ekhatipo at NOSPAMmidway.uchicago.edu
Mon Oct 30 22:22:27 EST 2000
I don't think that the term auxotroph should (though can) be applied to
complex organisms like H. sapiens. On the other hand, since you've mentioned
cyanobacteria, heterocysts of filamentous cyanobacteria can fix nitrogen,
while other cells from the same filament (about 90%) cannot grow without
nitrogen and would depend on N fixed by heterocysts. Nobody knows "wild
type" of ,e.g, Thiocapsa roseopersicina (purple sulfur bacterium) that would
be able to grow on minimal medium not supplemented with vitamin B12. In case
of Thiocapsa, as well as some other bacteria (wild type), it is just the
property of a species to have nutritional requirements.
Which mutant is a wild-type species having a certain nutritional
So, both terms, auxotrophic and wild type, have a pretty arbitrary
definition. And this is what I meant by saying that an auxotroph is not
always a mutant.
"Rafael Maldonado" <rmaldonado at ua.es> wrote in message
news:39F695C1.3AB6E67E at ua.es...
> Emir Khatipov wrote:
> > It does not have to be a mutant.
> Sorry, I don't agree. An auxotroph is a mutant strain which need a
> nutritional requirement that the wild type does not require. It is the
> only way to detect a auxotrophic requirement. Whitout this premise,
> every living organism is auxotroph (except some cyanobacteria, which can
> live with practicaly air and sunlight)
> For example, Homo sapiens is not a auxotroph of vitamin C, because
> although people need vitamin C for living, the wild type (actually,
> everybody) does need it.
> Auxotrophic organism would just have a
> > requirement in a certain or a number nutrients/factors for growth, e.g.,
> > some photosynthetic bacteria require group B vitamins.
> > Prototroph is an antonym for auxotroph (in case that the auxotrophic
> > phenotype is a result of a known mutation).
> Rafael Maldonado
> Divison of Genetics
> University of Alicante (Spain)
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