Effects of inoculation of biosurfactant-producing Bacillus sp. J119 on plant growth and cadmium uptake in a cadmium-amended soil

A biosurfactant-producing Bacillus sp. J119 isolated from heavy metal contaminated soils was investigated for its effects on the plant growth-promoting characteristics and heavy metal and antibiotic resistance. A pot experiment was conducted for investigating the capability of the biosurfactant-producing bacterial strain Bacillus sp. J119 to promote the plant growth and cadmium uptake of rape, maize, sudangrass and tomato in soil artificially contaminated with different levels of cadmium (Cd) (0 and 50 mg kg−1). The strain was found to exhibit different multiple heavy metal (Pb, Cd, Cu, Ni and Zn) and antibiotic (kanamycin, streptomycin, ampicillin, tetracycline and rifampin) resistance characteristics. The strain had the capacity to produce indole acetic acid (IAA) and siderophores. Cd treatment did not significantly decreased growth of tomato, maize and rape plants, but Cd treatment significantly decreased growth of sudangrass (p < 0.05). In the Cd-added soil, above-ground biomass and root dry weights of tomatoes were increased by 24 and 59%, respectively, in live bacterial inoculation compared to dead bacterial inoculation control. There were no obvious differences in the above-ground tissue and root dry weight of maize and sudangrass between live bacterial inoculation and dead bacterial inoculation. In the soil treated with 50 mg Cd kg−1, increase in above-ground tissue Cd content varied from 39 to 70% in live bacterium-inoculated plants compared to dead bacterium-inoculated control. In addition, among the inoculated plants, tomato was the greatest Cd accumulator. The bacterial strain was also able to colonize and develop in the rhizosphere soils after root inoculation.