miércoles, 21 de enero de 2015

Tuberculosis genomes track human history

A pernicious family of TB strains emerged in Asia more than 6,000 years ago.

A study of nearly 5,000 samples of Mycobacterium tuberculosis from around the world shows how a lineage of the bacterium that emerged thousands of years ago in Asia has since become a global killer that is widely resistant to antibiotic drugs.

Although M. tuberculosis probably first emerged some 40,000 years ago in Africa, the disease did not take hold until humans took to farming — with the consequent settling down — says Thierry Wirth, an evolutionary geneticist at the National Museum of Natural History in Paris and lead author of the study.

The grouping together of people in settlements made it easier for the respiratory pathogen to spread from person to person, says Wirth. A previous analysis by his team had shown that the common ancestor of all the M. bacterium strains circulating today began spreading around 10,000 years ago in the ancient Fertile Crescent, a region stretching from Mesopotamia to the Nile Delta that was a cradle of agriculture — enabling lots of people to live in close proximity. “It’s basically a dream setting for a bug like TB,” says Wirth. [...] nature.com/