Abstract
The nickel-resistant bacterium, Cupriavidus pauculus KPS 201 was isolated from the rhizosphere of Rinorea bengalensis (Wall.) O. K. endemic to metal-percolated ultramafic ecosystem of Andaman, India. This study investigates nature of Ni resistance, growth associated uptake and localization of Ni in cellular compartments of KPS 201. Growth kinetics of C. pauculus KPS 201 exhibited a typical inducible Ni resistance in Ni-supplemented (1.0-10.0 mM) Tris-minimal medium. The Ni-induced cells showed a high degree of Ni resistance and accumulated a maximum of 29.3 µM Ni/g protein after 48 h of growth in 5 mM Ni. The accumulated Ni was preferentially retained (90.6%) in the periplasm and was associated with the expression of two periplasmic proteins (74 and 66 kDa) under Ni-induced condition. Inducible nickel resistance in C. pauculus KPS 201 may possibly be due to extracytoplasmic binding and accumulation coupled with expression of specific periplasmic proteins. These findings will provide an insight in understanding metal-microbe interaction in geogenous environments and their exploitation in bioremediation of heavy metal pollutants.
Highlights
Ultramafic ecosystem comprises nutritionally poor, metal enriched soils characterized by high concentrations of nickel in addition to chromium and cobalt [1]
Our present study investigates the nature of Ni resistance, growth associated uptake and possible localization of accumulated Ni in C. pauculus KPS 201 cells
Similar induction of Ni resistance system in Burkholderia 32W-2, native to New Caledonian ultramafics was evident at 1.0 mM Ni [3]
Summary
Ultramafic ecosystem comprises nutritionally poor, metal enriched soils characterized by high concentrations of nickel in addition to chromium and cobalt [1]. Majority of the endemic metallophytes inhabiting such ecosystem are Ni-hyperaccumulators which provide a niche for Ni-resistant bacteria in their rhizosphere [2]. These Ni-resistant microorganisms bear strong homologies with those isolated from anthropogenically Ni-polluted ecosystems [3]. Pre-induced cells of Burkholderia 32W-2, native to serpentines of New Caledonia, showed nickel accumulation during growth [3]. Nickel transport across the cell membrane occurs in Escherichia coli [5] and Pseudomonas aeruginosa [6] under Ni induction and was found to encode a periplasmic Ni-binding protein
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