Bacterial strain identified as Klebsiella pneumoniae SK1, based on 16S rDNA sequence study, was isolated from a textile mill discharge point at Dada Nagar industrial area in Kanpur, India in media containing 100 µg/ml each of disulfonated azo dye Acid Red 249 (AR) and hexavalent chromium [Cr(VI)]. SK1 is efficient in the concomitant decolorization and reduction of 100 µg/ml toxic AR and Cr(VI) respectively in 48 h under microaerophilic conditions. The efficacy of AR decolorization was found to be preeminent in static conditions, 37°C, 2-4% salinity and 7-9 pH range. 99% decolorization for initial AR concentration of 100 µg/ml in 48 h, and 91% for 250 µg/ml and 77% for 500 µg/ml was recorded in 72 h respectively in the presence of 100 µg/ml Cr(VI). Significant reductive changes in spectroscopic absorption spectra were observed for SK1 treated AR+Cr(VI) amended media with respect to controls. FITR spectroscopy was used to ascertain the breakage of the azo dye bond and the formation of biodegradative metabolites. Additionally, SK1 was found to be positive for indole acetic acid, ammonia, phosphate and potassium solubilization and biofilm formation. In plant bioassay, in vitro SK1 treated AR+Cr(VI) TSB media was used to treat Triticum aestivum in the soil environment. In comparison to untreated control, plants treated with bioremediation media shows increased percent germination, root and shoot length with a complete reversal of phytotoxic effects of the AR+Cr(VI) treated plants. In this study, environmental K. pneumoniae SK1 shows concomitant azo dye and Cr(VI) remediation with plant growth-promoting activity.
Acid red azo dye and Cr(VI) bioremediation, Plant growth promotion, Klebsiella pneumoniae, Phytotoxicity
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