Taxonomy of lactic acid bacteria

Lactic acid bacteria are Gram-positive non-sporing cocci, coccobacilli or rods, having a DNA base composition of less than 50 mol% G + C. They generally lack catalase, although pseudo-catalase was detected in cultures grown on a low sugar concentration, and they need a fermentable carbohydrate for growth. Glucose is converted mainly to lactic acid (homofermentatives), or to lactic acid, carbon dioxide, ethanol and/or acetic acid (heterofermentatives). The branches within lactic acid bacteria do not completely agree with the traditional classification schemes based on morphology and phenotypic characteristics. Lactic acid bacteria comprise the genera Aerococcus, Alloiococcus, Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, Streptococcus, Tetragenococcus, and Vagococcus. The genus Bifidobacterium will also be briefly considered here, although phylogenetically it belongs to the Actinomycetes subdivision of the Gram-positive eubacteria, comprising also Propionibacterium, Brevibacterium and the microbacteria. The latter taxa are only very distantly related to the genuine lactic acid bacteria