Comparison of Exopolysaccharides Produced by Xanthomonas oryzae pv. oryzae Strains, BXO1 and BXO8 that Show Varying Degrees of Virulence in Rice (Oryza sativa L.)

The present study describes the compositional difference of the exopolysaccharide (EPS) produced by Xanthomonas oryzae pv. oryzae strains, BXO1 and BXO8 that show varying degrees of virulence in rice (Oryza sativa L.). The EPS of X. oryzae pv. oryzae strains, BXO1 and BXO8 was extracted, estimated and characterized using Fourier transform infrared, nuclear magnetic resonance (NMR), high-performance size exclusion chromatography and high-performance anion exchange chromatography (HPAEC) with pulsed amperometric detection (PAD). The 1H-NMR spectra showed the presence of a- or b-anomeric carbon of hexose or pentose, hydrogen next to hydroxyl group and uronic acid of hexose and pentose in the EPS of both BXO1 and BXO8. HPAEC with PAD revealed the presence of arabinose, galactose, glucose, mannose, galacturonic acid and glucuronic acid in both EPSs. In addition, only EPS of BXO8 contained rhamnose and xylose. The most virulent strain, BXO8 produced higher amount of EPS (43.62 lg/ml) than did BXO1 (32.5 lg/ml). Compositional difference of EPS produced by different strains of X. oryzae pv. oryzae might play an important role in host or cultivar specificity and might determine the spectrum of their virulence. Knowledge on EPS may help to understand the mode of action of bacterial pathogens.