Isolation and characterization of rhizobacteria from lentil for arsenic resistance and plant growth promotion.

Abstract

Low-cost microbial remediation strategies serve as a viable and potent weapon for curbing the arsenic menace. In the present study, two arsenic-resistant bacteria were isolated from the contaminated lentil rhizosphere in Gangetic plain of eastern India. LAR-21 (Burkholderia cepacia, MW356875) and LAR-25 (Burkholderia cenocepacia, MW356894) could remove 87.6% and 85.9% of arsenite (10mM) from the liquid culture medium in laboratory condition. They were highly resistant to arsenate and arsenite and also had a high arsenite oxidase activity. LAR-21 showed the highest level of minimum inhibitory concentration value of 390mM for arsenate and 31mM for arsenite. The same strain was found to show highest arsenite oxidase activity, i.e., 5.2nMmin-1mg-1of protein. These two strains further possess potential plant growth-promoting characteristics like indole acetic acid production (5-15mMIAAmL-1), 1-aminocyclopropane-1-carboxylate deaminase (8-21nMα-ketobutyratemgprotein-1h-1), nitrogenase activity (3-8.99nMethylenemgcellprotein-1h-1), siderophore production (17-22.1µMdeferoxaminemesylatemL-1), phosphate solubilization (261-453µgmL-1) under arsenic stress condition. The plant growth promotion of the strains was further validated by pot study of lentil by assessing their agronomic and growth-related traits, and potential to recover from arsenic stress (17.2-21.2% arsenic reduction in root and shoot, 16-19.2% in leaf and pod, and 15-23% reduction in seeds). The LAR-21 strain, thus, emerged as the most suited candidate for bioremediation and plant (lentil) growth promotion in arsenic polluted environment.