Which probably means you have not come in contact with the red wine making. Brettanomyces sp. are wild yeasts that infect wineries and wine. Too much of brett growth means too much phenols and eventual degradation of the wine's aroma. The volatile phenols give wine that "earthiness" and "yeastiness", which also is frequently described as "mouse droppings" :-)
Supposedly, a limited brett growth can enrich bouquet and make a wine better but that's a balancing act that's almost impossible to control.
Interesting. If this beer is any good, I'd guess it is a difficult one to make.
DK