From: Michael M. Butler (butler@comp-lib.org)
Date: Wed Oct 03 2001 - 21:32:24 MDT
Hoo boy. Not sure where this is from, but interesting if true.
Bubonic plague genome is "unusually fluid"
19:00 03 October 01
Debora MacKenzie
Bubonic plague, the bacterium blamed for the Black Death of medieval
Europe and now a potential biological weapon, has had its entire
genome sequenced. The genes seem to be "unusually fluid", readily
re-arranging themselves and picking up new genes from other microbes.
That could mean that more virulent strains of plague might emerge.
More ominously, it suggests that enhanced strains might be relatively
easy to develop as weapons.
The bacillus that causes bubonic plague, Yersinia pestis, commonly
infects rodents in Asia, Africa and the Americas. But it occasionally
spreads to humans, with lethal effect.
It does so by infecting both insects and mammals. Fleas that feed on
infected rodents swallow the bacteria, which infect and block their
midguts. The starving fleas feed voraciously, but only regurgitate
the blood they try to swallow - along with the bacteria. So plague
spreads among rodents, often causing only mild disease.
If the infected flea bites a human, however, up to half the victims
die, unless treated with antibiotics. If the bacteria invade the
lungs of such patients, and they cough them out, nearby people may
catch "pneumonic" plague. This is always fatal without treatment.
Pneumonic plague is the form feared as a potential biological weapon,
as it can be released as an aerosol and can spread directly among
humans, without the intervention of fleas. The Soviet Union developed
such a plague weapon.
"Pathogenicity islands"
The gene sequence of Yersinia pestis, produced by Julian Parkhill of
the Sanger Centre in Cambridge, UK and colleagues, shows how the
bacillus learned to infect both insects and mammals.
It picked up genes directly from baculoviruses that infect insects,
including one for a toxin that damages the midgut. It also acquired
"pathogenicity islands", assemblages of genes from other bacteria
that help cause human disease.
The sequence also reveals novel surface molecules, which might
provide new ways to attack plague. But "this genome displays unusual
fluidity," comment Stewart Cole and Carmen Buchreiser in Nature,
where the genome is published. Numerous Yersinia genes have been
copied backwards and have swapped positions within the genome,
sometimes creating different variants in the same population.
These recombinations could mean differences in virulence in a single
batch of plague, they note. That could also mean that the bacteria -
or bioweapons developers - have the genes at their disposal for new
and potentially nastier strains of disease.
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