I have read recommendations on Amazon.com about the yeast book and that's what I thought - a basic intro book which is not what I want. Thanks for the link to the yeast page. I haven't read it yet but I'm not really looking into improving my yeast culturing. I want to know how microbreweries keep "house strains". They must put them under a microscope and culture them from there, but how can they differentiate b/w the yeast they want and other yeasts/bacteria and isolate them. I just don't really get that. I mean does anyone not buy yeast from wyeast/white labs b/c they maintain a steady house strain?
A lot of breweries store their house strains with wyeast/white labs, and get fresh pitches as needed. They will generally repitch as many as 7-20 times, and since they split it after each batch that can account for a lot of batches. Most breweries don't do any culturing at all.
There are a number of tests you can do for your strain of choice, and you get used to that strains performance and can tell when it is deviating from what you expect. But you can do viability staining and look under a scope, sure. For contaminants, looking under a microscope is not the best way to go. A very small portion of bacteria or wild yeast can have a significant effect on the finished beer, and it could easily be overlooked when it is in the beginning stages of contamination.
Another thing you can do is plate it and look at the colonies. Colony morphology can tell you a lot about the health of the culture, and even the smell of the plates can vary quite a bit between different strains.
Obviously I don't know what every brewery in the country does, but the ones around here tend to do what I've mentioned above.