五價砷還原菌Citrobacter sp. strain L2之特性分析

Characterization of an arsenate-reducing bacterium Citrobacter sp. strain L2

林柏成(Po-Cheng Lin)

指導教授 ： 廖秀娟

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.10626

摘要

地下水受砷污染是一個全球性的公共衛生議題，全球各地超過數千萬人因為長期飲用含砷的地下水，因而產生健康上的危害。在1960年代，臺灣西南沿海地區的居民飲用了含砷的地下水，於是造成烏腳病以及其他癌症的生成。目前有越來越多證據顯示微生物在地下水中的砷釋出扮演了重要的角色，但是詳細的釋出機制與微生物之間交互作用並不是很瞭解。Strain L2是一隻從雲林地區含砷地下水所分離出來的五價砷還原菌，16S rDNA序列的分析顯示，strain L2屬於Citrobacter菌屬。本研究針對strain L2進行了電子提供者與接受者的測試，還有生長曲線與五價砷還原的探討。Strain L2能夠在兩天之內將200 μM (15 ppm)的五價砷還原。PCR的結果顯示strain L2含有arsC基因，此基因所轉譯的蛋白質是催化五價砷還原的功能。另外，利用跳躍子產生strain L2的突變株，進而篩選失去五價砷還原能力的菌株，探討是否含有其他未知的基因與五價砷還原有關。結果顯示mogA的突變會造成五價砷還原能力下降。MogA是molybdopterin biosynthesis protein，在molybdenum cofactor的生合成路徑當中扮演重要角色。有關mogA突變株的生理特性，砷還原能力，以及其生化功能會在本篇論文中探討。

關鍵字

砷 ； Citrobacter sp. strain L2 ； mogA

並列摘要

The contamination of arsenic in groundwater has caused a serious public health crisis. Over millions of people are exposing to arsenic by drinking arsenic contaminated well water, which occurred in the south-west part of Taiwan in 1960s, resulting in the Blackfoot disease and various cancers. Evidences have suggested that arsenic released from solid phase into aqueous phase is mediated by microbial interaction. However, the relationship of arsenic mobilization and microbial interaction in aquifer are poorly studied. Strain L2 is an arsenate-reducing bacterium isolated from arsenic contaminated groundwater. Analysis of 16S rDNA showed that it belongs to the genus of Citrobacter. In this study, the electron donor and acceptor tests, growth curve, and arsenate transformation of strain L2 was investigated. Strain L2 was able to reduce 200 μM (15 ppm) arsenate in less than 2 days. PCR amplification showed that strain L2 contained arsC gene, which encodes the cytoplasmic arsenate reductase. Moreover, transposon mutagenesis was performed to identify novel genes involved in arsenate reduction. Identification of arsenate reduction mutants showed that the disruption of mogA resulted in the decrease of arsenate reduction ability. MogA encodes the molybdopterin biosynthesis protein, which involves in the biosynthetic pathway of molybdenum cofactor formation. The physiological property and biochemical insights of mogA mutant with arsenate reduction were discussed.

並列關鍵字

arsenic ； Citrobacter sp. strain L2, ； mogA

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