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Infection and Immunity, March 2001, p. 1244-1255, Vol. 69, No. 3
Department of Microbiology, The University of
Sydney, Sydney, New South Wales 2006, Australia
Received 19 April 2000/Returned for modification 13 July
2000/Accepted 18 September 2000
Capsular polysaccharide (CPS) is a major virulence factor in
Streptococcus pneumoniae. CPS gene clusters of S. pneumoniae types 4, 6B, 8, and 18C were sequenced and compared
with those of CPS types 1, 2, 14, 19F, 19A, 23F, and 33F. All have the
same four genes at the 5' end, encoding proteins thought to be involved in regulation and export. Sequences of these genes can be divided into
two classes, and evidence of recombination between them was observed.
Next is the gene encoding the transferase for the first step in the
synthesis of CPS. The predicted amino acid sequences of these first
sugar transferases have multiple transmembrane segments, a feature
lacking in other transferases. Sugar pathway genes are located at the
3' end of the gene cluster. Comparison of the four
dTDP-L-rhamnose pathway genes (rml genes) of
CPS types 1, 2, 6B, 18C, 19F, 19A, and 23F shows that they have the
same gene order and are highly conserved. There is a gradient in the nature of the variation of rml genes, the average pairwise
difference for those close to the central region being higher than that
for those close to the end of the gene cluster and, again,
recombination sites can be observed in these genes. This is similar to
the situation we observed for rml genes of O-antigen gene
clusters of Salmonella enterica. Our data indicate that the
conserved first four genes at the 5' ends and the relatively conserved
rml genes at the 3' ends of the CPS gene clusters were
sites for recombination events involved in forming new forms of CPS. We
have also identified wzx and wzy genes for all
sequenced CPS gene clusters by use of motifs.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.3.1244-1255.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Molecular Characterization of Streptococcus
pneumoniae Type 4, 6B, 8, and 18C Capsular Polysaccharide
Gene Clusters
*
Corresponding author. Mailing address: Department of
Microbiology (G08), The University of Sydney, Sydney, NSW 2006, Australia. Phone: (612) 9351-2536. Fax: (612) 9351-4571. E-mail:
reeves{at}angis.usyd.edu.au.
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