Other uses for microscope?

[FLJohnson]

Having a high quality microscope is certainly useful for monitoring the quality of yeast in culture. Besides looking for obvious bacterial contaminants and performing yeast cell counts, what do microbiologists use the microscope for in a yeast lab? How can we as homebrewers use our microscopes beyond cell counting? Are there morphological changes in cells that would indicate mutations or undesirable changes in the culture? What are the pros looking for?

 

[Sourz4life]

We use ours for basic morphology identification, cell counts, viability tests, respiratory tests, gram stains, and plate inspections. As far as mutations, its kind of hard to tell from just looking at them. Mutations are usually identified in sensory tests. The more advanced stuff comes from using things like a UV/VIS spectrophotometer, a chromatograph, and PCR testing.

 

[ajdelange]

I can't speak for the pros but whenever beer is hazy a quick examination indicates whether the haze is yeast, protein particles, or bacteria.

The various strains have particular morphologies so that if you get familiar with the morphology of the strain you are using you an quickly spot yeast cells that don't belong.

Oxalate crystals are pretty easy to spot if you have those.

Healthy and not so healthy cells stain differentially so you can estimate cell vitality.

 

[FLJohnson]

I'm not familiar with respiratory tests that utilize a microscope. And how is a vitality test performed? I'm only familiar with viability testing with methylene blue or similar stain.

 

[Sourz4life]

You can do it on plates and on a hemocytometer. Using sodium dihydrogen phosphate, sodium hydrogen phosphate, and triphenyltetrazolium. When you stain them cells that don't change color have a respiratory mutation. Didn't mean to put vitality in mine, I always say those two together for some reason. But I do AP tests to determine vitality.