Brettanomyces, the wild “Funk” producing yeast genus, often just called “Brett”. Depending on the style of beer you are brewing Brett can be considered a spoilage yeast, contributing off flavours, while in other styles of beer such as lambics, saisons, and sour beers, the high ester production of Brett adds desirable characteristics. Again, if you are looking for more information about Brettanomyces or any other organism involved in the production of beer, please check out Milk the Funk.