About 20 million years ago, a single flea became entombed in amber with tiny bacteria attached to it, providing what researchers believe may be the oldest evidence on Earth of a dreaded and historic killer - an ancient strain of plague. If, indeed, the fossil bacteria are related to plague bacteria, Yersinia pestis, the discovery would show that this scourge, which killed more than half the population of Europe in the 14th century, actually had been around for millions of years before that, traveled around much of the world, and predates the human race. Findings on this extraordinary amber fossil were published online on September 15, 2015 in an open-access article in the Journal of Medical Entomology by Dr. George Poinar, Jr., an entomology researcher in the College of Science at Oregon State University, and a leading expert on plant and animal life forms found preserved in this semi-precious stone. The article is titled “A New Genus of Fleas with Associated Microorganisms in Dominican Amber.” It cannot be determined with certainty that these bacteria, which were attached to the flea's proboscis in a dried droplet and compacted in its rectum, are related to Yersinia pestis, scientists say. But their size, shape and characteristics are consistent with modern forms of those bacteria. They are coccobacillus bacteria; they are seen in both rod and nearly spherical shapes; and are similar to the shapes of Yersinia pestis. Of the pathogenic bacteria transmitted by fleas today, only Yersinia has such shapes. "Aside from physical characteristics of the fossil bacteria that are similar to plague bacteria, their location in the rectum of the flea is known to occur in modern plague bacteria," Dr. Poinar said.
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