Inoculation of chromium-tolerant bacterium LBA108 to enhance resistance in radish ( L.) and combined remediation of chromium-contaminated soil.

Cr(VI) has been a carcinogen for organisms and a hazard to human health throughout the food chain. To explore a cost-effective and efficient method for removing Cr(VI), a Cr-resistant strain named LBA108 was isolated from the soil of a molybdenum-lead mining area. It was identified as through biochemical tests and 16S rDNA sequence analysis. Following 48 hours of incubation in LB culture medium containing 60 mg L Cr(VI), the LBA108 strain exhibited reduction and adsorption rates for Cr(VI) at 96.64% and 15.86%, respectively. The removal mechanism was subsequently confirmed through Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction analysis. In an experimental setup, radish seedlings were cultivated as test crops under varying levels of Cr stress (ranging from 0 to 7 mg L) in a hydroponic experiment. With the inoculation of the LBA108 strain, the fresh weight of radish seedlings increased by 2.05 times and plant length increased by 34.5% under 7 mg L Cr stress. In addition, the plant produced more antioxidant enzymes/enhanced antioxidant enzyme activities such as superoxide dismutase and catalase to prevent oxidative stress. Under Cr stress (6 mg L), the accumulation of Cr in rhizomes of radish seedlings increased compared to the control group by 91.44%, while the absorption of Cr by leaves decreased by 52.10%. These findings suggest that the LBA108 strain possesses bioremediation capabilities as a microbial-phytoremediation option for Cr-contaminated soil.