The Versatility of Delftia sp. Isolates as Tools for Bioremediation and Biofertilization Technologies

Two Pb(II)-resistant bacteria isolated from a soil containing 2,500 mg/kg of Pb were identified by 16S rRNA sequencing analysis as Delftia sp. and designated as 3C and 6C. Both isolates grew at a Pb(II) concentration of 62 mg/L and at the stationary phase showed a Pb(II)-sorption capability of 10 ± 1.5 (3C) and 5 ± 0.8 (6C) mg/g of biomass. Biochemical properties related to heavy metal resistance and plant growth promotion were analyzed and compared with the Cr(VI)-resistant plant growth-promoting Delftia sp. JD2, previously reported by our group. Both isolates and JD2 were resistant to Cr(VI), Pb(II) and many antibiotics, produced siderophores and the phytohormone indole-3-acetic, and showed clover growth-promoting activity in greenhouse conditions. Interestingly, the occurrence of integron class 1 was shown in all isolates. Our results add to previous reports and suggest that bacteria of the genus Delftia could be consider as good candidates for the design of technologies for cleaning up contaminated environments and/or the production of biofertilizers.