Black Death Code Cracked
October 13, 2011 by staff
The work opens the door to the possibility that science can now trace the secular evolution of a bacterium that was one of the worst murderers of all time, but now is relegated to the pockets of activity in the developing world. The scientists said that modern strains of bacteria are all descended from a variant of the Black Death.
An estimated 50 million people died during the reign of five years of the Black Death of terror in Europe in the mid-14th century. Today, the bacteria believed to have caused the outbreak – Yersinia pestis or plague – claims about 2,000 lives a year in parts of Africa, India and China.
The complete sequence of Yersinia former was prepared from DNA fragments recovered from human teeth found in a mass grave for victims of the Black Death in East London, near the site of the Tower of London.
The project was led by Hendrik Poinar, director of the Center for Ancient DNA at McMaster University in Hamilton, and Johannes Krause of the University of Tübingen in Germany. The report on his work was published Wednesday in the journal Nature.
It was hailed as an impressive piece of science.
“It’s great,” said Dr. Jeffery Taubenberger, the American scientist who led the effort to find and sequence the virus that caused the Spanish flu pandemic of 1918, the only previous time was an old pathogen decoded.
Have moved from small DNA fragments in the complete genome is “a remarkable technical achievement,” said Taubenberger, who heads a laboratory at the U.S. National Institute of Allergy and Infectious Diseases in Bethesda, Maryland
This group of scientists reported in late summer they had found small fragments of DNA from Yersinia. That represents 0.002 percent of the genome, said Krause, whereas now 99 percent of the genetic code of the bacterium has been sequenced.
Poinar accredited rapid technological advances to make the work possible.
“Even a year ago was almost a dream to get this level of genomic information,” he said in a telephone interview.
There has been a long debate in scientific circles as what caused the Black Death of 1347-1351, with most bets riding on the plague. However, some scientists argued that a viral hemorrhagic fever is more likely to blame, pointing to the fact that no contemporary plague kill with the speed and spread of the Black Death.
“It was a sort of plague – no pun intended – people for many, many years in terms of epidemiological patterns differ from pests today,” said Poinar, who said that this work puts more weight theory behind the plague.
Poinar team is still working with the material collected from the teeth to see if they can identify other disease agents that could have infected the victims at the time of death.
He and his colleagues speculate that the Black Death cut a deadly swath because it may have been the first time that the pathogen was transferred to the human population, that is, no one had antibodies to protect against it.
In addition, weather conditions were perfect for the spread of disease. Households and communities are full of people, no sanitation, people were undernourished and as antibiotics and antiviral drugs had not yet been discovered, infections can not be treated.
“That goes back to the notion that it was in 1348 – wet and foggy, mashed London, where people were co-infected, probably with a million other insects,” Poinar said. “We have fantastic laboratory and antibiotics.”
Poinar said that an expert in antibiotics has studied the genome and believes that drugs used to treat plague cases present day would be effective against the variety century 14.
While Krause Poinar and argue that their findings help make the case that the Black Death was the plague, suggesting that the work casts doubt on the assertion that a previous outbreak, the Plague of Justinian in the sixth century, was also caused by the plague.
Theanlysis of the virus genome suggests that the plague began to infect humans for the first time between 1200 and 1340, Krause said.
The DNA was recovered from the teeth of the jaws are four different pit in East Smithfield, a mass grave dug in late 1348 or early 1349 for, among the bodies of people killed by the Black Death .
Two individuals were adult females and one was a minor whose gender can not be determined. Scientists can not estimate the gender or age of the fourth.
The researchers were able to extract DNA fragments from the pulp of the teeth. Using sequences of genetic today as a template Yersinia pestis bacteria were able to assemble the 14 century version of the plague.
The differences between bacteria of the day and the resurrected bacteria are not huge, it is not immediately apparent what caused the previous version a mass murderer. Poinar notes, however, are not sure what the correct order of genes is. Thinking that may help explain why the ancient bacteria was so virulent.
In addition, there are small differences in the bacteria that can give clues, he said. “We do not think necessarily a smoking gun. (But) there are a handful of substitutions that are very interesting that is worth following up.”
His group is collaborating with scientists in New York to try to focus on the importance of genetic changes.
Working in high biosafety laboratories, scientists are looking to see if changing the code of modern days Yersinia strains to include substitutions would ramp up the virulence of the bacteria. They are doing the work in the testing of chemicals, not animals.
As required by the rules of scientific publishing, Poinar’s team will put the sequence of the bacterium Yersinia old in GenBank, a database of open access.
He recognizes that it is likely to cause alarm in some quarters.
“I think it has some people nervous,” he said. “(But) the science has to move forward and we need to know if these are the changes and these changes may account for the increased virulence and we control for the virulence of today.”
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