Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA.
Biodegradation. 2012 Feb;23(1):133-43. doi: 10.1007/s10532-011-9493-x. Epub 2011 Jun 26.
Arsenic is a carcinogenic compound widely distributed in the groundwater around the world. The fate of arsenic in groundwater depends on the activity of microorganisms either by oxidizing arsenite (As(III)), or by reducing arsenate (As(V)). Because of the higher toxicity and mobility of As(III) compared to As(V), microbial-catalyzed oxidation of As(III) to As(V) can lower the environmental impact of arsenic. Although aerobic As(III)-oxidizing bacteria are well known, anoxic oxidation of As(III) with nitrate as electron acceptor has also been shown to occur. In this study, three As(III)-oxidizing bacterial strains, Azoarcus sp. strain EC1-pb1, Azoarcus sp. strain EC3-pb1 and Diaphorobacter sp. strain MC-pb1, have been characterized. Each strain was tested for its ability to oxidize As(III) with four different electron acceptors, nitrate, nitrite, chlorate and oxygen. Complete As(III) oxidation was achieved with both nitrate and oxygen, demonstrating the novel ability of these bacterial strains to oxidize As(III) in either anoxic or aerobic conditions. Nitrate was only reduced to nitrite. Different electron donors were used to study their suitability in supporting nitrate reduction. Hydrogen and acetate were readily utilized by all the cultures. The flexibility of these As(III)-oxidizing bacteria to use oxygen and nitrate to oxidize As(III) as well as organic and inorganic substrates as alternative electron donors explains their presence in non-arsenic-contaminated environments. The findings suggest that at least some As(III)-oxidizing bacteria are flexible with respect to electron-acceptors and electron-donors and that they are potentially widespread in low arsenic concentration environments.
砷是一种广泛分布于世界各地地下水的致癌化合物。砷在地下水中的命运取决于微生物的活性，这些微生物可以通过氧化亚砷酸盐（As(III)），或通过还原砷酸盐（As(V)）来实现。由于与 As(V)相比，As(III)的毒性和迁移性更高，因此微生物催化的 As(III)氧化为 As(V)可以降低砷的环境影响。尽管好氧的 As(III)氧化细菌是众所周知的，但也已经证明了缺氧条件下，硝酸盐作为电子受体的 As(III)氧化也会发生。在本研究中，我们对三株 As(III)氧化细菌菌株，Azoarcus sp. strain EC1-pb1、Azoarcus sp. strain EC3-pb1 和 Diaphorobacter sp. strain MC-pb1 进行了表征。每株菌株都被测试了其使用四种不同的电子受体（硝酸盐、亚硝酸盐、氯酸盐和氧气）氧化 As(III)的能力。硝酸盐和氧气都可以完全氧化 As(III)，这证明了这些细菌菌株在缺氧或好氧条件下氧化 As(III)的新颖能力。硝酸盐仅被还原为亚硝酸盐。不同的电子供体被用于研究它们在支持硝酸盐还原中的适用性。氢气和乙酸盐被所有培养物都容易地利用。这些 As(III)氧化细菌使用氧气和硝酸盐氧化 As(III)以及有机和无机底物作为替代电子供体的灵活性，解释了它们在非砷污染环境中的存在。这些发现表明，至少一些 As(III)氧化细菌在电子受体和电子供体方面具有灵活性，并且它们在低砷浓度环境中可能广泛存在。
