Back in my Ye Olde Malt Shovel days, we picked up a Brettanomyces contamination in the wheat beer we were making at the time (dirty bright tank, no sterile filter before pack, no pasteuriser). I reckon that this was the most fascinating thing I have ever observed in beer.
Contamination was very low level but as mentioned in this thread, brett strains are slow growing and can chomp away on carbohydrates that regular Saccharomyces culture yeasts can't. On average, on a six pack basis, three bottles dodged the bullet, two bottles got one cell only and the sixth got two or three. Each cell grew into a colony which didn't disperse through the beer. Instead, they formed little balls about the size of a chick pea that were gossamer thin but still very visible. you could roll them around the bottom of the bottle. In a six pack, half the beers were bretty and the other half weren't. And you could see which were which without removing the crown...
I liked the bretty ones. Personal taste I guess. The product was pulled from the shelves and the brand killed. The raspberry beer that's on the shelves at the moment is the first 'Mad Brewers' release since the bretty beer four or five years ago.
