ABSTRACT
Lactic acid bacteria are a group that has as its main characteristic the fermentation of carbohydrates with the production of lactic acid. Originally, this group included four genera of great importance in the production of foods: Lactobacillus, Leuconostoc, Pediococcus and Streptococcus. All are Gram-positive, non-spore-forming, facultative anaerobic, catalase and oxidase-negative bacteria. Pediococcus and Tetragenococcus are the only lactic acid bacteria that divide in two perpendicular directions resulting in the formation of pairs and tetrads but never in chains. The cells are perfectly round and rarely ovoid, in contrast to other coccus-shaped lactic acid bacteria such as Leuconostoc, Lactococcus and Enterococcus. Streptococcus is one of the original genera of lactic acid bacteria, but most of the species of importance in foods were reclassified into the new genera Enterococcus and Lactococcus.
