Genetics decoded by pest infestations

Genome of medieval plague bacteria decoded

10/13/2011

Researchers from the University of Tübingen and Canadian colleagues reported back in August that they had identified the plague bacterium responsible for the spread of the deadly disease in Central Europe in the 14th century. Now they are decoding the genome of Yersinia pestis bacteria successful.

For some time now, Yersinia pestis bacteria have been the probable cause of the plague in the Middle Ages. The researchers at the University of Tübingen had already confirmed this suspicion in August as part of a comprehensive investigation. Now they have succeeded in deciphering the genome of the plague bacteria. In this case, the Yersinia pestis bacterium differs only in a few places from the pest-pathogens that are still common today, report Prof. Dr. med. Johannes Krause from the University of Tübingen and colleagues in the current issue of the trade journal „Nature“.

The mother of all pests
According to the researchers, Yersinia was pestis „so to speak, the mother of all today's Pesterreger“ and responsible for that as well „Black Death“ well-known plague epidemic in the 14th century in central Europe, where according to various scientific data between 25 and 50 percent of the European population died. Prof. Dr. Johannes Krause from the University of Tübingen and colleagues have now decoded the bacterial heritage of the pathogens and in the journal „Nature“ presents. The researchers found that the genome of Yersinia pestis bacteria is amazingly similar to the still existing plague bacteria. Only at twelve sites, the genome of the bacteria from the Middle Ages differs from the most widespread next-day plague pathogens. According to the experts, the fact that the plague caused such a fatal epidemic only in the 14th century is due to the fact that the pathogens first appear „neither man nor his immune system to deal with it“ knew. In the course of the plague, however, a large proportion of the people who were particularly susceptible to the pathogens had died and the survivors probably had a more resistant immune system, according to the researchers' explanations for the absence of further plague epidemics. In addition, the population was later better equipped to prevent the spread of the plague through improved hygiene and the introduction of quarantine for patients and so-called plague houses.

The researchers at the University of Tübingen succeeded in finally detecting Yersinia pestis as the trigger of the plague epidemic in the Middle Ages in August after they had genetically analyzed more than 100 skeletons from a London plague cemetery together with Canadian and British colleagues and searched for traces of the pathogens. The sequencing of less than one percent of the genome of the pathogens was sufficient to provide unequivocal evidence, emphasized Prof. Dr. med. Johannes Krause published the results in the US trade journal „Proceedings of the National Academy of Sciences“ (PNAS). Already after the first examinations Krause explained, much points to it, „that at least a part of the genetic information of the pest organisms has hardly changed in the last 600 years“.

Plague in the Middle Ages claimed 25 million lives
The plague epidemic between 1347 and 1353 was the largest epidemic in Europe so far and claimed around 25 million lives. According to previous findings, the infectious disease spread initially in Asia and arrived from here with the rats aboard ships to Europe. Especially in cities such as Cologne, Hamburg or Bremen, the Black Death in Germany ravages with fatal consequences, whereby the pathogens were able to spread quickly due to poor hygiene and the relatively high population density. However, despite the extensive research, it is still not fully understood why the plague spread so rapidly in the 14th century, whereas today's plague pathogens spread much slower even in the absence of hygiene facilities and lack of medical care. According to World Health Organization figures, around 100 to 200 people around the world still die each year from the plague, with up to 3,000 diseases registered each year, with much of the plague occurring in developing countries. With the infection numbers from the Middle Ages, these numbers are not comparable. (Fp)

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Picture credits: Cornelia Menichelli
Image: Atlas of World History, Roger Zenner, Creative Commons by / sa / de