Journal of Applied Microbiology, Vol.108, No.2, 703-711, 2010
Purification, crystal structure and antimicrobial activity of phenazine-1-carboxamide produced by a growth-promoting biocontrol bacterium, Pseudomonas aeruginosa MML2212
Aim: To purify and characterize an antimicrobial compound produced by a biocontrol bacterium, Pseudomonas aeruginosa MML2212, and evaluate its activity against rice pathogens, Rhizoctonia solani and Xanthomonas oryzae pv. oryzae. Methods and Results: Pseudomonas aeruginosa strain MML2212 isolated from the rice rhizosphere with wide-spectrum antimicrobial activity was cultured in Kings'B broth using a fermentor for 36 h. The extracellular metabolites were isolated from the fermented broth using ethyl acetate extraction and purified by two-step silica-gel column chromatography. Three fractions were separated, of which a major compound was obtained in pure state as yellow needles. It was crystallized after dissolving with chloroform followed by slow evaporation. It is odourless with a melting point of 220-222 degrees C. It was soluble in most of the organic solvents and poorly soluble in water. The molecular mass of purified compound was estimated as 223 center dot 3 by mass spectral analysis. Further, it was characterized by IR, 1H and 13C NMR spectral analyses. The crystal structure of the compound was elucidated for the first time by X-ray diffraction study and deposited in the Cambridge Crystallographic Data Centre (http://www.ccde.com.ac.uk) with the accession no. CCDC 617344. Conclusion: The crystal compound was undoubtedly identified as phenazine-1-carboxamide (PCN) with the empirical formula of C13H9N3O. Significance and Impact of the Study: As this is the first report on the crystal structure of PCN, it provides additional information to the structural chemistry. Furthermore, the present study reports the antimicrobial activity of purified PCN on major rice pathogens, R. solani and X. oryzae pv. oryzae. Therefore, the PCN can be developed as an ideal agrochemical candidate for the control of both sheath blight and bacterial leaf blight diseases of rice.
Keywords:antimicrobial;crystal structure;phenazine-1-carboxamide;Pseudomonas aeruginosa;Rhizoctonia solani;Xanthomonas oxyzae pv;oryzae