Rhizoremediation of diesel-contaminated soil using the plant growth-promoting rhizobacterium Gordonia sp. S2RP-17.

A plant growth-promoting rhizobacterium (PGPR) was isolated and identified as Gordonia sp. S2RP-17, which showed ACC deaminase and siderophore synthesizing activities. Its maximum specific growth rate was 0.54 ± 0.12 d(-1) at 5,000 mg L(-1) of total petroleum hydrocarbon (TPH), and its maximum diesel degradation rate was 2,434.0 ± 124.4 mg L(-1) d(-1) at 20,000 mg L(-1) of TPH. The growth of Zea mays was significantly promoted by the inoculation of Gordonia sp. S2RP-17 in the diesel-contaminated soil. Measured TPH removal efficiencies by various means were 13% by natural attenuation, 84.5% by planting Zea mays, and 95.8% by the combination of Zea mays and Gordonia sp. S2RP-17. The S2RP-17 cell counts were maintained at 1 × 10(6) CFU g-soil(-1) during the remediation period, although they slightly decreased from their initial numbers (2.94 × 10(7) CFU g-soil(-1)). These results indicate that rhizoremediation using both Zea mays and Gordonia sp. S2RP-17 is a promising strategy for enhancing remediation efficiency of diesel-contaminated soils.