In this second in our series on beer microbiology, after understanding where contamination of draft beer typically comes from, we give you a look at 5 groups of microbes that can spoil your perfect pint. 1. Lactobacillus & Pediococcus What are they? Lactobacillus and Pediococcus are both genera of gram-positive lactic acid bacteria which infect beer. In some beers - particularly sour beers - they are actually used as part of the fermentation process, but this is a difficult