IDENTIFICATION AND CHARACTERIZATION OF MYXOCOCCUS-XANTHUS MUTANTS DEFICIENT IN CALCOFLUOR WHITE BINDING

Calcofluor white is a fluorescent dye that binds to glycans and can be used to detect extracellular polysaccharide in Myxococcus xanthus and many other bacteria, We observed that an esg mutant showed less bindi ng to calcofluor white than wild-type cells, Unlike S-motility mutants that share this phenotypic characteristic, the esg mutant exhibited S motility, This led us to identify a collection of nine new transposon insertion mutants, designated Cds (for calcofluor white binding defic ient and S motile), which exhibited a phenotype similar to that of the esg strain, The Cds phenotype was found in 0.6% of the random inserti on mutants that were screened. The Cds mutants were also found to be d efective in cell-cell agglutination and developmental aggregation, Ext racellular matrix fibrils composed of roughly equal amounts of polysac charide and protein have been shown to be involved in agglutination, a nd electron microscopic examination showed that esg and the other Cds mutants lack the wild-type level of fibrils, Analysis of total M, xant hus carbohydrate demonstrated that polysaccharide content increased by about 50% when wild-type cells entered stationary phase, This inducti on was reduced or eliminated in all of the Cds mutants, The degree of polysaccharide deficiency in the Cds mutants correlated with the degre e of loss of agglutination and dye binding as well as with the severit y of the developmental aggregation defect, Preliminary genetic charact erization demonstrated that the transposon insertion mutations in thre e of the Cds mutants (SR53, SR171, and SR200) were loosely linked, The results of this study suggest that many genes are involved in the pro duction of calcofluor white binding polysaccharide material found in t he extracellular matrix and that the polysaccharide is fibrillar, Thes e results are also consistent with the findings of earlier studies whi ch indicated that fibrils function to join agglutinating cells and to form multicellular fruiting aggregates.