title: Transcriptome, proteome, and metabolite analyses of a lactate dehydrogenase-negative mutant of Enterococcus faecalis V583.
abstract: A constructed lactate dehydrogenase (LDH)-negative mutant of Enterococcus faecalis V583 grows at the same rate as the wild type but ferments glucose to ethanol, formate, and acetoin. Microarray analysis showed that LDH deficiency had profound transcriptional effects: 43 genes in the mutant were found to be upregulated, and 45 were found to be downregulated. Most of the upregulated genes encode enzymes of energy metabolism or transport. By two-dimensional (2D) gel analysis, 45 differentially expressed proteins were identified. A comparison of transcriptomic and proteomic data suggested that for several proteins the level of expression is regulated beyond the level of transcription. Pyruvate catabolic genes, including the truncated ldh gene, showed highly increased transcription in the mutant. These genes, along with a number of other differentially expressed genes, are preceded by sequences with homology to binding sites for the global redox-sensing repressor, Rex, of Staphylococcus aureus. The data indicate that the genes are transcriptionally regulated by the NADH/NAD ratio and that this ratio plays an important role in the regulatory network controlling energy metabolism in E. faecalis.
authors.affiliation: Laboratory of Microbial Gene Technology and Food Microbiology, Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, N-1432 Ås, Norway.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Mehmeti
authors.forename: Maria
authors.initials: M
authors.lastname: Jönsson
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Fergestad
authors.forename: Geir
authors.initials: G
authors.lastname: Mathiesen
authors.forename: Ingolf F
authors.initials: IF
authors.lastname: Nes
authors.forename: Helge
authors.initials: H
authors.lastname: Holo
mesh_terms: D000093:Acetoin / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D013293:Enterococcus faecalis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D005285:Fermentation; D005561:Formates / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000172:deficiency*; D055442:Metabolome; D046228:Microarray Analysis; D009243:NAD / Q000378:metabolism; D020543:Proteome / Q000032:analysis*
chemical_list: D005561:Formates; D020543:Proteome; D009243:NAD; C030544:formic acid; D000093:Acetoin; D007770:L-Lactate Dehydrogenase; D005947:Glucose