Ancient Pathogen Genomics: The Genome of the Black Death

Synopsis and Review of Archaeology

Johannes Krause, a professor from the Eberhard-Karls University Tubingen, Germany presented their research on the ancient pathogen Yersinia Pestis bacterium, which was responsibble for the Black Plague, one of the most devastating epedimics in human history. The lecture started off with the history of infectious diseases. He mentioned Zoonosis, or the transfer of pathogens from animals to humans. During the Neolithic Period, humans started to settle down, develop agriculture and domesticate animals; this is where Zoonosis comes in. Their team was able to sequence the entire genome of the Black Death. They were able to reconstruct the genome of Yersinia Pestis allowing them to track the changes in the pathogen’s evolution over time. According to Krause, they got the DNA sequences from the skeletons from East Smithfiels Cementery in London. This cementery opened up during the black death to accommodate more dead bodies. The DNAs they got were subjected to a DNA capture array to fish out the ancient pathogen that they need from the other DNAs (plant, bacteria and fungi). Next they had to test whether the DNAs that they got were 600 years old through the DNA damage profile. The older the sample, the greater the damage it acquires. Finally, the reconstructed DNA sequence were compared to the new strains found as of today and they were able to conclude that Y. Pestis was just one of the causative agents of Black Death, most of the strains today go back to the ancient pathogen therefore there is really nothing special about the ancient strain as compared to the modern strains and finally, that Y. Pestis is the most recent common ancestor (MRCA) of all the modern plagues within the last 4000 years.

The archaeology of this research is very significant and important. The research was done to understand better the evolution of pathogens because of the alarming re-emergance of a new wave of infectious diseases such as HIV, SARS, Hanta, Ebola, Lyme disease and antobiotic resistant paathogens like the Multi-drug-resistant tuberculosis (MDR-TB). These are the new age of epedimics. As stated earlier, most infectious diseases started because of Zoonosis during the Neolithic Period wherein humans started domesticating animals. Some of the major Pandemics in History are the Plague of Athens (4th century BC), the Antonine plague (2nd century AD), the Justinian plague (6th century AD) and the Black Death (14th cebtury AD). First, they had to go back to the bubonic plague cycle to understand how humans were infected and how it spread out across the globe. It was said that the pathogens came from rodents and the fleas were responsible for the transfer of the pathogens to humans. They have concluded that every outbreak today stems from a descendant of the medieval plague. The direct descendants of the same bubonic plague continue to exist today, killing people each year. So,

why is the mortality higher during the medieval period when there is not much of a difference from the ancient pathogens and the modern pathogens? Some of the reasons formulated was climate, next is the change in vector population and con-current disease. It could also be due to human factors. The survivors of that bubonic plague might have carried with him immune genes and passed it through to the next generations. Next, antibacterial medicine have already been discovered to stop these infectious diseases. Also, Humans today have already learned how to adapt to these kind of situations. An example of this is the quarantine which is used to separate and restrict movement of people especially those infected with communicable diseases. Before, ancient people were not aware which was the reason why the pneumonic plague (the transfer of pathogen from human to human through inhalation) happened. This research is very significant to the understanding of the human past specifically the diseases that caused millions of deaths, also to understand the evolution of these diseases and how humans coped up with it through time. This is all done to prevent and prepare for the alarming re-emergence of modern pathogens or the new age of pandemics.