Colonial variation inXanthomonas campestris NRRL 8-1459 and characterization

CAOMUS. M. c.. S. P. ROOOVIN. K. A. BURTON. J. E. PITTSLEY. C. A. KNUTSON. and A. JEANES. 1976. Colonial variation inXanthomonas campestris NRRL B-1459 and characterization of the polysaccharide from a variant strain. Can. J. Microbiol. 22: 942-948. Stock cultures ofXanthomonas campesrris NRRL 8-1459 require special attention to maintenance and propagation to assure consistent production in good yields of the extracellular polysaccharide xanthan. Under customary conditions ofpropagative maintenance on agar slants, variant colony types develop that are smaller in size than the normal type. The rate of regression of the normal to the variant forms was diminished when the o-glucose content of the stock medium was sufficient to avoid depletion during storage and when transfer to fresh medium was reduced to l4-day intervals. Under conditions for polysaccharide production, the normal largecolony type gives crude culture liquors after 48 h of 7000 centipoise (cp) viscosity; the predominant variant form gives only 4000 cpo On the basis of2.1 % initial o-glucose, biopolymer yields for the normal and variant strains were 62 and 43%, respectively. Polysaccharide produced by the variant (small-colony type) differs adversely in solution propenies from that of the parent strain (Iarge-eolony type): it differs also in its lower content of pyruvic acid and O-acetyl substituents. The molar ratios ofconstituent sugars (o-glucose. o-mannose. and o-g1ucuronic acid). however, were identical in polysaccharides with the normal and variant strains. Exclusion of colonial variants from fermentations is prerequisite to production of xanthan optimum in propenies and yield.