[Drosophila] Re: initial population and inserts

Mark Thorson via dros%40net.bio.net (by nospam from sonic.net)
Wed Sep 12 16:29:46 EST 2012

Laurence Mueller wrote:
> Mark,
> I guess I am not sure exactly what you are trying to do. On the one hand you
> ask if you should select the first emerging flies so you can apply selection
> for rapid development. But then you state that your lines are inbred. If you
> have an interest in selecting for rapid development than inbred lines are,
> of course, the worst material to work with. You should be using genetically
> variable populations (not Oregon R) that have preferably adapted to the
> "lab" environment.

I'm stuck with the line I'm using, so I won't be changing.
I have been assuming there would be little genetic variability
in this line.

> Your earlier posts seem to deal with problems of bacterial growth and issues
> about the composition of the fly medium. The larvae actually do best on
> medium with active yeast populations (see references by Sang and others in
> my publication #13). Most recipes for fly food I am familiar with put some
> sort of acid in the fly food (e.g. propionic acid) which inhibits molds and
> bacteria but is conducive to yeast growth. In the end I would suggest using
> a fly food recipe others have used rather than re-inventing the wheel.

I am using cream of tartar.  It seems as though there's
an optimal range -- using too little promotes bacterial
overgrowth but so does using too much, presumably because
at high concentration it's retarding the yeast and
favoring acid-tolerant bacteria.

I would use a standard recipe, except that I don't want
to use mold inhibitor or an autoclave.  My application
doesn't allow methyl paraben, and the additional time
for cooking would be a big burden.  The recipes I've
looked at use methyl paraben, autoclaving, and then
inoculate with yeast after cooking.  I have used a recipe
that had thymol as the mold inhibitor, which would be
acceptable, but I don't have a source for pure thymol
and it requires high-proof alcohol as a solvent which
is hard to get here.

> I'm sorry to hear my PNAS and Science articles were not useful. You may want
> to look at publication #13 which reviews the lab ecology of Drosophila.

Thanks, I'll look at that too.

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