LactococcusandLactobacillus

Abstract

This scope of this chapter is limited to discussions of Lactobacillus, Lactococcus, Leuconostoc, Pediococcus, and Streptococcus thermophilus, and summarizes and abstracts the major areas of research of lactic acid bacteria. The historical association of the lactic acid bacteria with milk fermentation has encouraged a substantial amount of research on the biochemistry and genetics of lactose and milk protein catabolism. The genus Pediococcus contains a number of divergent species. The lac genes of S. thermophilus and Lactobacillus spp. are organized differently than those of E. coli. Extracellular protease production in Lactococcus lactis is an unstable and variable trait. The proteinases of lactic acid bacteria produce a complicated mixture of polypeptides that the bacteria must break down into individual amino acids. The finding that some lactic acid bacteria require peptides for growth correlates well with the intracellular location determined for the peptidases. To date, the nucleotide sequences of more than 50 genes isolated from lactic acid bacteria, primarily the lactococci and lactobacilli, are published and available in nucleic acid data banks. Many of these genes are discussed in the chapter. The authors hope that the chapter dissuades the reader from the commonly held belief that little is known about the biology, biochemistry, and genetics of lactic acid bacteria.