Genome from mass grave shows the Black Death introduced the world to the plague

[DainBramaged]

In August, researchers provided definitive evidence that Yersinia pestis, which is still causing infections in humans, was the bacteria behind the Black Death, perhaps the most deadly disease outbreak in human history. They managed this by unearthing skeletons from a mass burial site in London and obtaining DNA sequences from the bacteria that killed those interred over 500 years ago. Now, some of the same people are back with a new publication in which they report a draft of the entire genome sequence of the bacteria behind the Black Death.

The new genome is not complete, but it clearly shows that the bacteria found in England are nearly identical to an ancestral species that did not infect humans, and shares common features with all modern strains. The authors conclude that the medieval plague almost certainly introduced Y. pestis to the world, and that some factor other than the bacteria themselves may have been the key to making the plague so deadly.

Their earlier work on samples from the grave site had allowed the authors to identify samples that had preserved relatively high amounts of DNA. To separate out the Y. pestis DNA, they constructed a DNA chip that contains sequences from the modern bacteria; the DNA from the plague bacteria base-paired with the DNA on the chip, allowing it to be separated out from all the other bacterial and human DNA present in the samples. This technique would miss any large insertions or deletions of DNA, but is enough to provide a good draft of the genome (which can allow follow up work to fill in any gaps).

With the DNA they isolated, the authors were able to put over 4.3 million bases (Megabases) into continuous stretches of DNA; only 10 areas showed signs of major rearrangements. Overall, the authors obtained sequence for 93 percent of the genome areas they targeted with their DNA chip. In all those millions of bases, there were only 97 differences between the plague bacteria and a modern strain. Each one of these differences was present in an ancestor, Y. pseudotuberculosis, that does not infect humans. Thus, the plague bacteria is at or very close to the root of the Y. pestis phylogenetic tree.

http://arstechnica.com/science/news/2011/10/genome-from-mass-grave-shows-the-black-death-introduced-the-world-to-the-plague.ars

[formercia]

1. It was the lack of Cats

Someone in the 'Church' Hierarchy equated cats with Satan. There was a massive campaign that nearly exterminated Cats from Europe, allowing the Black Rat to flourish. The Rats carried the fleas that carried the Black Death, and the Rats acted as a reservoir for the Plague.
It was just a simple case of more Vectors in close contact with the population.

[bluedave]

2. Aw

it was the lack of rat eaters,including people

[formercia]

3. There are people in India who eat Rats

Whole families are engaged in the sport. They catch and eat Wood Rats that eat Rice in the fields and burrow in the Paddy Dikes.
The Wood Rat is just like any other creature in the Woods, not dirty or infected with Plague.
The farmers benefit and the Rat catchers get needed Protein.

[msanthrope]

4. Well, I can attest to the fact that my three bastards keep my historical pile picked clean.

When my neighbor had a problem, the kitties visited her cellar overnight. No more problem.

[Aerows]

5. Exactly

That's why the rats flourished - because someone decided that cats were evil. Chalk this one up to yet another religious zealot who brought sorrow to humanity.