Screening of Cadmium-Resistant Microbes to Improve the Tolerance of Sorghum bicolor (L.) Moench Against Cadmium

To improve the cadmium (Cd) resistance and the remediation ability of Sorghum bicolor (L.) Moench, fourteen Cd-resistant bacteria were screened from cadmium-contaminated soil, together with two strains preserved in the laboratory. It was found that 3 strains (ZR451, ZR452, and ZJSH1) significantly promoted the growth of Cd-stressed S. bicolor in hydroponics and mitigated Cd toxicity to plants, and SR8, ZRK1, and ZR211 promoted sorghum growth lightly. Further studies indicated that strains SR8, ZR211, and ZJSH1 were Cd-resistant and acid-resistant strains. Strains ZR211and ZR121 significantly produced two hormones (SA and GA), ZJSH1 significantly produced IAA and SA, and strains SR8, ZR451 and ZR452 produced one hormone. Strains SR8, ZR451, ZR452, and ZJSH1 produced siderophores. In addition, strain ZJSH1fixed nitrogen and produced ACC deaminase, while ZR451 and ZJSH1 solubilized phosphorus Correlation analysis showed that the Cd resistance of the strains was significantly and positively correlated with their IAA and GA production. The screening of the three cadmium resistant strains ZJSH1 (Sphingomonas paucimobilis), ZR451 (Bacillus cereus) and ZR452 (Bacillus cereus) provided bacterial resources for the efficient remediation of Cd-contaminated soils by bacterial - S. bicolor combination.