Off topic - concerning airborne yeast, that is the way beer was originally fermented, in open containers, with the aid of naturally occurring airborne yeasts. This was before folk even knew of te existence of yeast. Now THERE'S a divine reaction one could base a plausible religion on!
Also, when brewing became more sophisticated, it was common for brewing to be restricted during the warmer seasons to minimize "contamination" by undesireable yeasts. Tho I do not have the cites before me, I believe the marzenbier traditionally featured at Oktoberfest was the "last" beer from the previous brewing season, and Oktoberfest sort of kicked off the new season.
55gal - Coralife 4x65w cf, xp3, flourite, Hydor ETH300w, pressurized CO2 w/ rex(TM) reactor!
30gal - 55W AH, ecco 2232, flourite/gravel, DIY CO2 w/ Hagen ladder
3gal - endlers/cherry shrimp
4W cf, Red Sea deco nano, flourite