Whooping cough gene loss

1 November 2003

Bordetella pertussis, the bacterium responsible for whooping cough, appears to have undergone a dramatic loss of genes during its evolution, removing its ability to infect hosts other than humans.

Researchers at the Wellcome Trust Sanger Institute, in collaboration with colleagues in Cambridge, UK, Madison and Berlin, compared the genome sequence of B. pertussis with those of B. bronchiseptica, which causes minor respiratory tract ailments in a wide range of animals and is the presumed ancestor of B. pertussis, and B. parapertussis, a close relative that infects only humans and sheep, and is a less common cause of whooping cough.

The comparisons suggest that it is loss of genes by B. pertussis and B. parapertussis, rather than gain of genes by B. bronchiseptica, that underlies the restricted host range of the human pathogens. Moreover, the particularly detrimental effects of B. pertussis also appear to be due to gene loss rather than gain - the bacterium has not gained genes making it more virulent, but appears to have lost factors that used to control its virulence.

It is possible, the researchers suggest, that the rapid growth in human populations over the past few millennia have created conditions in which rapid spread of the pathogen is of greater advantage than minimizing harm to the host. A better understanding of the virulence-control mechanisms that have been lost could eventually lead to new agents to combat a pathogen still responsible for more than 250 000 deaths a year.

The sequence comparisons are published in Nature Genetics, 10 August 2003 (Vol. 35: 32-40).

External links

• Comparative analysis of the genome sequences of Bordetella pertussis, Bordetella parapertussis and Bordetella bronchiseptica, Nature Genetics 35, 32-40 (10 August 2003)
• Wellcome Trust Sanger Institute