Characterization of plant growth promoting feature of a neutromesophilic, facultatively chemolithoautotrophic, sulphur oxidizing bacterium Delftia sp. strain SR4 isolated from coal mine spoil

Abstract

A new facultative chemolithoautotrophic heavy metal resistant sulfur-oxidizing bacterium was isolated from spoil sample of an open cast coal mine. FESEM demonstrated that the bacterium from Delftia genus was rod-shaped mucoid and motile. It autotrophically oxidized 20 mM thiosulfate and 1 g l−1 elemental sulfur to 220 mg l−1 and 203 mg l−1 of sulfate, respectively in 7 days under oxic condition and was also able to grow heterotrophically. The strain showed many plant growth promoting properties like production of IAA (23 ug ml−1), ammonia (6 umol ml−1), siderophore (55% siderophore unit), and HCN (30 ppm) upon 48 hours of incubation. In Pikovskaya’s agar, the strain showed phosphate solubilization index of 2.0 and solubilized tri-calcium phosphate (232 ug ml−1) and lowered pH from 8.0 to 4.5 within 18 days. The strain yielded promising results on Brassica juncea growth and sulfur, phosphorus, and lead uptake. Where sulfur and phosphorous accumulation was 52 and 116% higher in whole treated plants (derived from microbe-coated seeds), lead accumulation were 81 and 50% higher in shoot and root of the treated plants than control plants (derived from untreated seeds) . These results point that this multifunctional strain can be proposed for phytorestoration of heavy metal contaminated sites.