In article <[log in to unmask]>, James Fischer
<[log in to unmask]> writes
>Anything that does
>not kill 100% of the spores and "live" bacteria (and nothing short of gamma
>beam or electron beam irradiation will kill them all) will certainly
>result in a
>"surviving strain" developing.  The "survivor strain" survives due to
>some small
>difference between it and the strain(s) that were killed.

I have no wish to get involved in this thread which is getting way off
beam so far as I can see.

However, the above merits some comment as I feel it is inaccurate and
intended to lead the reader into a possibly false conclusion.

Most survivors from treatment regimes are in fact nothing to do with the
scenario you depict. It is usually down to the organism just getting
lucky.

As an example, most varroa mites surviving a routine Apistan application
(given that you are not in a situation where resistance is already
developed) are not resistant. They just happened not to meet the
treatment sufficiently strongly to be killed, or perhaps not even meet
it at all.

Your scenario relies on the assumption that resistance is the only
variable at play and this is simply incorrect. Most cases are down to
inefficiency and inconsistency of the delivery system of the treatment.
Genetic difference is certainly a possibility, but not as you indicate,
a certainty.

Resistance is certainly selected for, but to say that exposure to
treatment gives rise to new strains automatically is a leap too far. The
resistance must already have some genetic basis to be selected for, or
arise by mutation at some time after first exposure. I very much doubt
that resistance mutations are caused by the treatment (which I
appreciate you did not actually say), but that conditions conducive to
the new mutation prospering are created.


--
Murray McGregor