Related Experiment Videos
The Haemophilus influenzae capsulation gene cluster: a compound transposon
J S Kroll1, B M Loynds, E R Moxon
1Department of Paediatrics, University of Oxford, John Radcliffe Hospital, UK.
Molecular Microbiology
|June 1, 1991
Summary
Haemophilus influenzae capsulation (cap) genes are mobilized by IS1016 insertion sequences. Gene amplification and a specific deletion in type b strains enhance capsule production, driving invasive infections.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Capsulate Haemophilus influenzae strains are phylogenetically divided into two main divisions.
- The capsulation (cap) gene cluster's genomic location and mobility are key to understanding its evolution and function.
Purpose of the Study:
- To investigate the genomic organization and mobilization of the capsulation (cap) gene cluster in Haemophilus influenzae.
- To elucidate the mechanism of cap gene amplification and its role in capsule production.
- To understand the significance of a specific deletion in the capb locus of serotype b strains.
Main Methods:
- Analysis of insertion sequence (IS)-like elements, specifically IS1016.
- Investigation of homologous recombination mechanisms.
- Characterization of gene deletions and their functional consequences.
Main Results:
- The cap gene cluster in division I strains is flanked by IS1016 elements, forming a mobile transposon.
- Unequal homologous recombination involving IS1016 repeats facilitates reversible cap gene amplification and increased capsule production.
- Serotype b strains exhibit a fixed, large direct repeat of cap genes with a 1.2 kb deletion affecting the bexA gene.
- This deletion renders capsulation dependent on the integrity of the direct repeat structure to prevent gene loss.
Conclusions:
- IS1016 acts as a mobile element enabling cap gene amplification and variation.
- The observed deletion in the capb locus of serotype b strains likely confers a biological advantage, contributing to their global prevalence and capacity to cause invasive disease.