Growth medium coloring

Peter Herman x5495 rpeter at nmsu.edu
Fri Jun 30 15:20:21 EST 1995


In article <DAyAF1.LnB at news.cis.umn.edu> brambl at molbio.cbs.umn.edu (Robert Brambl) writes:
>Chuck Staben's good suggestion probably stems from another useful  
>application of water-based culinary food colorings:  to stain growth  
>media-agar plates and tubes in a genetics laboratory where it is essential  
>to keep separated media of various compositions. These coloring agents are  
>apparently harmless to fungi, or at least to Neurospora. 

For some organisms this is great!  Unfortunately, others are really 
picky and even food coloring can cause problems.  I ran into trouble with 
some Oomycetes (Achlya and Saprolegnia) and blue food coloring.  So, it 
is a good idea to test each color (sometimes the sensitivities are 
different) on a few plates before pouring too many!

>Alternatively, for a really dark effect, use India ink in agar; but use  
>the real stuff, and not New Age substitutes that contain detergents and  
>surfactants.

Perhaps the most dramatic mycological demonstration going is cytoplasmic 
streaming in Physarum grown on Oatmeal Agar with India Ink.  The contrast 
is awsome!  This has been a no fail demo in biology and mycology classes 
for me for years.  One word of advice for those who have never made it, 
Oameal Agar is really viscous and you can blow it over in the autoclave 
unless you leave enough headspace in the flask.  Though it happened 
nearly 30 years ago, I can still remember cleaning up the mess I made 
with 20 L. of the stuff as a 1st year grad student!

Peter


*   Peter Herman, Dept. of Biology	Phone: +1 505 646 4532    *
*   New Mexico State University		Fax:   +1 505 646 5665    *
*   Box 30001, Dept. 3AF					  *
*   Las Cruces, NM 88003 USA		e-mail rpeter at nmsu.edu    *



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