Characterization of Serratia sp. K1RP-49 for application to the rhizoremediation of heavy metals

Many soil sites in industrialized areas are contaminated with high concentrations of heavy metals. These pollutants are highly accumulated to ecosystem and human body and cause serious ecotoxical effects. To remove heavy metals from the soil, a potential strategy is the ecologically sound, safe, and cost effective rhizoremediation using the symbiotic relationship of plants and microbes in the rhizosphere. Serratia sp. K1RP-49 was isolated from the rhizoplane of the barnyard grass (Echinochloa crus-galli) which had grown in oil contaminated soil. Serratia sp. K1RP-49 could produce various organic acids such as oxalic acid (174 mg l^-1), maleic acid (137 mg l ^-1), citric acid (15 mg l^-1), malic acid (2 mg l ^-1), formic acid (117 mg l^-1), acetic acid (79 mg l ^-1), and succinic acid (203 mg l^-1). The pH of the culture broth was decreased due to the accumulation of these organic acids. This bacterium could produce a indole acetic acid and a siderophore(s). The K1RP-49 had a moderate resistance of Pb. The results of root elongation assay indicated that the growth of radicular root of maize could be enhanced by the inoculation of Serratia sp. K1RP-49.