Cavalca Lucia, Zecchin Sarah, Zaccheo Patrizia, Abbas Ben, Rotiroti Marco, Bonomi Tullia, Muyzer Gerard
Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente (DeFENS), Università degli Studi di Milano, Milan, Italy.
Dipartimento di Scienze Agrarie e Ambientali - Produzione, Territorio, Agroenergia (DiSAA), Università degli Studi di Milano, Milan, Italy.
Front Microbiol. 2019 Jul 2;10:1480. doi: 10.3389/fmicb.2019.01480. eCollection 2019.
Arsenic contamination of groundwater aquifers is an issue of global concern. Among the affected sites, in several Italian groundwater aquifers arsenic levels above the WHO limits for drinking water are present, with consequent issues of public concern. In this study, for the first time, the role of microbial communities in metalloid cycling in groundwater samples from Northern Italy lying on Pleistocene sediments deriving from Alps mountains has been investigated combining environmental genomics and cultivation approaches. 16S rRNA gene libraries revealed a high number of yet uncultured species, which in some of the study sites accounted for more of the 50% of the total community. Sequences related to arsenic-resistant bacteria (arsenate-reducing and arsenite-oxidizing) were abundant in most of the sites, while arsenate-respiring bacteria were negligible. In some of the sites, sulfur-oxidizing bacteria of the genus accounted for more than 50% of the microbial community, whereas iron-cycling bacteria were less represented. In some aquifers, arsenotrophy, growth coupled to autotrophic arsenite oxidation, was suggested by detection of arsenite monooxygenase () and 1,5-ribulose bisphosphate carboxylase (RuBisCO) genes of microorganisms belonging to and . Enrichment cultures established from sampled groundwaters in laboratory conditions with 1.5 mmol L of arsenite as sole electron donor were able to oxidize up to 100% of arsenite, suggesting that this metabolism is active in groundwaters. The presence of heterotrophic arsenic resistant bacteria was confirmed by enrichment cultures in most of the sites. The overall results provided a first overview of the microorganisms inhabiting arsenic-contaminated aquifers in Northern Italy and suggested the importance of sulfur-cycling bacteria in the biogeochemistry of arsenic in these ecosystems. The presence of active arsenite-oxidizing bacteria indicates that biological oxidation of arsenite, in combination with arsenate-adsorbing materials, could be employed for metalloid removal.
地下含水层的砷污染是一个全球关注的问题。在受影响的地区中，意大利的几个地下含水层中存在高于世界卫生组织饮用水标准的砷含量，引发了公众关注的问题。在本研究中，首次结合环境基因组学和培养方法，对源自阿尔卑斯山更新世沉积物的意大利北部地下水样本中微生物群落参与类金属循环的作用进行了研究。16S rRNA基因文库揭示了大量尚未培养的物种，在一些研究地点，这些物种占群落总数的50%以上。与抗砷细菌（砷酸盐还原菌和亚砷酸盐氧化菌）相关的序列在大多数地点都很丰富，而砷酸盐呼吸细菌则可忽略不计。在一些地点，硫氧化细菌属占微生物群落的50%以上，而铁循环细菌的占比则较小。在一些含水层中，通过检测属于 和 的微生物的亚砷酸盐单加氧酶（）和1,5-二磷酸核酮糖羧化酶（RuBisCO）基因，表明存在以自养亚砷酸盐氧化为耦合的砷营养生长。在实验室条件下，以1.5 mmol/L亚砷酸盐作为唯一电子供体，从采集的地下水中建立的富集培养物能够将高达100%的亚砷酸盐氧化，这表明这种代谢在地下水中具有活性。大多数地点的富集培养证实了异养抗砷细菌的存在。总体结果首次概述了意大利北部受砷污染含水层中的微生物，并表明硫循环细菌在这些生态系统中砷的生物地球化学中的重要性。活性亚砷酸盐氧化细菌的存在表明，亚砷酸盐的生物氧化与砷酸盐吸附材料相结合，可用于去除类金属。
