ABSTRACT
The antagonistic activity of three Pseudomonas fluorescens strains against Azospirillum spp. was investigated. Data revealed that Pseudomonas fluorescens strain A was the most potent against Azospirillum lipoferum when grown on 523 agar medium, with initial pH of 7.0 and incubation for one day at 30C. Extraction of Pseudomonas fluorescens strain A active ingredient was achieved by using acetone followed by diethyl ether. Using paper chromatography technique, an antibiotic was obtained as purified yellowish brown amorphous powder. It is soluble in methanol, acetone, ethyl acetate, n-butanol, diethyl ether and chloroform. The physicochemical characteristics, i.e., melting point, ultraviolet spectra [UV], infrared spectra [IR], color reactions, the 1H nuclear magnetic resonance [1H-NMR], mass spectra and elemental analysis are given. The purified antibiotic exerted a sharp melting point at 126C, the UV absorption spectra was maximum at 245 [sh] nm in ethylacetate, the molecular weight was found to be 279. Relative abundance [RA], 9.9% and elemental analysis of the antibiotic revealed that the antibiotic substance contains carbon 81.7%, hydrogen 7.5%, oxygen 5.7% and nitrogen 5.0%. The molecular formula of the antibiotic was proposed to C19H21NO based on the MS spectra and elemental analysis