Macur Richard E, Jackson Colin R, Botero Lina M, McDermott Timothy R, Inskeep William P
Department of Land Resources and Environmental Sciences, Montana State University-Bozeman, Bozeman, Montana 59717, USA.
Environ Sci Technol. 2004 Jan 1;38(1):104-11. doi: 10.1021/es034455a.
Microbial populations responsible for the oxidation and reduction of As were examined in unsaturated (aerobic) soil columns treated with 75 microM arsenite [As(III)] or 250 microM arsenate [As(V)]. Arsenite [As(III)] was rapidly oxidized to As(V) via microbial activity, whereas no apparent reduction of As(V) was observed in the column experiments. Eight aerobic heterotrophic bacteria with varying As redox phenotypes were isolated from the same columns. Three isolates, identified as Agrobacterium tumefaciens-, Pseudomonas fluorescens-, and Variovorax paradoxus-like organisms (based on 16S sequence), were As(III) oxidizers, and all were detected in community DNA fingerprints generated by PCR coupled with denaturing gradient gel electrophoresis. The five other isolates were identified (16S gene sequence) as A. tumefaciens, Flavobacterium sp., Microbacterium sp., and two Arthrobacter sp. -like organisms and were shown to rapidly reduce As(V) under aerobic conditions. Although the two A. tumefaciens-like isolates exhibited opposite As redox activity,their 16S rDNA sequences (approximately 1400 bp) were 100% identical, and both were shown to contain putative arsC genes. Our results support the hypothesis that bacteria capable of either oxidizing As(III) or reducing As(V) coexist and are ubiquitous in soil environments, suggesting that the relative abundance and metabolic activity of specific microbial populations plays an important role in the speciation of inorganic As in soil pore waters.
在分别用75微摩尔亚砷酸盐[As(III)]或250微摩尔砷酸盐[As(V)]处理的非饱和（好氧）土壤柱中，研究了负责砷氧化和还原的微生物群落。通过微生物活动，亚砷酸盐[As(III)]迅速氧化为As(V)，而在柱实验中未观察到As(V)有明显还原。从同一土壤柱中分离出8种具有不同砷氧化还原表型的好氧异养细菌。3种分离菌（基于16S序列鉴定为根癌土壤杆菌、荧光假单胞菌和奇异贪铜菌样微生物）是As(III)氧化菌，并且在通过聚合酶链反应（PCR）结合变性梯度凝胶电泳产生的群落DNA指纹图谱中均检测到。另外5种分离菌（16S基因序列）鉴定为根癌土壤杆菌、黄杆菌属、微杆菌属以及两种节杆菌属样微生物，并且显示在好氧条件下能迅速还原As(V)。尽管两种根癌土壤杆菌样分离菌表现出相反的砷氧化还原活性，但其16S rDNA序列（约1400 bp）100%相同，并且均显示含有假定的arsC基因。我们的结果支持以下假设：能够氧化As(III)或还原As(V)的细菌共存且在土壤环境中普遍存在，这表明特定微生物群落的相对丰度和代谢活性在土壤孔隙水中无机砷的形态形成中起重要作用。
