GENETIC AND MOLECULAR CHARACTERIZATION OF CAPSULAR POLYSACCHARIDE BIOSYNTHESIS IN STREPTOCOCCUS-PNEUMONIAE TYPE-3

To achieve a better understanding of the genetics of capsular polysacc haride synthesis in Streptococcus pneumoniae, we have identified and c haracterized mutants deficient in type 3 capsule production. We identi fied a clone that restored encapsulation in one of our mutants and in a mutant deficient in UDP-glucose dehydrogenase. By hybridization, we developed a chromosomal map of the type 3-specific region and identifi ed a flanking region containing DNA common to all capsule types examin ed. Insertion mutations were used to identify chromosomal loci require d for capsule synthesis, and to map transcription within the region. U sing non-destructive insertions linked to type-specific genes of type 2, 3, or 5, we were able to select for the transformation of all neces sary genes specific for capsule type. Our data provide molecular evide nce to show that all the type-specific genes are linked in a cassette and can be transferred as a unit during transformation.