Instituto Amazónico de Investigaciones Científicas SINCHI, 110321, Bogotá, Colombia.
Faculty of Engineering, Universidad de La Sabana, Chía, Colombia.
Appl Microbiol Biotechnol. 2022 Apr;106(7):2775-2793. doi: 10.1007/s00253-022-11860-y. Epub 2022 Mar 28.
Two sites of the Colombian Amazon region with different levels of human intervention and mercury pollution were selected for the collection of samples of river and lake water, sediments, and associated forest soils. The Tarapacá region, affected mainly by barrage mining, showed low mercury concentrations, whilst in the Taraira region, affected by underground mining, there were several points with high mercury pollution levels. A collection of 72 bacterial and 10 yeast strains with different levels of mercury resistance was isolated and characterized. Most of the highly resistant bacterial strains (MIC > 40 mg L HgCl) were isolated from soil and sediment samples and belonged to either Pseudomonas (60%) or Bacillus (20%). Most of highly resistant bacterial strains were positive for the presence of the merA gene, suggesting an active mercury resistance mechanism. This was confirmed in the two most resistant strains, Pseudomonas sp. TP30 and Burkholderia contaminans TR100 (MIC = 64 and 71 mg L HgCl, respectively), which in the presence of increasing mercury concentrations expressed the merA gene at increasing levels, concomitant with a significant mercury reduction activity. Analysis of the MerA sequences present in the different isolates suggested a high gene conservation within the taxonomic groups but also several horizontal gene transfer events between taxonomically distant genera. We also observed a positive correspondence between the presence of the merA gene and the number of antibiotics to which the strains were resistant to. The most resistant strains are good candidates for future applications in the bioremediation of mercury-contaminated sites in the Amazon.Key points• Amazon sediments affected by underground gold mining have higher Hg levels.• Highly Hg-resistant isolates belonged to Pseudomonas and Bacillus genera.• TR100 and TP30 strains showed remediation potential to be used in the Amazon region.
选择了哥伦比亚亚马逊地区的两个具有不同人为干预和汞污染水平的地点，以采集河水、湖水、沉积物和相关森林土壤样本。受拦河坝开采影响的塔拉帕卡地区汞浓度较低，而受地下开采影响的塔拉雷拉地区则有几个点汞污染水平较高。收集了 72 株具有不同汞抗性水平的细菌和 10 株酵母菌株，并对其进行了分离和鉴定。大多数高度抗汞的细菌菌株（MIC＞40mgLHgCl）是从土壤和沉积物样本中分离出来的，属于假单胞菌（60%）或芽孢杆菌（20%）。大多数高度抗汞的细菌菌株都存在 merA 基因，表明存在一种活跃的汞抗性机制。在两个最抗汞的菌株中得到了证实，即假单胞菌 sp. TP30 和伯克霍尔德菌 contaminans TR100（MIC=64 和 71mgLHgCl），在汞浓度不断增加的情况下，merA 基因表达水平不断提高，同时具有显著的汞还原活性。对不同分离株中存在的 MerA 序列的分析表明，在分类群内基因高度保守，但在分类上相距较远的属之间也发生了几次水平基因转移。我们还观察到 merA 基因的存在与菌株对多种抗生素的抗性之间存在正相关性。最抗汞的菌株是未来在亚马逊地区受汞污染场地进行生物修复的良好候选者。
