Genes Involved in Haemophilus influenzae Type b Capsule Expression are Part of an 18-Kilobase Tandem Duplication

Encapsulated Haemophilus influenzae type b produce nonencapsulated variants at high frequency (0.1-0.3%). Cosmid cloning was used to investigate the genetic mechanism responsible for this instability. Analysis of three independently derived cosmid clones showed that the b+ parental strain contains a...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1986-02, Vol.83 (4), p.1106-1110
Main Authors: Hoiseth, Susan K., Moxon, E. Richard, Silver, Richard P.
Format: Article
Language:English
Subjects:
Bacteriology
Biological and medical sciences
Capsules
Chromosome Mapping
Chromosomes, Bacterial
Cloning, Molecular
Cosmids
DNA
DNA probes
DNA Restriction Enzymes
Escherichia coli - metabolism
Fundamental and applied biological sciences. Psychology
Gels
Gene Expression Regulation
Genes
Genes, Bacterial
Genetic mutation
Genetic screening
Genetics
Haemophilus influenzae - genetics
Haemophilus influenzae - metabolism
Haemophilus influenzae type b
Microbiology
Plasmids
Polysaccharides, Bacterial - biosynthesis
Rec A Recombinases - physiology
Recombination, Genetic
Repetitive Sequences, Nucleic Acid
Transformation, Bacterial
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Summary:Encapsulated Haemophilus influenzae type b produce nonencapsulated variants at high frequency (0.1-0.3%). Cosmid cloning was used to investigate the genetic mechanism responsible for this instability. Analysis of three independently derived cosmid clones showed that the b+ parental strain contains an 18-kilobase tandem duplication of genes involved in type b capsule expression. Loss of one complete copy of the 18-kilobase tandem duplication occurred following transformation of the cosmid clones into Rec+, but not Rec-, Escherichia coli, and in H. influenzae strains that had spontaneously lost capsule expression. These results suggest that high-frequency loss of type b capsule expression is due to rec-dependent recombination between the two copies of the 18-kilobase tandem repeat. This is further supported by our finding that introduction of the H. influenzae rec-1 mutation stabilized type b capsule expression.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.83.4.1106