Gene Expression Laboratory, Department of Biosciences, Jamia Millia Islamia, New Delhi.
Can J Microbiol. 2011 Oct;57(10):769-74. doi: 10.1139/w11-062. Epub 2011 Sep 21.
Contamination of the environment with heavy metals has increased drastically over the last few decades. The heavy metals that are toxic include mercury, cadmium, arsenic, and selenium. Of these heavy metals, arsenic is one of the most important global environmental pollutants and is a persistent bioaccumulative carcinogen. It is a toxic metalloid that exists in two major inorganic forms: arsenate and arsenite. Arsenite disrupts enzymatic functions in cells, while arsenate behaves as a phosphate analog and interferes with phosphate uptake and utilization. Despite its toxicity, arsenic may be actively sequestered in plant and animal tissues. Various microbes interact with this metal and have shown resistance to arsenic exposure, and they appear to possess the ars operon for arsenic resistance consisting of three to five genes, i.e., arsRBC or arsRDABC, organized into a single transcriptional unit; some microbes even use it for respiration. Microbial interactions with metals may have several implications for the environment. Microbes may play a role in cycling of toxic heavy metals and in remediation of metal-contaminated sites. There is a correlation between tolerance to heavy metals and antibiotic resistance, a global problem currently threatening the treatment of infections in plants, animals, and humans. The purpose of this review is to highlight the nature and role of toxic arsenic in bacterial systems and to discuss the various genes responsible for this heavy-metal resistance in nature and the mechanisms to detoxify this element.
在过去几十年中，环境中的重金属污染急剧增加。有毒重金属包括汞、镉、砷和硒。在这些重金属中，砷是最重要的全球环境污染物之一，也是一种持久的生物累积性致癌物。它是一种有毒的类金属，存在两种主要的无机形式：砷酸盐和亚砷酸盐。亚砷酸盐会破坏细胞中的酶功能，而砷酸盐则表现为磷酸盐类似物，干扰磷酸盐的摄取和利用。尽管砷具有毒性，但它可能会在植物和动物组织中被主动隔离。各种微生物与这种金属相互作用，表现出对砷暴露的抗性，并且它们似乎拥有用于砷抗性的 ars 操纵子，由三个到五个基因组成，即 arsRBC 或 arsRDABC，组织成单个转录单元；有些微生物甚至将其用于呼吸。微生物与金属的相互作用可能对环境有多种影响。微生物可能在有毒重金属的循环和受金属污染的地点的修复中发挥作用。重金属耐受性与抗生素耐药性之间存在相关性，这是目前全球范围内威胁植物、动物和人类感染治疗的一个问题。本文综述的目的是强调有毒砷在细菌系统中的性质和作用，并讨论负责这种重金属抗性的各种基因以及解毒这种元素的机制。
