Naguib Martha M, Khairalla Ahmed S, El-Gendy Ahmed O, Elkhatib Walid F
a Department of Biotechnology and Life Sciences, Faculty of Post Graduate Studies for Advanced Sciences, Beni-Suef University, Beni-Suef, Egypt.
b Department of Microbiology & Immunology, Faculty of Pharmacy, Beni-Suef University, Beni-Suef, Egypt.
Can J Microbiol. 2019 Apr;65(4):308-321. doi: 10.1139/cjm-2018-0379. Epub 2019 Jan 11.
An important mechanism for microbial resistance to mercury is its reduction into elemental mercury (facilitated by the merA gene). Thirty-eight microbial isolates from a variety of wastewater sources in Egypt were collected. Approximately 14 of the 38 isolates exhibited not only a high degree of tolerance to mercury (up to 160 ppm) but also a high degree of resistance to other tested heavy metals (Cu, Co, Ni, and Zn). From these 14, the 10 most resistant isolates were selected for further study and were found to include 9 Gram-negative and 1 Gram-positive bacterial strains. Multi-antibiotic-resistance profiles were detected for 6 out of the 10 selected isolates. All the tested Gram-negative isolates (n = 9) harbored a plasmid-encoded merA gene. The mercury removal effectiveness for the 10 selected isolates ranged between 50% and 99.9%, among which Stenotrophomonas maltophilia ADW10 recorded the highest rate (99.9%; at an initial mercury concentration of 20 ppm). To the best of our knowledge, this is the first study to (i) demonstrate the presence of a multimetal-resistant S. maltophilia bacterium with a high mercury tolerance capacity that would make it a suitable candidate for future bioremediation efforts in heavy-metal-polluted areas in Egypt and (ii) report Pseudomonas otitidis as one of the mercury-resistant bacteria.
微生物对汞产生抗性的一个重要机制是将其还原为元素汞（由merA基因促成）。从埃及各种废水源中收集了38株微生物分离株。38株分离株中约有14株不仅对汞具有高度耐受性（高达160 ppm），而且对其他受试重金属（铜、钴、镍和锌）也具有高度抗性。从这14株中，挑选出10株抗性最强的分离株进行进一步研究，发现其中包括9株革兰氏阴性菌和1株革兰氏阳性菌。在10株挑选出的分离株中，检测到6株具有多重抗生素抗性谱。所有受试革兰氏阴性分离株（n = 9）都含有质粒编码的merA基因。10株挑选出的分离株的汞去除效率在50%至99.9%之间，其中嗜麦芽窄食单胞菌ADW10的去除率最高（99.9%；初始汞浓度为20 ppm）。据我们所知，这是第一项（i）证明存在一种对多种金属具有抗性且对汞具有高耐受性的嗜麦芽窄食单胞菌，这使其成为埃及重金属污染地区未来生物修复工作的合适候选者，以及（ii）将耳炎假单胞菌报告为耐汞细菌之一的研究。
