Survival of the not-so-fit

Bordetella pertussis, B. parapertussis, and B. bronchiseptica are three related pathogens that cause whooping cough and other respiratory diseases in humans and animals. One hypothesis to explain the relationship among the disease agents is that acquisition of genes leads to a gain of function that confers specificity of host and symptoms on a particular species. In the August 10 Nature Genetics, Julian Parkhill and colleagues, based at the Sanger Institute, show by sequencing and comparison of the genomes of all three pathogens that it is a loss of genes and regulatory elements that has caused relatively recent independent derivations of B. pertussis and B. parapertussis from B. bronchiseptica, following rearrangements and insertions by insertion sequence elements (ISEs) in their genomes (Nature Genetics, DOI:10.1038/Ng1227, August 10, 2003).

Parkhill et al. demonstrated this in part by the presence of unique gene sequences in B. bronchiseptica, the absence...