Organization and regulation of genes for amino acid biosynthesis in lactic acid bacteria

Abstract

The recent description of large clusters of biosynthetic genes in the chromosome of Lactococcus lactis and, to a lesser extent, of Lactobacillus, has brought some information on gene organization and control of gene expression in these organisms. The genes involved in a given amino acid biosynthetic pathway are clustered at a single chromosomal location and form an operon. Additional genes which are not required for the biosynthesis are present within some operons. Genetic signals are, in general, similar to those found in other prokaryotes. Several systems controlling gene expression have been identified and transcription attenuation seems frequent. Among the attenuation mechanisms identified, one resembles that controlling amino acid biosynthesis in many bacteria by ribosome stalling at codons corresponding to limiting amino acid. The others are different and might be related to a new class of attenuation mechanism. Preliminary evidence for a new type of regulatory mechanism, involving a metabolic shunt, is also reviewed.

Comparison of ?-acetolactate synthase and ?-acetolactate decarboxylase in Lactococcus spp. and Leuconostoc spp.

“…~uc~~Iuc~s, Also, several compounds were tested as potential effectors for ALDC. The gone encoding ALDC has been recently identified in a Lacrococcus la&s strain which did not require Icucine, isoleucine and valine for growth (Chopin, 1993). The 3 branched-chain amino acids (leucine, isofeucine and valine) were found to be activators for L. la&s subsp.…”

“…ALDC activity was assayed with 3.6 mM ALA. No effect was observed with NAD(P), NAD(P)H, ATP and ADP. kiac~ccus strains isolated from dairy products are auxotrophic for b~ch~-chin amino acids, this aux~~y resulted from accurnu~~ muttons and deletions within the amino acid b~~n~etic genes (Chopin, 1993) which might be a consequence of the adaptation of dairy lactococci to milk or dairy products. luctis biovar.…”

Proteolytic activities, peptide utilization and oligopeptide transport systems of wild Lactococcus lactis strains

“…Sixteen L. lactis strains grew without Met after 48 h. Since none of the L. lactis strains was able to grow without Leu or Val, peptides used in growth experiments were chosen to serve as sources of these specific amino acids. The requirement for amino acids is strain dependent and can vary from 4 up to 14 different amino acids (Chopin, 1993). Although amino acid auxotrophies were not exhaustively studied in this work (only six amino acids were tested), some conclusions could be drawn.…”

“…However, these authors recorded growth in absence of Leu in 10 out of 12 (Ayad et al, 1999) and in 14 out of 32 (Morales et al, 2003) wild L. lactis strains. The growth in absence of Ile can be explained by the fact that Ile synthesis from Val requires just one additional enzyme, while three additional enzymes are required for Leu synthesis (Chopin, 1993).…”

Lactobacillus helveticus: importance in food and health

“…To this regard, the review of Griffiths and Tellez (2013) described more specifically the role of the proteolytic system in L. helveticus . L. helveticus is among the most nutritionally fastidious LAB, requiring 14 exogenous aminoacids (Chopin, 1993). To assure its nutritional requirements when grown in milk, L. helveticus relies on a potent proteolytic system capable of producing short peptides and liberating amino acids from casein (Callanan et al, 2008).…”