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Global regulatory mutations in csrA and rpoS cause severe central carbon stress in Escherichia coli in the presence of acetate
- Source :
- Journal of bacteriology. 182(6)
- Publication Year :
- 2000
-
Abstract
- The csrA gene encodes a small RNA-binding protein, which acts as a global regulator in Escherichia coli and other bacteria (T. Romeo, Mol. Microbiol. 29:1321–1330, 1998). Its key regulatory role in central carbon metabolism, both as an activator of glycolysis and as a potent repressor of glycogen biosynthesis and gluconeogenesis, prompted us to examine the involvement of csrA in acetate metabolism and the tricarboxylic acid (TCA) cycle. We found that growth of csrA rpoS mutant strains was very poor on acetate as a sole carbon source. Surprisingly, growth also was inhibited specifically by the addition of modest amounts of acetate to rich media (e.g., tryptone broth). Cultures grown in the presence of ≥25 mM acetate consisted substantially of glycogen biosynthesis ( glg ) mutants, which were no longer inhibited by acetate. Several classes of glg mutations were mapped to known and novel loci. Several hypotheses were examined to provide further insight into the effects of acetate on growth and metabolism in these strains. We determined that csrA positively regulates acs (acetyl-coenzyme A synthetase; Acs) expression and isocitrate lyase activity without affecting key TCA cycle enzymes or phosphotransacetylase. TCA cycle intermediates or pyruvate, but not glucose, galactose, or glycerol, restored growth and prevented the glg mutations in the presence of acetate. Furthermore, amino acid uptake was inhibited by acetate specifically in the csrA rpoS strain. We conclude that central carbon flux imbalance, inhibition of amino acid uptake, and a deficiency in acetate metabolism apparently are combined to cause metabolic stress by depleting the TCA cycle.
- Subjects :
- Physiology and Metabolism
Citric Acid Cycle
Sigma Factor
Biology
Gene mutation
Acetates
Microbiology
Bacterial Proteins
Genes, Regulator
Escherichia coli
Isocitrate lyase activity
Glycolysis
CsrA protein
Amino Acids
Molecular Biology
Escherichia coli Proteins
Glyoxylates
RNA-Binding Proteins
Metabolism
Gene Expression Regulation, Bacterial
Carbon
Culture Media
Citric acid cycle
Repressor Proteins
Biochemistry
Gluconeogenesis
Genes, Bacterial
Mutation
rpoS
Glycogen
Subjects
Details
- ISSN :
- 00219193
- Volume :
- 182
- Issue :
- 6
- Database :
- OpenAIRE
- Journal :
- Journal of bacteriology
- Accession number :
- edsair.doi.dedup.....030305e84c8f420abeec17bd02959b77