"Roy" > wrote in message
oups.com...
> >Which also makes me think that yes this culture does contain *some*
> commercial yeast
>>
> Be reminded that yeast classification is ever evolving and that
> confuses layman and even scientific professionals in other fields who
> want to get a consistent classification in this particular microbe when
> they encounter this in their research work.

Roy: have you seen the following article?
Graham

Nature 434, 636 - 640 (31 March 2005); doi:10.1038/nature03405



Sex increases the efficacy of natural selection in experimental yeast
populations

MATTHEW R. GODDARD*, H. CHARLES J. GODFRAY & AUSTIN BURT

NERC Centre for Population Biology and Department of Biological
Sciences, Imperial College London, Silwood Park Campus, Ascot SL5 7PY,
UK
* Present address: School of Biological Sciences, The University of
Auckland, Private Bag 92019, Auckland, New Zealand


Why sex evolved and persists is a problem for evolutionary biology,
because sex disrupts favourable gene combinations and requires an
expenditure of time and energy. Further, in organisms with
unequal-sized gametes, the female transmits her genes at only half the
rate of an asexual equivalent (the twofold cost of sex). Many modern
theories that provide an explanation for the advantage of sex
incorporate an idea originally proposed by Weismann more than 100 years
ago: sex allows natural selection to proceed more effectively because
it increases genetic variation. Here we test this hypothesis, which
still lacks robust empirical support, with the use of experiments on
yeast populations. Capitalizing on recent advances in the molecular
biology of recombination in yeast, we produced by genetic manipulation
strains that differed only in their capacity for sexual reproduction.
We show that, as predicted by the theory, sex increases the rate of
adaptation to a new harsh environment but has no measurable effect on
fitness in a new benign environment where there is little selection.

http://www.nature.com/cgi-taf/DynaPa...e03405_fs.html