Mycobacterium tuberculosis: Our African follower for over 70,000 years!

September 01, 2013

Tuberculosis (TB) remains one of deadliest infectious diseases of humans, killing 50% of individuals when left untreated. Even today, TB causes 1-2 million deaths every year mainly in developing countries. Multidrug-resistance is a growing threat in the fight against the disease.

An international group of researchers led by Sebastien Gagneux from the Swiss Tropical and Public Health Institute (Swiss TPH) has now identified the origin in time and space of the disease. Using whole-genome sequencing of 259 Mycobacterium tuberculosis strains collected from different parts of the world, they determined the genetic pedigree of the deadly bugs. This genome comparison to be published September 1st in the journal Nature Genetics indicates that TB mycobacteria originated at least 70,000 years ago in Africa.

Stunningly close relationship between humans and M. tuberculosis

The researchers compared the genetic evolutionary trees of mycobacteria and humans side-by-side. And to the researcher's surprise, the phylogenetic trees of humans and the TB bacteria showed a very close match. "The evolutionary path of humans and the TB bacteria shows striking similarities," says Sebastien Gagneux.

This strongly points to a close relationship between the two, lasting tens of thousands of years. Humans and TB bacteria not only have emerged in the same region of the world, but have also migrated out of Africa together and expanded all over the globe.

The migratory behaviour of modern humans accompanied with changes in lifestyle has created favourable conditions for an increasingly deadly disease to evolve. "We see that the diversity of tuberculosis bacteria has increased markedly when human populations expanded," says evolutionary biologist Sebastien Gagneux.

Human expansion in the so called Neolithic Demographic Transition (NDT) period combined with new human lifestyles living in larger groups and in village-like structures may have created conditions for the efficient human-to-human transmission of the disease, Gagneux suggests. This may also have increased the virulence of the bacteria over time.

The results indicate further that TB is unlikely to have jumped from domesticated animals to humans, as seen for other infectious diseases. "Simply, because Mycobacteria tuberculosis emerged long before humans started to domesticate animals," says Swiss TPH's Sebastien Gagneux.

New strategies to defeat tuberculosis

Tuberculosis remains a global threat. New drugs and vaccines are urgently needed to fight this poverty-related disease. Multidrug-resistance against first-line treatments is a growing threat in many countries. Therefore, the exploration of the evolutionary patterns of TB bacteria may help predicting future patterns of the disease. This may contribute to future drug discovery and to the design of improved strategies for disease control.
-end-


Swiss Tropical and Public Health Institute

Related Bacteria Articles from Brightsurf:

Siblings can also differ from one another in bacteria
A research team from the University of Tübingen and the German Center for Infection Research (DZIF) is investigating how pathogens influence the immune response of their host with genetic variation.

How bacteria fertilize soya
Soya and clover have their very own fertiliser factories in their roots, where bacteria manufacture ammonium, which is crucial for plant growth.

Bacteria might help other bacteria to tolerate antibiotics better
A new paper by the Dynamical Systems Biology lab at UPF shows that the response by bacteria to antibiotics may depend on other species of bacteria they live with, in such a way that some bacteria may make others more tolerant to antibiotics.

Two-faced bacteria
The gut microbiome, which is a collection of numerous beneficial bacteria species, is key to our overall well-being and good health.

Microcensus in bacteria
Bacillus subtilis can determine proportions of different groups within a mixed population.

Right beneath the skin we all have the same bacteria
In the dermis skin layer, the same bacteria are found across age and gender.

Bacteria must be 'stressed out' to divide
Bacterial cell division is controlled by both enzymatic activity and mechanical forces, which work together to control its timing and location, a new study from EPFL finds.

How bees live with bacteria
More than 90 percent of all bee species are not organized in colonies, but fight their way through life alone.

The bacteria building your baby
Australian researchers have laid to rest a longstanding controversy: is the womb sterile?

Hopping bacteria
Scientists have long known that key models of bacterial movement in real-world conditions are flawed.

Read More: Bacteria News and Bacteria Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.