Mutational analysis of exopolysaccharide biosynthesis by Lactobacillus sakei 0-1

• Published in: FEMS microbiology letters Vol. 169; no. 2; pp. 241 - 249
• Main Authors: Breedveld, M, Bonting, K, Dijkhuizen, L
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 15.12.1998; Blackwell; Oxford University Press
• Subjects: Bacterial Capsules - biosynthesis; Bacteriology; Biological and medical sciences; Biosynthesis; Cell morphology; Cell walls; Cytology; dTDP‐rhamnose; Ethyl Methanesulfonate; Exopolysaccharides; Extracellular polysaccharide; food microbiology; food processing; Fundamental and applied biological sciences. Psychology; Glucokinase - metabolism; Glucose - biosynthesis; Hydro-Lyases - metabolism; Lactic acid bacterium; Lactobacillus - drug effects; Lactobacillus - metabolism; Lactobacillus sakei; meat products; Metabolism. Enzymes; Microbiology; Microscopy, Electron; Morphology; Mutagens; Mutants; Mutation - drug effects; Non‐ropy mutant; Nucleotidyltransferases - metabolism; Phosphoglucomutase - metabolism; Polysaccharides, Bacterial - biosynthesis; Rhamnose; Rhamnose - biosynthesis; Sulfonic acid; Temperature dependence; UDP‐glucose; Extracellular polysaccharide; Lactic acid bacterium; dTDP-rhamnose; Non-ropy mutant; UDP-glucose; Lactic acid bacteria; Enzymatic activity; Morphology; Bacteria; Lactobacillaceae; Biosynthesis; Mutation; Metabolism; Extracellular; Lactobacillus sake; Polysaccharide; Cell wall
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1111/j.1574-6968.1998.tb13324.x

Lactobacillus sakei strain 0-1 produces an exopolysaccharide (EPS) consisting of glucose and rhamnose in a ratio of 3:2. As part of a biochemical and molecular analysis of the EPS biosynthetic pathway in L. sakei strain 0-1, we have isolated a random set of EPS-negative mutants. Following treatment of cells with the mutagen ethylmethane sulfonic acid, a total of 10 mutants were identified that lacked the clear ropy appearance of wild-type colonies on agar plates. Their characterization revealed that eight mutants had completely lost the ability to synthesize the normal EPS. Six of these mutants lacked activities of enzymes involved in the biosynthesis of dTDP-rhamnose, required for EPS production. Only mutant strains 12 and 20 were directly affected in EPS synthesis. Strain 12 synthesized EPS with a different sugar composition, however. Interestingly, strain 12 showed temperature-dependent EPS synthesis, with the highest amounts synthesized at 12 degrees C, and low amounts at the optimal temperature for growth (30 degrees C). Two mutants were in fact EPS-positive, producing the normal EPS, but displayed a different cell morphology (elongated cells), indicating a modification in cell wall synthesis.