In article <ECS9611101443A at york.ac.uk>
sb34 at york.ac.uk (Sidsel Barfoed) writes:
> 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)
>
It certainly is possible for mutations to occur in the wild. That is
why new virulent strains of bacteria and viruses occasionally appear.
As to the second part of your question, I think it would be pretty hard
to determine how long it would take to be established in the
population. This really takes into account the rate of spread of a
disesase.
Certainly new strains of flu can get established in a few years around
the world. There is no reason bacteria should be very different. For a
highly virulent and easy to spread organism, it should be quite rapid.
I think the limiting factor is movement of people from area to area.
> 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?
>
It might be possible, but it would take a lot of work. One would need
to get sammples of Y. pestis DNA from differing periods of time that
bracketed the time of interest. One could design PCR primers to
identify whether a specific mutation has taken place. I don't know
whether you could still find DNA from these bacteria after a thousand
years or not.
> 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>
Michael Benedik
Department of Biochemical Sciences
University of Houston
benedik at uh.edu
