Bioremediation of Arsenic and Cadmium by Metal-Resistant Bacteria in Spinach

Five previously reported isolates Serratia liquefaciens BSWC3, Pantoea dispersa KDWC1, Klebsiella pneumoniae RpSWC3, K. quasipneumoniae RgCWC2 , and Enterobacter mori RgUWC1 were selected from previous studies to check their bioremediation efficiency of arsenic and cadmium removal in Spinach. All the selected cadmium-tolerant bacterial strains were also able to tolerate sodium arsenate. However, only two strains, S. liquefaciens BSWC3 and E. mori RgUWC1, were able to bear a concentration of 300 mM sodium arsenate. A pot culture experiment was setup during the Rabi season with seven treatments to evaluate the bioremediation of arsenic and cadmium in spinach. The most of the plant growth traits (seed germination, plant height, root and shoot fresh and dry weight, N-fixation and colony-forming unit) were maximum in the treatment (RgUWC1 + cadmium) ; however, maximum root lengths were recorded where seeds were inoculated with BSWC3 + arsenic. Atomic absorption spectroscopy study revealed that the Cd-tolerant bacterial strains BSWC3 and RgUWC1 showed a significant reduction in arsenic and cadmium concentration, i.e., 64.01% and 57.319%, respectively, as compared to control. Results revealed that these bacterial isolates or their metal-resistant gene pool can be useful for reduction of metal toxicity in leafy vegetable like spinach.