[Isolation, identification and characterization of rice rhizobacterium Pseudomonas aeruginosa PA1201 producing high level of biopesticide "Shenqinmycin" and phenazine-1-carboxamide].

OBJECTIVE

To identify bacterial strains with the inhibitory activity to rice pathogens, and to evaluate their potentials for the development of new biopesticides.

METHODS

Rice rhizosphere Pseudomonas strains were isolated using 1-aminocyclopropane-1-carboxylic acid as the sole carbon source. Strain PA1201 was further identified through morphological analysis, biochemical characterization, 16S rDNA sequence analysis and phospholipid fatty acid profiling. Qualitative and quantitative analysis of the production of the green pesticide Shenqinmycin as well as phenazine-1-carboxamide produced by PA1201 was done by HPLC. Cytotoxicity of PA1201 was evaluated using human alveolar epithelial cell line A549 and Drosophila melanogaster as hosts.

RESULTS

Strain PA1201 inhibited Rhizotonia solani Kuhn and Xanthomonas oryzae pv. oryzae, the causal agents of rice sheath blight and bacterial blight, respectively. It was further identified as Pseudomonas aeruginosa PA1201, which produces shenqinmycin and phenazine-1-carboxamide. The fermentation titer of shenqinmycin and phenazine-1-carboxamide in the PPM medium was 81.7 mg/L and 18. 1 mg/L, respectively. In the medium supplemented with soybean meal and corn steep liquor, the level of shenqinmycin and phenazine-1-carboxamide reached 926. 9 mg/L and 489. 5 mg/L. PA1201 also produced high level of extracellular protease and was toxic to human cell line and fruit fly.

CONCLUSION

Strain PA1201 could be engineered for higher yield of Shenqinmycin or for a new biopesticide.