Chromium reducing and plant growth promoting novel strain Pseudomonas aeruginosa OSG41 enhance chickpea growth in chromium amended soils

Pseudomonas aeruginosa strain OSG41, isolated from the heavy metal contaminated water irrigated to rhizospheric soil of mustard crop, tolerated chromium up to the concentration of 1800 μg ml−1 and reduced it by 100% at pH 6–8 after 120 h incubation at 30–40 °C. P. aeruginosa produced plant growth-promoting substances, both in the presence and absence of chromium; it produced 32 μg ml−1 indole acetic acid ml−1, in Luria Bertani broth with 100 mg tryptophan ml−1, solubilized tri-calcium phosphate (417 μg ml−1) and secreted 20.8 μg ml−1 exopolysaccharides (EPS) which decreased with increasing concentration of chromium added to growth medium. While investigating the impact of hexavalent chromium on chickpea, chromium application to soil had a phytotoxic effect. The application of P. aeruginosa strain OSG41 even with three times concentration of chromium increased the dry matter accumulation, symbiotic attributes (like nodule formation), grain yield and protein of chickpea compared to non-inoculated plants. The bio-inoculant decreased the uptake of chromium by 36, 38 and 40% in roots, shoots and grains, respectively. The present finding suggests that the bioinoculant effectively reduced the toxicity of hexavalent chromium to chickpea plants and concurrently enhanced the biological and chemical characteristics of chickpea, when grown in chromium treated soils.

► Heavy metal tolerance and hexavalent chromium reduction by P. aeruginosa.
► Construction of phylogenetic tree with accession No. HM222648.1. of P. aeruginosa.
► Testing of strain OSG41 for chickpea crop improvement.
► Role of EPS in plant microbe interaction/stress alleviation.
►  Maintenance of free proline level in plant tissues by strain OSG41 of P. aeruginosa.