Carl Zimmer in his blog, The Loom:
The discovery of H. pylori’s role in ulcers attracted a huge amount of attention to the bug, and to its effects on different people. In the late 1990s Mark Achtman, a German microbiologist at the Max Planck Institut for Infectious Biology, began to gather strains of H. pylori from around the world. He and his colleagues compared the DNA from the strains to see how they were related to one another. They found something strange. Most of the H. pylori strains they collected in China and Japan appeared to be closely related to one another. Based on the diversity of these Asian germs, Achtman suggested they had arrived in the stomachs of early Homo sapiens that moved into Asia some 40,000 years ago.
Further research by Achtman and others indicated that other ethnic groups also carried their own strains of H. pylori. A debate then emerged about how germ and host got associated in this way. H. pylori is not like the flu, which can move between continents in a matter of days. Scientists don’t know much about how it gets from stomach to stomach, but it seems to move mostly within families. So it would make sense that H. pylori’s genealogy tracked the genealogy of its hosts. On the other hand, some critics have argued, H. pylori might be a recent arrival in our stomachs. If it jumped from animals to humans on several occasions in different parts of the world, it might have produced the same patterns seen by Achtman and others.
In this week’s Nature, Achtman and his colleagues report the latest data on humans and their ulcer bugs. They argue that our histories are even more intimately wrapped together than previously thought…