INAIL-Research, Certification, Verification Area, Department of Productive Plants and Human Settlements (DIPIA), Via Urbana, 167, 00184 Rome, Italy.
Ecotoxicol Environ Saf. 2013 Oct;96:1-9. doi: 10.1016/j.ecoenv.2013.05.039. Epub 2013 Jul 17.
Latium, a region in central Italy, is known for its extensive volcanic areas that make a significant contribution to the arsenic (As) contamination of freshwater environments, even though some degree of As water pollution may be caused by human activities. The information available on indigenous As-resistant prokaryotes in aquatic environments of Latium is, however, still limited. In this study, we describe new bacteria that are resistant to arsenic toxicity and were isolated from the surface waters of Lake Vico and the Sacco River, two groundwater systems in Latium, as well as from bottled natural mineral water from the same region. The 16S rRNA gene sequence analysis for the As-resistant strains in lake and river waters points to a prevalence of β- and γ-Proteobacteria, while α-Proteobacteria, Firmicutes and Bacteroidetes are represented to a lesser extent. By contrast, solely γ-Proteobacteria were isolated from groundwater samples. The presence of Actinobacteria was documented exclusively in bottled mineral water. In addition, we conducted a DNA sequence-based study on the gene codifying arsB, an As(III) efflux membrane protein pump related to arsenic resistance, for all the As-resistant bacterial isolates. A phylogenetic analysis was carried out on the newly sequenced 16S rRNA genes and arsB in the present study as well as on an additional 16S rRNA/arsB dataset we obtained previously from Lake Albano, from the Tiber and from a well in Bassano Romano located in Latium (Davolos and Pietrangeli, 2011). Overall, the phylogenetic diversity of As-resistant bacteria in underground water was very limited if compared with lentic and lotic waters. Lastly, our molecular data support the hypothesis that the horizontal gene transfer of ars in As-containing freshwater environments is not limited to closely-related genomes, but also occurs between bacteria that are distant from an evolutionary viewpoint, thereby indicating that such genetic events may be considered a source of microbial resistance to arsenic-toxicity.
拉齐奥，意大利中部的一个地区，以其广泛的火山地区而闻名，这些地区对淡水环境中的砷（As）污染有重大贡献，尽管一定程度的砷水污染可能是由人类活动引起的。然而，关于拉齐奥水生环境中土著砷抗性原核生物的信息仍然有限。在这项研究中，我们描述了从拉齐奥的两个地下水系统——维科湖和萨科河的地表水以及同一地区的瓶装天然矿泉水分离出的抗砷毒性的新细菌。对来自湖泊和河流的砷抗性菌株的 16S rRNA 基因序列分析表明，β-和γ-变形菌占优势，而α-变形菌、厚壁菌门和拟杆菌门则相对较少。相比之下，仅从地下水样本中分离出γ-变形菌。放线菌的存在仅在瓶装矿泉水中有记录。此外，我们对所有抗砷细菌分离株的编码砷（III）外排膜蛋白泵 arsB 的基因进行了基于 DNA 序列的研究。对本研究中新测序的 16S rRNA 基因和 arsB 以及我们之前从拉齐奥的阿尔巴诺湖、台伯河和巴索罗马诺的一口井获得的 16S rRNA/arsB 数据集进行了系统发育分析（Davolos 和 Pietrangeli，2011）。总体而言，如果将地下水与静水和流水进行比较，那么抗砷细菌的系统发育多样性非常有限。最后，我们的分子数据支持这样的假设，即在含砷淡水环境中，ars 的水平基因转移不仅限于密切相关的基因组，而且还发生在从进化角度来看距离较远的细菌之间，这表明此类遗传事件可被视为微生物对砷毒性抗性的来源。
