Transcriptional analysis of the cyclopropane fatty acid synthase gene of Lactococcus lactis MG1363 at low pH

• Published in: FEMS microbiology letters 2005-09, Vol.250 (2), p.189-194
• Main Authors: Budin-Verneuil, Aurélie, Maguin, Emmanuelle, Auffray, Yanick, Ehrlich, S. Dusko, Pichereau, Vianney
• Format: Article
• Language: English
• Subjects: Acid stress; Acidity; Adaptation, Physiological; Adenosylmethionine; Bacteriology; Base Sequence; beta-Galactosidase; beta-Galactosidase - genetics; Biogenesis of cell structures, supramolecular organization; Biological and medical sciences; Cloning; Cyclopropane; DNA, Bacterial; E coli; Escherichia coli; Fatty acid modification; Fatty acids; Fatty-acid synthase; Fundamental and applied biological sciences. Psychology; Galactosidase; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Genes, Reporter; Hydrogen-Ion Concentration; Lactic acid bacteria; Lactococcus lactis; Lactococcus lactis - enzymology; Lactococcus lactis - genetics; Life Sciences; Ligases; Ligases - genetics; Methionine Adenosyltransferase; Methionine Adenosyltransferase - genetics; Methyltransferases; Methyltransferases - genetics; Microbiology; Microbiology and Parasitology; Molecular Sequence Data; Operon; pH effects; Promoter Regions, Genetic; Recombinant Fusion Proteins; S-Adenosylmethionine; Stationary phase; Transcription; Transcription, Genetic; Up-Regulation; β-Galactosidase
• ISSN: 0378-1097; 1574-6968
• DOI: 10.1016/j.femsle.2005.07.007

Cyclopropane fatty acid synthase (cfa) catalyses the transfer of a methyl group from S-adenosylmethionine (SAM) to unsaturated fatty acids. Northern blot experiments demonstrated that the Lactococcus lactis MG1363 cfa gene is mainly expressed as a bicistronic transcript together with metK, the gene encoding SAM synthetase, and is highly induced by acidity. The cfa promoter was characterized by 5′-RACE PCR, and fused to β-galactosidase by cloning into the pAK80 plasmid. This transcriptional fusion was highly induced by acidity (23-fold at pH 5) as well as during entry into the stationary phase (8-fold) in L. lactis. Interestingly, the cfa promoter expression is repressed in a L. lactis relA* mutant which accumulates (p)ppGpp, whereas its induction by acidity appeared independent of (p)ppGpp in L. lactis and in Escherichia coli.