Anderson Craig R, Cook Gregory M
Department of Microbiology, Otago School of Medical Sciences, University of Otago, P.O. Box 56, Dunedin, New Zealand.
Curr Microbiol. 2004 May;48(5):341-7. doi: 10.1007/s00284-003-4205-3.
Two environmental sites in New Zealand were sampled (e.g., water and sediment) for bacterial isolates that could use either arsenite as an electron donor or arsenate as an electron acceptor under aerobic and anaerobic growth conditions, respectively. These two sites were subjected to widespread arsenic contamination from mine tailings generated from historic gold mining activities or from geothermal effluent. No bacteria were isolated from these sites that could utilize arsenite or arsenate under the respective growth conditions tested, but a number of chemoheterotrophic bacteria were isolated that could grow in the presence of high concentrations of arsenic species. In total, 17 morphologically distinct arsenic-resistant heterotrophic bacteria isolates were enriched from the sediment samples, and analysis of the 16S rRNA gene sequence of these bacteria revealed them to be members of the genera Exiguobacterium, Aeromonas, Bacillus, Pseudomonas, Escherichia, and Acinetobacter. Two isolates, Exiguobacterium sp. WK6 and Aeromonas sp. CA1, were of particular interest because they appeared to gain metabolic energy from arsenate under aerobic growth conditions, as demonstrated by an increase in cellular growth yield and growth rate in the presence of arsenate. Both bacteria were capable of reducing arsenate to arsenite via a non-respiratory mechanism. Strain WK6 was positive for arsB, but the pathway of arsenate reduction for isolate CA1 was via a hitherto unknown mechanism. These isolates were not gaining an energetic advantage from arsenate or arsenite utilization, but were instead detoxifying arsenate to arsenite. As a subsidiary process to arsenate reduction, the external pH of the growth medium increased (i.e., became more alkaline), allowing these bacteria to grow for extended periods of time.
在新西兰的两个环境地点（例如水和沉积物）进行了采样，以获取在有氧和厌氧生长条件下分别能够使用亚砷酸盐作为电子供体或砷酸盐作为电子受体的细菌分离株。这两个地点受到了历史悠久的金矿开采活动产生的尾矿或地热废水造成的广泛砷污染。在所测试的各自生长条件下，未从这些地点分离出能够利用亚砷酸盐或砷酸盐的细菌，但分离出了一些能够在高浓度砷物种存在的情况下生长的化学异养细菌。总共从沉积物样本中富集了17种形态上不同的抗砷异养细菌分离株，对这些细菌的16S rRNA基因序列分析表明它们属于微小杆菌属、气单胞菌属、芽孢杆菌属、假单胞菌属、大肠杆菌属和不动杆菌属。两个分离株特别令人感兴趣，即微小杆菌属WK6菌株和气单胞菌属CA1菌株，因为在有氧生长条件下，它们似乎从砷酸盐中获取代谢能量，这表现为在存在砷酸盐的情况下细胞生长产量和生长速率增加。两种细菌都能够通过非呼吸机制将砷酸盐还原为亚砷酸盐。WK6菌株的arsB呈阳性，但CA1分离株的砷酸盐还原途径是通过一种迄今未知的机制。这些分离株并非从利用砷酸盐或亚砷酸盐中获得能量优势，而是将砷酸盐解毒为亚砷酸盐。作为砷酸盐还原的一个附属过程，生长培养基的外部pH值升高（即变得更碱性），使这些细菌能够长时间生长。
