The Black Death

K N and P J Harris ecoli at cix.compulink.co.uk
Sat Nov 16 06:04:49 EST 1996


> ==========
> bionet/microbiology #4284, from sb34 at york.ac.uk, 2136 chars, 10 Nov 
1996 06:35:23 -0
> ----------
> Article: 5285 of bionet.microbiology
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> From: sb34 at york.ac.uk (Sidsel Barfoed)
> Newsgroups: bionet.microbiology
> Subject: The Black Death
> Date: 10 Nov 1996 06:35:23 -0800
> Organization: BIOSCI International Newsgroups for Molecular Biology
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> 
>    I have taken the liberty of subscribing to your list even though I 
am not a microbiologist. 
> 
>    My name is Sidsel Barfoed, I am a postgraduate student at the 
Department of History, the University 
> of York, Great Britain. I am writing a dissertation on the Black Death 
in England 1348-50 seen from an
> epidemiogical point of view.
>   Too many historians use epidemiological data from the turn of the 
century, and I would like to bring 
> the subject a bit more up to date.
>   I allow myself to ask you the following questions:
> 
> 1. Can mutations of Yersinia Pestis take place spontaneously in the 
wild? If so, how long would it take 
> for a mutation to establish itself? I am referring to the following 
articles:
> - R. Rosquist et al., "Increased Virulence of Yersinia 
pseudotuberculosis by two independent 
> Mutations" (Nature, 1988, 11. August, pp. 522-525)
> - B. J. Hinnebusch et al., "Role of the Yersinia pestis Hemin Storage 
(hms) Locus in the Transmission
> of plague by Fleas" (Science, 1996, vol. 273, 19 July,pp. 367-370)
> 
> 2. According to R. Rosquist et al. Y. pestis has mutated at some point 
of time, thereby increasing its 
> virulence. Is there any way of determining when this mutation took 
place?
> 
> 3. Is Y. pestis a "good" or "bad" parasite? I am referring to the 
article by R. M. Anderson and
> R. M. May, "Coevolution of Hosts and Parasites" (Parasitology, 1982, 
vol. 85, pp. 411-426)
> 
> 
> I hope you will be able to answer my questions. Should you find my 
subscribtion unsuitable, I will 
> withdraw it immediately.
> 
> Yours sincerely
> 
> Sidsel Barfoed
> sb34 at york.ac.uk
> 
> 
> 
Black Death and mutations. The answer to your first question is that 
mutations can certainly take place as long as the organism is capable of 
growth. A very rough rule of thumb is that a mutation is likely (on a 
very broad average) about every 10000 cell dividions.(I await correction 
from geneticists with more up-to date information).
However, the vast majority of these mutations will be lethal, the mutant 
cell will simply die because something is now wrong with it. Some 
mutations will be so trivial that they have no significant effect on the 
organism. Some may result in a viable mutant that is not as competitive 
as the parent strain.So the chance of a successful, competitive AND more 
virulent strain resulting from mutation is very, very small but, most 
importantly, not nill. Since microbial populations are counted in 
millions, the number of potential mutations starts to look more 
interesting.
I regret that for your other questions I cannot offer answers.
Peter Harris
Reading Univ, Department of Soil Science.
AKA <P.J.Harris at reading.ac.uk>




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