Mercury-tolerant metalophiles: A bio tool for remediation of mercury (Hg) affected Environs

Abstract

Due to their low solubility, carcinogenic and mutagenic effects, heavy metals are of critical concern to humans and the environment. Mercury (Hg) is one of the rarest and least concentrated elements in the world, but it is ranked third in terms of toxicity. The present investigation evaluates the response and tolerance limit of bacteria isolated from the saffron soil of the Kashmir Valley to various mercury concentrations (50 ppm to 400 ppm). The minimum inhibitory concentration (MIC) was calculated after 24hours by measuring the optical density. Isolated bacteria have been characterized using two efficient methods, i.e. 16S rRNA gene sequence and MALDI-TOF MS. A total of 72 isolates were investigated for the mercury tolerance and among them, only 8 isolates (Staphylococcus equorum, Leclercia adecarboxylata, Staphylococcus warneri, Klebsiella pneumoniae, Serratia plymuthica, Bacillus megaterium, Pseudomonas putida and Bacillus safensis) were found tolerant to mercury with varying MIC. In comparison, Pseudomonas putida has been found to have the maximum resistance (400 ppm) for mercury and S. plymuthica and L. adecarboxylate had the lowest resistance level (200 ppm). The sequestration potential results revealed that P. putida executed the highest sequestration potential (73%) while K. pneumoniae showed the lowest sequestration potential (51.63%). Thus mercury tolerance capacity of these species may be utilised for detoxification and removal of mercury from polluted sites, providing an eco-friendly technique for bioremediation of mercury-affected environments.