Production of indole acetic acid by a novel bacterial strain of Planomicrobium chinense isolated from diesel oil contaminated site and its impact on the growth of Vigna radiata

Abstract

A novel bacterial strain of Planomicrobium chinense (B6) degrading diesel oil [2.5% (v/v)] within 96 h was evaluated for influencing the growth of Vigna radiata under increasing concentrations of diesel from 0.5 to 2.5% (v/v). The strain was investigated for the production of plant growth promoting factors viz., Indole acetic acid, ammonia and phosphate solubilization under the influence of diesel oil. The IAA activity was augmented at 0.75 mM tryptophan and low concentrations of diesel oil [0.5–1.5% (v/v)]. The seeds treated with P. chinense (seed imbibement) as well as by soil inoculation showed significant enhancement of plant biomass and hydrocarbon degradation as compared to control treatment. However, seeds grown on soil previously inoculated with the organism performed better than those applied by seed imbibement. Increase in plant biomass were optimized at low concentrations of diesel oil [0.5–1% (v/v)]. Gas chromatography of the bacterial inoculated soil revealed degradation of most of the linear chain alkanes along with a simultaneous increase in the plant biomass. Production of plant growth promoting factors and increase in plant biomass yield in the presence of diesel oil provides a conception of the efficiency of P. chinense for plant growth promotion activities besides hydrocarbon degradation in diesel contaminated sites.