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Infection and Immunity, November 2000, p. 6182-6188, Vol. 68, No. 11
Channing Laboratory, Department of Medicine,
Brigham and Women's Hospital,1 and
Department of Microbiology and Molecular
Genetics,3 Harvard Medical School, Boston,
Massachusetts 02115, and Laboratory of Bacteriology and
Medical Mycology, Istituto Superiore di Sanita, 00161 Rome,
Italy2
Received 22 September 1999/Returned for modification 15 December
1999/Accepted 2 August 2000
A genetic approach was used to assess the heterogeneity of the
capsular polysaccharide C (PS C) biosynthesis locus of
Bacteroides fragilis and to determine whether distinct loci
contain genes whose products are likely to be involved in conferring
charged groups that enable the B. fragilis capsular
polysaccharides to induce abscesses. A collection of 50 B. fragilis strains was examined. PCR analysis demonstrated that the
genes flanking the PS C biosynthesis region are conserved, whereas the
genes within the loci are heterogeneous. Only
cfiA+ B. fragilis strains, which
represent 3% of the clinical isolates of B. fragilis,
displayed heterogeneity in the regions flanking the polysaccharide
biosynthesis genes. Primers were designed in the conserved regions
upstream and downstream of the PS C locus and were used to amplify the
region from 45 of the 50 B. fragilis strains studied.
Fourteen PS C genetic loci could be differentiated by a combination of
PCR and extended PCR. These loci ranged in size from 14 to 26 kb.
Hybridization analysis with genes from the PS C loci of strains 9343 and 638R revealed that the majority of strains contain homologs of
wcgC (N-acetylmannosamine dehydrogenase), wcfF (putative dehydrogenase), and wcgP
(putative aminotransferase). The data suggest that the synthesis of
polysaccharides that have zwitterionic characteristics rendering them
able to induce abscesses is common in B. fragilis.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Genetic Diversity of the Capsular Polysaccharide C
Biosynthesis Region of Bacteroides fragilis
*
Corresponding author. Mailing address: Channing
Laboratory, 181 Longwood Ave., Boston, MA 02115. Phone: (617) 525-2679. Fax: (617) 731-1541. E-mail:
lcomstock{at}channing.harvard.edu.
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