I'm planning an experiment involving imaging cultures of mycoparasitic Trichodermium interacting with various species of host fungi and am thinking of various methods of imaging the interaction zone, either on a gel-covered slide or an agar plate.
From an optical point of view, a gelatin-based medium would actually be a advantageous, having a refractive index of 1.53-1.54, close to that of glass, and hence, would maintain a narrower light path and introduce fewer aberrations, etc. Agar has a refractive index of 1.34, close to that of water, and therefore has problems with associated with change of refractive index from glass to water or tissue and back to glass.
However, I know that there are some down-sides to gelatin as a gelling agent, and there's a reason it was largely abandoned in favor of agar in the late 19th Century, but I'm less clear on why that was the case. What are the considerations and precautions about use of gelatin in culture media?
Thanks!
Peter
Gelatin being a protein is readily degraded by proteases produced by growing bacterial or fungal cultures. Once liquified by proteases all microbial colonies will mix up. Thus it's better to use agar or if you intend to have a relatively transparent growth medium you may think of using agarose at 1.5% concentration.
As Shamsher points out, proteases common to many fungi iwill compromise the physical structure of gelatin matrix. You'll also find the gelatin gel matrix pretty soft and increasingly so at even moderately increased temperature.
Btw - could you provide more information re. genus "Trichodermium" or did you mean Trichoderma?
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