Our distant past has revealed clues to that bad feeling in your gut
- Study led by researchers from China and Norway has uncovered evolutionary history of a notorious, widespread stomach bacteria
- H. pylori hitched rides with humans as they migrated from Africa, and now infects more than half the world’s population
New research has shed light on the mysterious past of a common bacteria that infects more than half the world’s population, and suggests how it became so pervasive.
In a study published in the peer-reviewed journal Nature Communications on November 11, researchers revealed that the bacteria spread out of Africa in at least three waves as it followed ancient human migration patterns.
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To reveal more secrets of the bacteria, Falush and his colleagues assembled a collection of H. pylori strains from Europe, the Middle East, Africa and Asia. Their analysis led them to conclude that the bacteria spread from Africa in at least three separate human migrations.
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The researchers also found clues to each migration. For example, bacteria that were studied from Europe and Asia were different enough from samples in Africa to indicate the first migration wave.
Moreover, the European bacteria was genetically similar enough to bacteria in Sudan in North Africa to indicate another migration event.
“There’s a migration event which basically has left an imprint on all strains in Europe and the Middle East. That’s kind of the base migration and common to all bacteria,” Falush said.
In addition, the authors discovered that bacteria in western Europe had genetic similarities to bacteria currently found in West Africa, due to another independent migration, according to Falush.
“But that isn’t seen throughout the continent. It’s very much concentrated within Spain, Portugal and nearby, and that’s a more recent event.”
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“Deleterious mutations arise all the time in all of the populations, but the reason that our genomes don’t get worse and worse over time is because of natural selection,” Falush said.
“So basically, all of the bacteria in Asia, they all have this kind of long-term effect of bottleneck that they have many mistakes that never get repaired. And this is we claim what allowed the African bacteria to invade.”
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Falush added that the researchers studied deleterious mutations to understand the circumstances that lead genomes to deteriorate.
“Deleterious mutations are important because … without natural selection, the genome of humans will deteriorate over time.
“We for the first time found this can happen in bacteria so that we can use it as a model system by understanding how deleterious mutations accumulate in the population.”
