What Learned About The Plague

by Christopher Paul on February 28, 2011

I learned a few things about The Plague today. I learned that Malcolm Casadaban, a University of Chicago professor of genetics and cell biology, died after handling a modified version of The Plague which is normally less deadly than its regular cousin. Why he had a reaction to this normally docile variant can be blamed on his ancestry.

Turns out, Casadaban had his own weakness—a genetic mutation, common in people of European descent. In fact, this particular mutation is common because it protects against naturally acquired strains of the Plague. If your ancestors lived through a Plague outbreak, you’re more likely to carry it. But, the same mutation also seems to leave you particularly susceptible to weakened, laboratory Plague bacteria.

Casadaban had hemochromatosis which causes a build up of iron. The Plague needs iron to live but the modified version removed the genetic code the bacteria needs in order to steal it from its host. Because of his condition, however, there was so much iron in his system, the bacteria was able to thrive even without the protein.

I never knew the bacteria that caused The Plague needed iron to survive. In fact, I didn’t know much about the disease other than it being attributed to killing roughly half of Europe’s population in the mid 1300’s until I read the Wikipedia entry where it talks about why fleas were so active when infected with The Plague.

The mechanism by which Y. pestis was transmitted was established over the next decade and was found to involve the bites of fleas whose midguts had become obstructed by replicating Y. pestis several days after feeding on an infected host. This blockage results in starvation and aggressive feeding behaviour by the fleas, which repeatedly attempt to clear their blockage by regurgitation, resulting in thousands of plague bacteria being flushed into the feeding site, infecting the host.

Another thing I didn’t know: the bacteria that caused The Plague originally came from China.

The strange story of a scientist killed by the Plague – Boing Boing

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