Spontaneous sequence duplications within capsule genes cap8E and tts control phase variation in Streptococcus pneumoniae serotypes 8 and 37.
Capsule phase variants were isolated from serotype 8 and serotype 37 pneumococcal sorbarods. Sequence duplications within the essential capsule genes - cap8E (type 8) and tts (type 37) - were found to introduce frameshifts and generate acapsular phenotypes. Capsular revertants possessed wild-type cap8E and tts genes, indicating the precise excision of these duplications. Reversion frequencies (OFF-ON) fit a linear relationship between log(frequency of reversion) and log(length of duplication), previously found for serotype three pneumococci [Waite, R. D., Struthers, J. K. & Dowson, C. G. (2001). Mol Microbiol 42, 1223-1232]. This study provides evidence that capsule phase variation can occur in pneumococcal serotypes with either simple (one to three genes) or complex capsule-encoding loci (12 genes). Given the key role of CapE (the first monosaccharide transferase) in other clinically important pneumococci, such as serotypes 14 and 19F with complex capsular loci, the observed duplication within cap8E suggests that capsule phase variation could be controlled by tandem sequence duplication in capE homologues in other pneumococcal serotypes that construct their capsules through polymerization of lipid-linked intermediates.
Waite
Richard D
RD
Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK.
Penfold
David W
DW
Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK.
Struthers
J Keith
JK
Public Health Laboratory, Coventry and Warwick Hospital, Coventry CV1 4FH, UK.
Dowson
Christopher G
CG
Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK.
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D003470:Culture Media; D020440:Gene Duplication; D015964:Gene Expression Regulation, Bacterial; D014644:Genetic Variation; D006801:Humans; D008969:Molecular Sequence Data; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000235:genetics* / Q000254:growth & development
D001426:Bacterial Proteins; D003470:Culture Media; D011135:Polysaccharides, Bacterial; C121798:pneumococcal polysaccharide, type 8