Abstract: A uranium-resistant and plant growth-promoting bacterial strain was isolated from the root of a native Rumex acetosa in a uranium mining by enrichment culture and LB plate. Its growth characteristics and the performance of plant growth-promoting under different experimental conditions were analyzed by characteristic reaction and average absorbance method. The results showed that the strain grew well at the uranium concentration of 350 mg/kg,it produced indole-3-acetic acid（IAA）and IAA reached 40.21 mg/L in 24 h at normal condition. The optimal condition for IAA production was the temperature 30℃,pH 7,rotating speed 150 r/min,yeast extract as nitrogen source,and glycerol as carbon source. The strain also had deaminase capacity of ACC,and ACC enzymatic activity was 0.32 U/μg for 24 h at normal condition. The optimal condition for ACC enzyme activity was temperature 35℃,pH 7,and rotating speed 180 r/min. The strain was identified as Achromobacter xylosoxidans while combined morphological characteristic with physiological and biochemical preliminary characteristics and 16s rDNA sequence. Dry biomass of Medicago sativa increased by 17.9%-110.4% and U was enriched by 12.2%-180.6% under different U concentration.

Key words: uranium, plant growth promoting rhizobacteria, Achromobacter xylosoxidans, growth promoting characteristics