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+ - Lyme bacterium's possible ancestor found in ancient tick->

Submitted by Taco Cowboy
Taco Cowboy (5327) writes "A few ancient ticks, some 15-million to 20-million old, were trapped inside a piece of amber

That piece of amber was bought by a researcher some 25 years ago, in Dominican Republic

Only recently that researcher took a closer look with a powerful compound microscope — magnifying the specimen up to 1,000 times — that he noticed the tiny ticks within

Upon examination, that researcher turns up some ancient bacterium in one of the ticks. The bacterium appears to be spirochetes, a group of rotini-shaped bacteria responsible for many human diseases

Although Lyme disease did not exist back then, the spirochetes in the fossil tick probably contributed to the genetic diversity of the 12 or more species of Borrelia that cause Lyme and similar diseases today, says the researcher

Like modern ticks, the ancient ones likely picked up spirochetes when they took blood meals from infected vertebrates. Which of those hosts served as a natural reservoir for the spirochetes found in the juvenile tick, however, remains unknown. Ancestors of modern-day jaguars, ancient woodpeckers and shrewlike solenodons are a few potential spirochete-harboring hosts that lived in the same hot, balmy forest as the tick. The researcher, however, thinks it is more likely that the tick inherited its spirochetes from its mother (a process called vertical transmission), rather than from an animal reservoir. He found no evidence that the young arachnid had feasted on blood prior to its fatal encounter with the amber-forming tree resin

The researcher placed the newly discovered bacterium within its own genus, naming it Palaeoborrelia dominicana. He could not attempt to analyze the ancient DNA to confirm whether or not the bacterium is related to modern Borrelia because those tests would destroy the specimen. So it is impossible to know how closely — if at all — the ancient spirochetes are related to contemporary Borrelia. But the bacteria’s morphology and its location within the tick’s alimentary tract indicate that it probably has ties to those notorious pathogens

While on a related article on Nature — @ http://www.nature.com/news/lym... — it has been shown that Borrelia burgdorferi, the bacterium that causes Lyme disease, shows that the capacity to evolve can itself be the target of natural selection

The oldest evidence of Lyme disease dates back 5,300 years, to an ice mummy discovered to contain Borrelia’s genetic material, but the condition’s evolutionary origins are unknown. Lyme disease is only one of a number of human afflictions caused by spirochetes, however, so even if that condition arose more recently, our problems with spirochetes likely date back much further. When Homo sapiens arrived on the scene around 200,000 years ago, the researcher thinks, the ticks — and their spirochetes — were probably waiting “As long as humans have been around,” he says, “I’m sure that they suffered from ailments caused by spirochetes carried by ticks”"
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Lyme bacterium's possible ancestor found in ancient tick

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