By first extracting the DNA of the entire stomach contents from the body of the famous 5,300-year-old ice mummy, researchers have succeeded in isolating the oldest complete genome sequence of a pathogen yet, revealing the Oetzi carried the bacterium Helicobacter pylori.
     Roughly half of all modern humans carry the stomach bacterium, which causes ulcers in a small percentage of carriers and can lead to stomach cancer. In 2010, after completely sequencing the mummy's genome, a team led by archaeologist Albert Zink at the Institute for Mummies and the Iceman in Bolzano, Italy, decided to look for it.
     The strain found in Oetzi is genetically distinct from that most commonly found in modern Europe, which is a hybrid of two strains related to those that circulate in Central and South Asia, and North Africa. Oetzi's matches only the Asian strain. Until now, it had been assumed that Neolithic humans were already carrying the European hybrid by the time they took up agriculture. Oetzi proves this was not the case, suggesting the history of human settlements in Europe is much more complex than previously assumed.
     Humans acquire the bacteria through close contact, and researchers have used the bacterium's DNA to trace past human migrations. Zink's team suggests that the migration which brought the North African strain to Europe occurred after Oetzi died.
     Study co-author Yoshan Moodley says the Oetzi bacterium was probably the original strain that lived in the stomachs of the first Europeans.
     "This ancient HP strain has allowed us what is perhaps a unique opportunity to discover what populations of Helicobacter pylori existed in Europe during this copper age," Moodley reveals. "This might never happen again that we find such a wonderfully preserved specimen where Helicobacter pylori DNA still can be extracted."
     A previous study proposed that it may have arisen in the Middle East as long ago as 50,000 years. Several research projects to take place in South America and Asia are currently at the planning stage.

Edited from EurekAlert!, Nature (7 January 2016)