Well, first things first:
Brettanomyces is actually a yeast, meaning that it takes sugar (6-carbon ring) and converts it to alcohol (ethanol, a 2-carbon product) and Carbon Dioxide. There are something like 12 strains of
Brett that have been classified, but only 4 are used for beer/wine fermentation:
B. claussenii, B. bruxellensis, B. lambicus, and B. anomalous.
Clausenii is the most mild of the Bretts, along with anomalous. It gives a mild pineapple/horsey flavor to a finished product, when used in secondary fermentation.
Bruxellensis is the Brett that Orval adds in secondary/bottling to give it its trademark flavor. I find this to be the most barnyard/funky in that sense of the strains.
With Lambicus, I find that it is the only one to produce a lactic type flavor, even though it is not a bacteria - it is giving me high levels of cherry-like flavors when used in secondary (I have two
B. lambicus beers going right now.
When talking about lactic sourness, that comes from both the
lactobacillus and
pediococcus bacteria. They take sugars (lactose) and convert them to lactic acid. Common types of this is yogurt and buttermilk which have had some of their sugars converted to lactic acid, giving them their trademark "twang."
The vinegar taste comes from acetic acid. All household white vinegar is is a 5% solution of acetic acid. This comes from acetobacter, which isn't directly innoculated into the beer from cultures, but arises out of oxidation of the product. Sometimes this is desirable (such a a Flanders Red) and sometimes it isn't.
This is the basics of it all - but I would suggest you pick up
Wild Brews by Jeff Sparrow if you want the detailed information.
