%0 Journal Article
%T Phase variation and microevolution at homopolymeric tracts in Bordetella pertussis
%A Emily B Gogol
%A Craig A Cummings
%A Ryan C Burns
%A David A Relman
%J BMC Genomics
%D 2007
%I BioMed Central
%R 10.1186/1471-2164-8-122
%X The genomes of B. pertussis and the two closely related species, B. bronchiseptica and B. parapertussis, were screened for homopolymeric tracts longer than expected on the basis of chance, given their nucleotide compositions. Sixty-nine such HPTs were found in total among the three genomes, 74% of which were polymorphic among the three species. Nine HPTs were genotyped in a collection of 90 geographically and temporally diverse B. pertussis strains using the polymerase chain reaction/ligase detection reaction (PCR/LDR) assay. Six HPTs were polymorphic in this collection of B. pertussis strains. Of note, one of these polymorphic HPTs was found in the fimX promoter, where a single base insertion variant was present in seven strains, all of which were isolated prior to introduction of the pertussis vaccine. Transcript abundance of fimX was found to be 3.8-fold lower in strains carrying the longer allele. HPTs in three other genes, tcfA, bapC, and BP3651, varied widely in composition across the strain collection and displayed allelic polymorphism within single cultures.Allelic polymorphism at homopolymeric tracts is common within the B. pertussis genome. Phase variability may be an important mechanism in B. pertussis for evasion of the immune system and adaptation to different niches in the human host. High sensitivity and specificity make the PCR/LDR assay a powerful tool for investigating allelic variation at HPTs. Using this method, allelic diversity and phase variation were demonstrated at several B. pertussis loci.Bordetella pertussis causes whooping cough, a highly communicable disease that killed roughly 279,000 people and infected 17.6 million people globally in a recent typical year [1]. B. pertussis and the closely related human- and sheep-adapted species, B. parapertussis, have diverged independently by genome decay from a putative common ancestor that they share with B. bronchiseptica, which has a broader host range, and unlike the other two species, causes
%U http://www.biomedcentral.com/1471-2164/8/122