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

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