Current trends in capsular polysaccharide biosynthesis of Streptococcus pneumoniae

The capsular gene cluster (cap/cps) of 13 out of the 90 known pneumococcal types has been sequenced. The cap/cps operon, located between dexB and aliA in the Streptococcus pneumoniae chromosome, contains some of the genes res ponsible for the synthesis of the type-specific polysaccharide flanked by f our conserved open reading frames. The biochemical function of only a few c apsular genes has been established, whereas the role of the flanking region s is controversial. Remarkably, only one gene (tts) located outside the cap locus is required for the synthesis of type 37 capsule. Moreover, other ge nes not linked to the cap gene cluster are also needed for capsule synthesi s in pneumococcus. (C) 2000 Editions scientifiques et medicales Elsevier SA S.