Originally Posted by jaapie
I have seen the opposite, going to very light. Are you sure they are Brett strains? How did you profile them?
Huh, that's interesting.
I putatively identify Sacc (and maybe others?) vs Brett first by collecting everything on an agar plate with either no drugs or just antibiotic to inhibit bacterial growth. Then I streak out individual colonies on a plate with cycloheximide and bromocresol green. The Brett guys are going to be cycloheximide resistant and white to light blue in color.
I then grow them in liquid culture and look at the morphology under a microscope. I've asked a few friends that study Sacc, and they've all said 'definitely not Sacc'. I showed one to a guy that studies Brett and he agreed that it's more than likely a Brett strain.
Most of what I collect seems to be sensitive to cycloheximide and grow blue/dark blue on bromocresol green. More than the opposite. It also seems to be a bit temp and location dependent.
Sure this doesn't definitively identify these guys as Brett, but I think very few other yeast will fall into this profile. Haven't done any PCR yet, but may once I find a strain that makes a good beer that I like.
All that plusthey don't taste like a Sacc beer!
I'm not a yeast geneticist, but this is what I've gathered from talking to yeast people and doing a bit of reading of the literature.