University School of Environment Management, Guru Gobind Singh Indraprsatha University, Sector 16-C, Dwarka, New Delhi, 110078, India.
Environ Monit Assess. 2018 Oct 26;190(11):674. doi: 10.1007/s10661-018-7061-0.
The occurrence of resistant bacteria to specific heavy metals can be associated with increasing load of the metals in the environment. River Yamuna is polluted by various toxic heavy metals discharged by several industrial and agricultural sources. Therefore, the use of heavy metal-resistant bacteria as an indicator of metal pollution was tested in the present study. For the purpose of the study, the heavy metal resistance status of 42 Escherichia coli strains isolated from River Yamuna water from 7 sampling sites within a span of 2 years was determined using growth curves and plate dilution method in terms of minimum inhibitory concentration (MIC) values by comparing with MIC value of control strain. Seasonally, the lowest mean MIC value was observed for bacterial strains isolated in post-monsoon (December) 2013 and highest mean MIC value was observed for bacterial strains isolated in monsoon (August) 2015. Site-wise analysis of the maximum mean MIC values for all the isolated strains showed the highest mean Ni MIC value for the bacterial strains isolated from site S4 (ITO), highest mean Cu MIC, Cr MIC, and Fe MIC values for the bacterial strains isolated from site S2 (Najafgarh drain intermixing zone) and highest mean Cd MIC, Pb MIC, and Zn MIC values for the bacterial strains isolated from site S7 (Shahdara drain intermixing zone). Correlation analysis between mean MIC site-wise results with mean heavy metal site-wise concentrations showed significant positive correlation indicating that the higher the mean concentration of a given heavy metal at a given site, the higher the mean MIC value for the strains isolated from the same site indicating higher level of resistance. Overall, the present study has shown that the presence of heavy metals in River Yamuna caused due to indiscriminate discharge of various effluents from different kind of sources as well as due to insufficient treatment capacity of sewage treatment plants as well as common effluent treatment plants, has serious impacts on its bacterial microflora as it leads to the development of resistant strains.
河流亚穆纳受到各种工业和农业污染源排放的有毒重金属的污染。因此，本研究测试了耐重金属细菌作为金属污染指标的使用。
为了进行这项研究，使用生长曲线和平板稀释法，通过与对照菌株的最小抑菌浓度 (MIC) 值进行比较，确定了从亚穆纳河水中分离出的 42 株大肠杆菌菌株在 2 年内 7 个采样点的重金属抗性状况。按季节来看，2013 年季风后（12 月）分离的细菌菌株的平均 MIC 值最低，而 2015 年季风期（8 月）分离的细菌菌株的平均 MIC 值最高。对所有分离菌株的最大平均 MIC 值进行站点分析，结果表明，从 S4 点（ITO）分离的细菌菌株的平均 Ni MIC 值最高，从 S2 点（纳杰夫加尔污水混合区）分离的细菌菌株的平均 Cu MIC、Cr MIC 和 Fe MIC 值最高，从 S7 点（沙哈达污水混合区）分离的细菌菌株的平均 Cd MIC、Pb MIC 和 Zn MIC 值最高。
站点平均 MIC 值与站点平均重金属浓度之间的相关分析显示，存在显著的正相关关系，这表明在给定地点，给定重金属的平均浓度越高，从同一地点分离出的菌株的平均 MIC 值越高，这表明其抗性水平更高。
总体而言，本研究表明，由于各种来源的污水未经区分地排放，以及污水处理厂和综合污水厂的处理能力不足，导致亚穆纳河中的重金属含量过高，这对其细菌微生物群造成了严重影响，导致了抗性菌株的产生。
