Multiple control of the acetate pathway in Lactococcus lactis under aeration by catabolite repression and metabolites.
To explore the factors controlling metabolite formation under aeration in Lactococcus lactis, metabolic patterns, enzymatic activities, and transcriptional profiles of genes involved in the aerobic pathway for acetate anabolism were compared between a parental L. lactis strain and its NADH-oxidase-overproducer derivative. Deregulated catabolite repression mutans in the ccpA or pstH genes, encoding CcpA or its co-activator HPr, respectively, were compared with a parental strain, as well. Although the NADH-oxidase activity was derepressed in ccpA, but not in the pstH background, a mixed fermentation was displayed by either mutant, with a higher acetate production in the pstH variant. Moreover, transcription of genes encoding phosphotransacetylase and acetate kinase were derepressed, and the corresponding enzymatic activities increased, in both catabolite repression mutants. These results and the dependence on carbon source for acetate production in the NADH-oxidase-overproducer support the conclusion that catabolite repression, rather than NADH oxidation, plays a critical role to control acetate production. Furthermore, fructose 1,6-bisphosphate influenced the in vitro phosphotransacetylase and acetate kinase activities, while the former was sensitive to diacetyl. Our study strongly supports the model that, under aerobic conditions, the homolactic fermentation in L. lactis MG1363 is maintained by CcpA-mediated repression of mixed acid fermentation.
Lopez de Felipe
Felix
F
Instituto del Frío, Consejo Superior de Investigaciones Científicas, Ciudad Universitaria, 28040 Madrid, Spain. fxlopez@if.csic.es
Gaudu
Philippe
P
D000084:Acetate Kinase / Q000096:biosynthesis; D000085:Acetates / Q000378:metabolism*; D000332:Aerobiosis; D001426:Bacterial Proteins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D004794:Enzyme Repression; D005285:Fermentation; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D013294:Lactococcus lactis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000096:biosynthesis; D009247:NADH, NADPH Oxidoreductases / Q000096:biosynthesis; D010709:Phosphate Acetyltransferase / Q000096:biosynthesis; D012097:Repressor Proteins / Q000235:genetics
D000085:Acetates; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D009097:Multienzyme Complexes; D012097:Repressor Proteins; C069286:catabolite control proteins, bacteria; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D010709:Phosphate Acetyltransferase; D000084:Acetate Kinase