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Archive - Aug 30, 2011

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Black Death Pathogen Likely Extinct

The so-called "Black Death," a plague that ravaged Europe between the years of 1347 and 1351, was likely caused by a now-extinct version of the Yersinia pestis bacterium, according to results of a study published online on August 29, 2011 in PNAS. Dr. Hendrik Poinar, from McMaster University in Canada, and colleagues made this determination after analyzing the DNA of 109 human skeletal remains excavated at the East Smithfield mass burial site in London, England. The researchers also studied DNA from the remains of 10 humans unearthed at St. Nicholas Shambles, a site pre-dating the Black Death medieval plague. Individuals buried at East Smithfield harbored Y. pestis genes, which the authors sequenced to form among the oldest and longest genetic assemblages from an ancient pathogen. The genetic sequence differs from the sequences of other known versions of Y. pestis, the authors found, suggesting that the pathogen responsible for the Black Death is likely extinct. Because modern plague continues to affect an estimated 2,000 people per year worldwide, the authors suggest that earlier forms of the disease may yield clues about the pathogen's evolutionary history and possibly reveal how it caused such widespread devastation during the Black Death period. [Press release] [PNAS abstract]

First Kangaroo Genome Sequence Determined

Kangaroos form an important niche in the tree of life, but until now their DNA had never been sequenced. In an article published August 19, 2011 in BioMed Central's open access journal Genome Biology, an international consortium of researchers present the first kangaroo genome sequence – that of the tammar wallaby species – and find hidden in their data the gene that may well be responsible for the kangaroo's characteristic hop. "The tammar wallaby sequencing project has provided us with many possibilities for understanding how marsupials are so different to us," says Professor Marilyn Renfree of The University of Melbourne. Dr. Renfree was one of the lead researchers on the project, which was conducted by an international consortium of scientists from Australia, USA, Japan, England, and Germany. Tammar wallabies have many intriguing biological characteristics. For example, the 12-month gestation includes an 11-month period of suspended animation in the womb. At birth, the young weigh only half a gram, and spend 9 months in the mother's pouch, where the newborn babies reside for protection. Researchers hope that the genome sequence will offer clues as to how tammar wallaby genes regulate these fascinating features of kangaroo life. In addition to zeroing in on the "hop" genes, other exciting discoveries from the genome include the 1,500 smell detector genes responsible for the tammar wallaby's excellent sense of smell, and genes that make antibiotics in the mother's milk in order to protect kangaroo newborns from E. coli and other harmful bacteria. As Dr. Renfree explains, lessons to be learned from the tammar wallaby genome "may well be helpful in producing future treatments for human disease." The first kangaroo genome is a key milestone in the study of mammalian evolution.