Muhammad Naees, Qurban Ali, Muhammad Shahbaz, Fawad Ali
Heavy metal pollution of soil is a significant environmental problem and has its negative impact on human health and agriculture. Rhizosphere, as an important interface of soil and plant, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria have received more and more attention. A heavy metal-resistant bacterial strain was isolated from heavy metal-contaminated soils and identified as Burkholderia sp. J62 based on the 16S rDNA gene sequence analysis. Strain J62 was able to colonize and develop in the rhizosphere soil of maize and tomato after root inoculation and was able to promote the growth of maize and tomato. The application of strain J62 effectively increased the bioavailability of Pb and Cd in the rhizosphere soils and promoted the growth of maize and tomato plants, consequently increasing the total Pb and Cd uptakes of the plants even under nonsterile conditions. The isolate was found to exhibit different multiple heavy metal and antibiotic resistance characteristics. Inoculation with the isolate was found to increase the biomass of maize and tomato plants. Increase in tissue Pb and Cd contents varied from 38 to 192% and from 5 to 191% in inoculated plants growing in heavy metal-contaminated soils compared to the uninoculated control, respectively. Phytoremediation could clean up the heavy metal-contaminated soil. In addition, although strain J62 significantly increased the Pb and Cd uptakes by the maize and tomato, the total Pb and Cd accumulation of the plants is low.
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