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The type 2 capsule locus of Streptococcus pneumoniae
F Iannelli1, B J Pearce, G Pozzi
1Sezione di Microbiologia, Dipartimento di Biologia Molecolare, Università di Siena, 53100 Siena, Italy.
Journal of Bacteriology
|April 10, 1999
Summary
The Streptococcus pneumoniae type 2 capsule locus in the virulent D39 strain was sequenced, revealing 18 genes potentially involved in capsule biosynthesis. Unencapsulated derivatives showed significant gene deletions.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Streptococcus pneumoniae is a significant human pathogen.
- Capsular polysaccharides are crucial virulence factors in S. pneumoniae.
- Strain D39 is a widely used virulent strain and parent for research recipients.
Purpose of the Study:
- To characterize the type 2 capsule locus of Streptococcus pneumoniae strain D39.
- To identify genes involved in capsule biosynthesis.
- To compare the capsule locus in virulent and unencapsulated strains.
Main Methods:
- Genomic DNA from strain D39 was used as a template for PCR amplification.
- A 21.7-kb PCR fragment containing the capsule locus was sequenced.
- Sequence data was analyzed to identify open reading frames (ORFs) and potential gene functions.
Main Results:
- The type 2 capsule locus of strain D39 comprises 18 open reading frames.
- Seventeen of these ORFs share the same transcriptional direction and are potentially involved in capsule biosynthesis.
- Unencapsulated derivatives (R36A and R6) possess a 7,504-bp deletion, encompassing nine capsule genes.
Conclusions:
- The characterized capsule locus provides a genetic basis for type 2 capsule production in S. pneumoniae D39.
- The identified genes are likely essential for capsule biosynthesis.
- Deletions in the capsule locus explain the unencapsulated phenotype of R36A and R6 strains.