bacteria

Bacteria constitute a very large group of prokaryotic (non nucleus-containing) microorganisms that are earth’s most prevalent, most ancient and extremeophilic life forms. In beer and brewing, bacteria are distinct from brewing yeast which are eukaryotic (nucleus-containing), a more complex form of life.



While bacteria’s hardiness and prevalence may present challenges to brewers wishing to minimize their influence on their beer’s flavor profiles, other modern brewers have embraced many of the bacteria that thrive in beer to produce "spontaneously fermented" products. Indeed most ancient beers must have had flavor profiles shaped by these bacteria. Today some brewers use isolated and purified cultures of preferred bacteria to inoculate their fermented beer or unfermented wort in a more controlled manner.



Among the most common bacteria used by brewers are Lactobacillus and Pediococcus, which is not desirable itself but is thought to "feed" Brettanomyces. Some brewers intentionally use acetobacteria to produce flavor profiles enhanced by vinegar notes, a practice important to Flanders red ales, some oud bruins, and the Kentucky common.