Mike Dalbey dalbey at biology.ucsc.edu
Fri Jan 19 13:11:41 EST 2001


I believe that the information provided by alonnardi at yahoo in response to your
question is partly incorrect. After all, someone offering to answer questions
in so many fields of knowledge ( "biology, microbiology, chemistry,
biochemistry etc." ) can hardly be expected to have professional expertise in
them all.

They have given you an acceptable definition of AUXOTROPHIC (though I think the
term may have been first used to describe mutants of the fungus Neurospora, and
is therefore not restricted to prokaryotes).

However, AUXOTROPHIC is NOT the opposite of AUTOTROPHIC. The opposite of
AUXOTROPHIC is PROTOTROPHIC (the property of having a complete set of
biosynthetic pathways, so that the organism requires only a single, simple
carbon-based molecule).

AUTOTROPHIC means that most carbon for biosynthesis is derived specifically
from CO2 or bicarbonate ion in solution. Biochemically, autotrophy is based on
a pathway called the Calvin Cyle (in plants). AUTOTROPHIC is the opposite of

It is probably true that many or most autotrophs are prototrophs, but not
nearly all prototrophs are autotrophs.

Wild-type strains of E. coli are prototrophic, but auxotrophic strains are
easily obtained in ther laboratory. Both the wild-type and the mutants are
herterotrophic, not autotrophic.

More than a normal daily dose of jargon, I'm afraid.

Mike Dalbey
dalbey at biology.ucsc.edu

> Hi Gavin!
> The term auxotrophic relates to prokaryotic organisms that cannot produce
> essential compounds for their "living" (such as germs that cannot produce
> the amino acid metionen) in comparison to the wild type of that particular
> type of germ.
> The term autotrophic means the opposite of auxotrophic and relates to
> prokaryotic organisms that can produce essential compounds for their
> "living", another words, the term autotrophic refers to the wild type of a
> prokaryotic organism.
> I will be happy to answer any of your other questions in biology,
> microbiology, chemistry, biochemistry etc. at my email: alonnardi at yahoo.com
> "Gavin" <gavin at zonvark.wustl.edu> wrote in message
> news:39EF2F13.83985F53 at zonvark.wustl.edu...
> > Hi,
> >
> > Just a quick question:  What does "auxotrophic" mean?
> > I suspect it is not the same as "autotrophic".
> >
> > Gavin
> >
> >

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