There is a growing list of grape, must and wine associated bacteria that can play an important role in the perceived quality of finished wine. As winemaking styles are migrating away from sterile and controlled techniques towards a more non-interventionist and “natural” fermentation, more bacteria are becoming sporadically problematic. Careful observation and environmental management of these fermentation is necessary in order to prevent unwanted attributes arising. Understanding the ecology of these bacteria is a necessary prerequisite in delineating the beneficial, benign, unwanted or catastrophic growth of winery associated bacteria.