Brettanomyces Bruxellensis

Brettanomyces bruxellensis is a yeast associated with and named after, the Senne valley near Brussels, Belgium and is commonly found in Lambic.
It is, what many call, a 'wild' yeast, which means you can find it anywhere in nature.
Brett. Brux. can produce an acid by metabolizing oxygen and ethanol, but is should be said that Brett. Brux is not what makes a sour-beer real sour, bacteria as lactobaccillus and Pediococcus is mostly responsible for producing acids that makes a real sour beer.
A Brettanomyces can chew on larger sugarchains and therefor we use it as a secondary fermenter.
The flavor a Brettanomyces leaves in the beer is mostly described as 'Funky'.