Screening of Chromium-Resistant Bacteria for Plant Growth-Promoting Activities

Chromium-resistant plant growth-promoting bacteria (PGPB) were isolated from the electroplating industry waste disposal site soils at Coimbatore, India, using LB medium. The strain tolerated chromium concentrations up to 500mg Cr6+L-1 on LB medium. The strain was identified as Pseudomonas sp. VRK3 based on its morphological, physiological, and biochemical characteristics following Bergey's manual of determinative bacteriology. Evaluation of plant growth-promoting parameters revealed the intrinsic ability of the strain for the production of indole-3-acetic acid (IAA), siderophore, and solubilization of insoluble phosphate. Pseudomonas sp. VRK3 utilized tryptophan as a precursor for the growth and production of IAA (105.77g mL(-1)) and also exhibited the production of siderophore. The strain utilized tricalcium phosphate as the sole source of phosphate exhibiting a high rate of phosphate solubilization (0.49g mL(-1)). Pseudomonas sp. VRK3 showed a significant extent of chromium uptake and accumulation in their cell walls. Furthermore, Pseudomonas sp. VRK3 was demonstrated to possess mobilization of chromium from the soil that would enhance chromium availability to the plant. Potential use of this Pseudomonas sp. VRK3 as PGPB needs further testing in enhancing the growth and chromium uptake by the plants in pots under nursery conditions.