Fluctuation in recoverable nickel and zinc resistant copiotrophic bacteria explained by the varying zinc ion content of Torsa River in different months |
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Authors: | Bhaskar Bhadra Ashis Kumar Nanda Ranadhir Chakraborty |
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Institution: | (1) Department of Biotechnology, North Bengal University, Siliguri, 734430, West Bengal, India;(2) Department of Chemistry, North Bengal University, Siliguri, 734430, West Bengal, India;(3) Present address: Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500007, Andhra Pradesh, India |
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Abstract: | Heavy metal content analysis of River Torsa in India did not indicate any alarming level of toxicity for human consumption
but revealed variation at the ppb level in different months. The variation in recoverable nickel and zinc resistant copiotrophic
(or eutrophic) bacterial counts was explained by the variation of the zinc content (34.0–691.3 ppb) of the river water in
different sampling months. Growth studies conducted with some purified nickel and/or zinc resistant strains revealed that
pre-exposure of the cells to ppb levels of Zn2+, comparable to the indigenous zinc ion concentration of the river, could induce the nickel or zinc resistance. A minimum
concentration of 5–10 μM Zn2+ (325–650 ppb) was found effective in inducing the Nickel resistance of the isolates. Zinc resistance of the isolates was tested
by pre-exposing the cells to 4 μM Zn2+ (260 ppb). The lag phase was reduced by 6–8 h in all the cases. Biochemical characteristics and phylogenetic analysis based
on 16S rDNA sequence indicated that some of the Torsa River isolates, having inducible nickel and zinc resistance, are members
of the genus Pseudomonas, Acinetobacter, Bacillus, Enterobacter, Serratia and Moraxella. |
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Keywords: | Inducible metal resistance Torsa River Ni resistance Zn resistance River water bacteria |
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