Microbes in yeast...
Err... Saccharomyces cerevisiae is not a microbe. It is a eucariote.
At least so I remember from the days when I was still undecided if I will go to the darkside and do IT or to the light side and help humanity in their fight against diseases. My first salaried job (while still in high school) was a lab assistant in a mol biol lab and I fondly remember my attempts to dupe that damn "microbe" into producing human gamma interferon. Not an easy task by the way as it is quite fussy to what DNA it will incorproate (not like microbes which you can engineer with plasmids or phages in many weird and wonderful ways).
As far as the strain of yeast not being important, that is b*llocks. One of the reasons why soviet beer with the exemption of the stuff from the Baltics used to suck rocks is exactly because most factories were mandated to use a mutant strain (so that people do not try to seed their home potato fermenter with it). The mutant was producing excessive stinky bits (ketones) if you did not keep the pH acidic enough so the average Vovka without access to food quality phosphoric acid could not do some DIY brewing.
Granted, that is an extreme example, however as every brewer knows there is yeast that produces nice healthy beer and wine and there is yeast that produces ourtight stinkers (even without the bloody soviet "anti-DIY brewing" mod).