences were amplified from total DNA of bacteria strains, then sequenced and analyzed by MEGA 5.0. The phylogenetic tree analysis with 16S rRNA gene sequences of isolated bacteria strains was carried out. Results showed that all of isolated bacteria strains were belong to Pseudomonas otitidis and Pseudomonas aeruginosa.13 strains were all have a high resistance to arsenic(Ⅲ) and arsenate(Ⅴ), and strain SM-T1 was respectively resistant to the most arsenic(Ⅲ) of 60mmol/L and the most arsenate(Ⅴ) of 100mmol/L.Most strains were found could reduce arsenate after using KMnO4 method to identify arsenite oxidation or arsenate reduction. They used organism and dydrogen as electron acceptors for growth. Then the arsenic would oxidated by O2 or the strains which could oxidate arsenite. Arsenic specific resistant mechanisms were determined by identifying the six fuctional arsR, arsB, arsC, arrA, aoxA and aoxB genes based on PCR, only arsC was amplified from total DNA of strain SM-T1.The characteistics of strain SM-T1 was studied.It was found that SM-Tlcould reduce arsenate.Cells were single, non-spore forming,rod-shaped, Gram-negative, bacterial size (lengthxwidth):1 μm×0.5μm. Strain SM-T1 could not grow under the anaerobic condition.The pH range for growth was pH 5.0-9.0,with optimum growth at pH 7.0-8.0. The temperature range for growth was 15℃-35℃, with optimum growth at temperature 20℃. The arsenic of the concentration which was not enough to kill the cells could made an expressure on the bacteria’s growth rate,but less affected on the bacteria’s growth conditions. Phylogenetic analysis based on the 16S rRNA gene sequence showed that Pseudomonas aeruginosa PAO1(100% similar) was its closest relatives. Pseudomonas aeruginosa PAO1 have been found to reduce arsenate.