Chromium-reducing and phosphate-solubilizing Achromobacter xylosoxidans bacteria from the heavy metal-contaminated soil of the Brass city, Moradabad, India

• DOI: 10.1007/s13762-019-02300-y
• Publication Date: 2019-03-12T12:58:09Z
• Authors: M. Oves; M. S. Khan; H. A. Qari
• Keywords: Achromobacter xylosoxidans; Phosphate solubilizing bacteria

Chromium contamination in soil and water bodies is increasing predominantly due to inappropriate discharge from industries, and it is causing severe environmental problems and soil infertility. To improve soil quality, the sustainable approach needs to identify specific microbes capable of reducing chromium toxicity, enhancing soil P pool and expressing multiple plant growth-promoting activities. In the current investigation, a microbial strain OS2 was recuperated from polluted soil and was characterized by employing biochemical and molecular methods. Bacterial strain OS2 was identified as Achromobacter xylosoxidans by 16S rRNA quality sequencing, BLASTn, and phylogenetic examination. Strain OS2 survived well at high doses of heavy metals: Cr, Ni, Cu and Zn. A. xylosoxidans could solubilize up to 363 µg mL−1 tricalcium phosphate and reduced 100 µg mL−1 chromium after 24-h incubation. SEM and EDX analyses showed the highest accumulation of phosphate and binding with chromium up to 10.22 and 1.09 weight percent of total weight, respectively. A. xylosoxidans significantly produced IAA (26 µg mL−1) when grown up within 100 µg mL−1 chromium, as detected by HPLC. Further, strain OS2, when used as a microbial inoculant, decontaminated the chromium and concurrently improved the growth of mung bean plants while growing under metal stress conditions significantly in a sustainable manner.