Multiple nutritional requirements of lactobacilli: genetic lesions affecting amino acid biosynthetic pathways

Abstract

Genetic lesions responsible for amino acid requirements in several species of multiple auxotrophic lactobacilli were investigated. Systematic attempts were made to isolate mutants that could grow in the absence of each of the amino acids required by the parental strains of Lactobacillus plantarum, L. casei, L. helveticus, and L. acidophilus. After treatment with appropriate mutagens, such mutants could be obtained with respect to many but not all required amino acids. Successful isolation of mutants for a given amino acid means that a minor genetic lesion reparable by single-step mutations affects its biosynthesis; a failure to isolate mutants suggests the involvement of more extensive lesions. Analysis of these results as well as the specific requirements exhibited by the parental strains revealed certain regularities; some of the biosynthetic pathways for individual amino acids were virtually unaffected by more extensive lesions in at least species tested, whereas others were affected by more extensive lesions in at least some species. Both the number and the kind of pathways affected by extensive lesions differed appreciably among different species. Furthermore, the growth response of the parental strains to some putative amino acid precursors revealed a clear correlation between the extent of genetic lesions and the occurrence and location of a genetic block(s) for a given pathway. These findings are discussed in relation to the phylogeny, ecology, and evolution of lactic acid bacteria.

Amino acid transport in Lactobacillus helveticus

“…Fourteen amino acids have been reported to be essential or growth stimulating for L. helveticus [2]. The transport of all these amino acids except methionine was studied in whole cells.…”

“…Lactobacilli require many nutrients including several amino acids in the growth media [2]. L. helveticus can grow in milk which contains only small quantities of free amino acids and possesses a proteolytic system to release amino acids from the milk protein, casein [3,4].…”

Comparative effects of exopolysaccharides from lactic acid bacteria and fructo-oligosaccharides on infant gut microbiota tested in an in vitro colonic model with immobilized cells

“…EPS production and quantification were carried out as described by Bergmaier et al (2001). Briefly, the strain was subcultured twice in MRS broth medium before being inoculated at 10% (volume in volume, v/v) in basal minimum medium (BMM) (Morishita et al, 1981) supplemented with glucose (40 g L À1 ) and tryptone (2 g L À1 ) in a 15 L working-volume bioreactor (Inox-tech Inc., Montreal, QC). Fermentation was carried out aerobically at 37 1C and controlled at pH 6 by the addition of 6 N NH 4 OH for 48 h. The fermented medium was then heated at 100 1C for 15 min in order to inactivate bacteria and to denature EPSdegrading enzymes, cooled and centrifuged (25 min, 13 200 g) to remove bacteria.…”

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

“…The study of the nutritional requirements of lactic acid bacteria has been made possible following the early development of chemically defined media allowing growth of Lactococcus lactis [7][8][9][10][11] or various species of lactobacilli including some of those used in food fermentations [12][13][14][15]. All these media contain, in addition to mineral salts and glucose, amino acids, vitamins and nu-cleic acid bases.…”