Sequencing pathogens: got the bug?

Sequencing work is boosting our ability to understand and exploit pathogens.

Sequencing pathogens has always been a key aim of genomics. The very first free-living organism to be sequenced, Haemophilus influenzae, is a bacterium that can cause pneumonia and meningitis, particularly in children.

Since then, the genomes of pathogens that cause many of the word’s most devastating diseases have been sequenced, often many times over. These include tuberculosis, malaria, leprosy, plague, leishmaniasis, whooping cough, meningitis, infant diarrhoea, typhoid fever, pneumonia and many others.

Developing therapies

The sequences of pathogen genomes give us a vast amount of information about how pathogens cause disease, and how they evolve. More than that, they give us the description of the targets of antibiotics and other drugs, and tell us how bugs can become resistant to these. They also show us all the possible vaccine candidates, and tell us how much they vary, and therefore how effective they are likely to be.

Armed with this information, drug and vaccine design has the potential to become more systematic and comprehensive. Recently, for example, a new vaccine has been developed against Type B Neisseria meningitis, which can cause meningitis, based on the genome sequence of the organism, and this is currently being trialled.

Antibacterial drugs need no longer be found by trial and error. Knowing all the genes, and hence the proteins, in a particular bacterium, ought to make designer drugs possible.

Aids for agriculture

Genome information is being used to study other aspects of disease organisms, such as interactions between hosts and pathogens. This is useful in agriculture as well as human medicine. For example, the bacterium Xyella fastidiosa destroys grape vines and orange trees. Its genome was sequenced in 2000 by a team of Brazilian scientists, and is being used to find ways to attack the disease. Bacteria that cause diseases in potatoes and sugar cane have also been sequenced in recent years.

Recent work on bee genomes suggests that the widespread collapse of bee colonies is due to the presence of small RNA viruses copied into their DNA, which makes bees less resistant to disease.

Image: Haemophilius influenzae; Wellcome Images

Thanks to Professor Julian Parkhill, Wellcome Trust Sanger Institute.

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