Isolation and identification of chromium-tolerant bacterial strains and their potential to promote plant growth

Abstract

Remediation and management of Chromium (Cr) contaminated soils for safe usage has been a serious challenge. The aim of present work was to isolate and identify Cr tolerant bacterial strains and assessing their plant growth promoting potential under controlled conditions. Soil samples were collected from Gujrat District, Pakistan, and analyzed for Cr content and bacteria isolation. In-vitro screening was done for chromium tolerance and plant growth-promoting (PGP) abilities. The tolerant isolates which also exhibited PGP abilities were used as inoculants in germination and pot trial experiment. The isolates A5 and A6, identified as Pseudomonas plecoglossicida and Staphylococci saprophyticus through 16S rRNA gene sequencing, were found to be tolerant up to 700 mg L-1 of Cr (VI). Both were effective in solubilizing phosphate but only A5 (Pseudomonas plecoglossicida) was able to produce indole acetic acid. A5 also increased the percentage of seed germination from 17 to 46% and spinach plant’s biomass by 44% with respect to the control. Keeping in view the results obtained, A5 (Pseudomonas plecoglossicida) appeared as the best species that was able to tolerate Cr stress and promote plant growth. Further, it can be developed as a bio-inoculant for non-food agricultural applications for remediation of Cr contaminated soils.