Now, thanks to a new analysis of dozens of tuberculosis genomes gathered from around the world, scientists are getting a more detailed picture of why TB is so prevalent and how it evolves to resist countermeasures. Writing today (Aug. 21, 2013) in the journal Public Library of Science (PLoS) Pathogens, a team led by University of Wisconsin-Madison researcher Caitlin Pepperell describes a bacterium that marches in lockstep with human population growth and history, evolving to take advantage of the most crowded and wretched human conditions.
"It's as though the bacterium places bets on human behavior," says Pepperell, formerly of Stanford University, and now a professor of medicine and medical microbiology at UW-Madison. "It always bets that humans will go to war, send people to refugee camps, and gather in miserable places. Historically, that's been a winning bet on the bacterium's part."
The PLoS Pathogens study, whose senior author is Marcus Feldman of Stanford, reveals that tuberculosis experienced a 25-fold expansion worldwide in the 17th century, a time when human populations underwent explosive growth and European exploration of Africa, the Americas, Asia and Oceania was at its peak.
"The timing is coincident with expansion, urbanization and colonial migrations of global human populations," Pepperell explains. "These findings suggest that much of the current TB pandemic has its origins in historical events of the last three centuries."
TB is only transmitted by people, and the organism cannot survive in the environment. It thrives, however, in the crowded conditions of prisons, refugee camps and slums, and TB populations tend to be dominated by the bacteria "lucky" enough to land in those environments.
The analysis conducted by Pepperell and her colleagues focused on the role of natural selection, looking at patterns of genetic diversity among 63 TB and related pathogenic mycobacterial genomes gathered from around the globe.
The study shows a highly constrained bacterial genome, with most deleterious mutations quickly discarded. This was especially true for genes essential for causing disease, protein translation and the trafficking and metabolism of inorganic ions, which help control the interaction between the TB pathogen and its human host.
The bacterium's "defense" genes, on the other hand, showed a high degree of tolerance for beneficial mutations, which may play a role in evolution of drug resistance and evasion of the human immune system.
Pepperell notes: "Evolutionary theory predicts that Mycobacterium tuberculosis populations should be vulnerable to extinction. Yet it is obviously highly prevalent. It must have some incredibly clever strategies and tricks to hang on."
As a result, the explosive spread of TB parallels the growth of human populations and takes every advantage of a world where most people live in crowded and impoverished conditions.
The study, according to Pepperell, should help other researchers home in on genes that may be good candidates for targeting with new drugs, and aid disease control strategies that accommodate or even co-opt the bacterium's evolution and help drive its extinction.
In addition to Pepperell and Feldman, co-authors of the new study include Amanda Casto, Julie Granka and Omar Cornejo of Stanford; Andrew Kitchen of the University of Iowa; Eddie Holmes of the University of Sydney; and Bruce Birren and James Galagan of the Broad Institute.
—Terry Devitt, 608-262-8282, firstname.lastname@example.org
Caitlin Pepperell | EurekAlert!
Cystic fibrosis alters the structure of mucus in airways
29.06.2017 | University of Iowa Health Care
Mice provide insight into genetics of autism spectrum disorders
28.06.2017 | University of California - Davis
Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.
Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
29.06.2017 | Physics and Astronomy
29.06.2017 | Life Sciences
29.06.2017 | Health and Medicine