DIFFERENTIATION OF CAPSULAR POLYSACCHARIDES FROM ACETOBACTER-DIAZOTROPHICUS STRAINS ISOLATED FROM SUGARCANE

Capsular polysaccharides (CPSs) from six representative strains of Ace tobacter diazotrophicus were isolated and fractionated by gel filtrati on and anion-exchange chromatography, Purified CPSs obtained in the no n-adsorbed fraction of a DEAE-Sephadex A-25 column were qualitatively and quantitatively analyzed for sugar composition, Uronic acid and ami no sugars were not detected in all purified CPSs, Basically the CPSs o f A. diazotrophicus are composed of rhamnose, mannose, galactose and g lucose. The presence of fucose was only observed in the CPS of strains PR2 and PAL3, Based on these results, the six strains of A. diazotrop hicus could be divided into four groups according to the sugar content of their capsules: (i) fucose-containing capsules (PR2 and PAL3, loca lized in roots), (ii) mannose-rich capsule (PALS, localized in root), (iii) capsules with a high ratio of hexose to rhamnose (PR4 and PR20, localized in stems) and (iv) capsules with a low ratio of hexose to rh amnose (PR14, localized in rhizosphere), For all CPSs, sodium dodecy s ulfate-polyacrylamide gel electrophoresis showed diffuse bands of slow mobility in silver-stained gels, The different CPS migration patterns could not be correlated with sugar composition. The purified CPS of s train PAL3 was found to be immunogenic and immunochemically similar to the CPS of strain PR2. The serological specificity to CPS of strains PAL3 and PR2 correlated well with the presence of fucose, indicating t hat this deoxyhexose is immunodominant. These findings demonstrated th e feasibility of preparing specific antibodies to fucose-containing CP S of A. diazotrophicus, indicating the possibility of utilization of t his antiserum for future taxonomic studies or to select strains with c hemically related capsular polysaccharides from their natural habitat.