Bob bbruner at
Fri Oct 27 19:42:35 EST 2000

On Wed, 25 Oct 2000 10:11:45 +0200, Rafael Maldonado
<rmaldonado at> wrote:

>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. 

Hm, that led me to actually look up some definitions.

King and Stansfield, Dictionary of Genetics (4/e). A mutant
microorganism that can be grown only upon minimal medium that has been
supplemented with growth factors not required by wild-type strains.

Brock Biology of Microorganisms (9/e). An organism that has developed
a mutational requirement through mutation.

So both of those would tend to agree with you. However, since all
(modern)  nutritional requirements originally arose by mutation  (in
one organism or another), the distinction is not all that clear. In
common usage, the term is most often used to refer to mutants from a
particular parental (reference or wild type) strain. However, the
broader usage is also seen. After all, wild type itself is rather

>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.

The problem with that definition is that it requires external
knowledge to apply it. When the Martians come, and find that the first
10 earth-humans they meet require Vit C, they will be unable to say,
one way or the other, whether they are Vit-C auxotrophs because they
do not know the "wild type". That is an awkward constraint on a term!


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