Gastritis pathogens found in Oetzi the iceman
Helicobacter pylori genome of the glacier mummy decoded
January 07, 2016
Nowadays, the bacterium Helicobacter pylori is present in the stomachs of approximately one-half of the world's population. Under unfavourable conditions, it can cause stomach ulcers and even cancer. An international research team involving researchers from the Max Planck Institute for the Science of Human History has now succeeded in decoding an H. pylori genome from the 5,300-year-old glacier mummy Oetzi. Surprisingly, the comparison with modern H. pylori bacteria showed that the strain in the iceman resembles strains in Asia and not Europe. These findings raise new questions about the early migration of humans to Europe.
Previous studies have shown that Iceman Oetzi lived in southern Europe in the eastern Italian Alps and was one of the early European farmers. Nearly three years ago, researchers at the European Academy in Bolzano began to examine the stomach of the mummy more closely. Together with colleagues in Kiel, Vienna, and Venda, and with researchers at the Max Planck Institute for the Science of Human History in Jena, they extracted genetic material from the 5,300-year-old tissue and enriched it specifically for the DNA of Helicobacter pylori. The research team managed to isolate sufficient ancient genetic material to be able to reconstruct the whole genome of these ancient bacteria.
More detailed investigations of the bacterial genome from the Copper Age revealed that the genome carries features that are highly virulent; nowadays, in humans, these same features can lead to gastritis.. In Oetzi's stomach remains, the researchers also discovered proteins that can be detected in patients suffering from H. pylori infections today. One-tenth of those infected tend to develop stomach problems in later life. "We cannot say for sure whether Oetzi had gastritis or stomach ulcers, since his stomach lining no longer exists, which is where the diseases tend to manifest themselves initially. The conditions for such diseases, however, did exist", notes Albert Zink, a microbiologist in Bolzano, about the famous mummy's stomach.
Variant of bacteria challenges immigration history
Since within families, H. pylori is mostly transmitted to subsequent generations, the pathogen is an ideal marker forr tracking human migration. Previous studies have shown that there are variants which occur particularly frequently in certain parts of the world. However, that the ancient Helicobacter strain can be compared with strains from Europe and Asia that are known today surprised the researchers. "We assumed that the strain of the glacier mummy is similar to the modern European strain, but various analyses yielded the same results – the similarity with the Asian strain is the greatest," explains Alexander Herbig from the Max Planck Institute for the Science of Human History, one of the main authors of the study.
These findings challenge previous assumptions about the various time-points of immigration into Europe. "So far it has been assumed that the Neolithic farmers already carried the European variant when they settled in Europe. Since Oetzi, as an early farmer, however, was a carrier of the Asian variant, there must have been another movement of people to Europe at some point in time after Oetzi - by people who brought today's European variant of the virus with them," says Johannes Krause from the Max Planck Institute, continuing: "The colonization history of Europe is very complex and will continue to surprise us with ever new insights."
So far, however, this study only offers preliminary clues about migration movements in Europe. Further comparisons with ancient remains from Asia and Africa from different periods are required to better understand European migration.