Isolation and Characterization of arsenite-oxidizing bacteria Bosea sp. str. L7506 from Arsenic-contaminated Groundwater in Blackfoot Disease Region in Taiwan
Date Issued
2007
Date
2007
Author(s)
Hsu, Hsiang-Yen
DOI
en-US
Abstract
Arsenic is an environmental carcinogen of toxicological concern. Although arsenic is generally toxic to life, it has been demonstrated that some microorganisms can use arsenic compounds as electron donors, electron acceptors, or possess arsenic detoxification mechanisms. Increasing evidences suggest that the biogeochemical cycle of arsenic is significantly dependent on microbial transformations which affect the distribution and the mobility of arsenic species in the environment. However, the roles of the bacteria in the arsenic cycles are yet to be fully elucidated. In this study, we isolate arsenite-arsenate redox bacteria using known arsenic-contaminated groundwater in Blackfoot disease region in Taiwan under oxic condition. Three hundred and forty-five arsenic-resistant bacterial strains were isolated. A microplate color screening assay with addition of AgNO3 was used to initially characterize the ability of oxidation and reduction of those bacteria. Eighty-seven bacteria were capable of arsenate reduction, whereas only one bacterial strain L7506 was characterized as arsenite oxidizer. Analysis of the 16S rRNA gene sequence of the isolated bacteria revealed that some of the bacteria have been indicated involving in arsenic transformation, while others have not been reported to be associated with arsenic transformation. The designated strain L7506 was selected for further investigation. It is a Gram-negative, straight to curved rod, and motile bacteria. It belongs to genus Bosea based on 16S rRNA sequence analysis. The optimal growth condition was at pH 7.4-8.4, 37℃ in LB medium. Moreover, it was able to grow in the presence of 100mM arsenate. Substrate test showed that Bosea sp. str. L7506 is an autotrophic bacterium. However, the addition of appropriate substrate and carbon sources enhance its growth rate even in the presence of 2mM arsenite. Arsenite transformation analysis showed that Bosea sp. str. L7506 completely oxidized 2mM (150ppm) of arsenite to arsenate within 3 days without the presence of any nutrient, and within 2 days when cultured in groundwater samples. Furthermore, the large subunit of the arsenite oxidase gene was cloned using a pair of degenerate primers. Arsenite oxidase activity was stimulated by 2mM arsenite and was present in both periplasm and spheroplast of the bacteria. Taken together, results from this study showed that diverse bacteria were present in arsenic-contaminated groundwater in Blackfoot disease region in Taiwan. The identified arsenite-oxidizing bacteria may be potentially used for bioremediation of arsenic-contaminated groundwater.
Subjects
砷
微生物
地下水
三價砷氧化菌
Bosea. sp. str. L7506
復育
arsenite-oxidation
groundwater
bioremediation
bacteria
SDGs
Type
thesis