Search

The relA gene of Escherichia coli encodes guanosine 3',5'-bispyrophosphate (ppGpp) synthetase I, a ribosome-associated enzyme that is activated during amino acid starvation. The stringent response is thought to be mediated by ppGpp. Mutations in relA are known to result in pleiotropic phenotypes. We now report that three different relA mutant alleles, relA1, relA2, and relA251::kan, conferred temperature-sensitive phenotypes, as demonstrated by reduced plating efficiencies on nutrient agar (Difco) or on Davis minimal agar (Difco) at temperatures above 41[degrees]C. The relA-mediated temperature sensitivity was osmoremedial and could be completely suppressed, for example, by the addition of NaCl to the medium at a concentration of 0.3 M. The temperature sensitivities of the relA mutants were associated with decreased thermotolerance; e.g., relA mutants lost viability at 42[degrees] C, a temperature that is normally nonlethal. The spoT gene encodes a bifunctional enzyme possessing ppGpp synthetase and ppGpp pyrophosphohydrolase activities. The introduction of the spoT207::cat allele into a strain bearing the relA251::kan mutation completely abolished ppGpp synthesis. This ppGpp null mutant was even more temperature sensitive than the strain carrying the relA251::kan mutation alone. The relA-mediated thermosensitivity was suppressed by certain mutant alleles of rpoB (encoding the [beta] subunit of RNA polymerase) and spoT that have been previously reported to suppress other phenotypic characteristics conferred by relA mutations. Collectively, these results suggest that ppGpp may be required in some way for the expression of genes involved in thermotolerance.

Examines the temperature-sensitive growth and decreased thermotolerance associated with relA gene mutations in Escherichia coli. Types of relA mutant alleles; Suppression of the relA-mediated thermosensitivity; Osmoremediation of relA-mediated temperature-sensitive growth.

Studies the involvement of the N terminus of ribosomal protein L11 in regulation of the RelA protein of Escherichia coli. Effects of N-terminal deletion fragment of L11 protein on stringent response and accumulation of ppGpp; Influence of proline-rich helix of L11 on RelA regulation; Effect of 'L11 on RelA-ribosome interaction.

Provides information on a study of the temperature-sensitive penicillin reported in amino acid-deprived Escherichia coli. Information on the role of the heat shock response in temperature-dependent tolerance to ...-lactam antibiotics; Detailed information on the effect of temperature on priming and lysis induction stages of ampicillin-induced lysis; Conclusion reached for the basis of temperature sensitivity.

Analyzes the direct correlation between overproduction of guanosine 3',5'-bispyrophosphate (ppGpp) and penicillin tolerance in Escherichia coli. Effect of overproduction of ppGpp on phospholipid and peptidoglycan synthesis; Quantification of ppGpp; Effect of beta-lactam antibiotic treatment on ppGpp; Reversal of ppGpp-induced ampicillin tolerance.

Determines the role of phospholipid synthesis in peptidoglycan metabolism during growth of Escherichia coli. Dependence of peptidoglycan synthesis on phospholipid synthesis during growth; Induction of beta-lactam tolerance by cerulenin treatment of growing bacteria; Penicillin tolerance caused by inhibition of phospholipid synthesis.

Lipopolsaccharide was isolated from a phage-selected mutant of a wild strain of Aeromonas salmonicida by the aqueous phenol method. The lipopolysaccharide consisted of the R form, containing per mode, three moles of L-glycero-D-manno-heptopyranose, one mole of 3-deoxy-D-manno-2-octulosonic acid (dOclA) and lipid A. The dOclA was not fully assayable by the thiobarbituric acid methods usually used, but its degradation product was detected, after Smith degradation of lipopolysaccharide, either as free 3-deoxy-2-heptulosonic acid (after hydrolysis) or substituted by a mannopyranosyl residue derived from heptose. Mas spectrometry indicated that the dOclA existed in the furanose form and was substituted by the heptose triasaccharide through position six. Methylation analysis, chemical degradation, chromium trioxide oxidation and nuclear magnetic resonance spectroscopy were used to identify the structure of the core oligosaccharide as: LαDHepp(1→2)LαDHepp(1→3)LαD-Hepp(1→6)dOclAf(2→. [ABSTRACT FROM AUTHOR]

Focuses on the direct interaction of the Escherichia coli cytotoxin RelE with its specific antidote, RelB. Cloning of relB and relE into expression vectors; Toxicity of RelE; Overexpression and copurification of RelB and RelE; Purification of RelB and RelE.

Presents information on the Escherichia coli LytB protein. Reference to the occurrence of homologs of the Escherichia coli coli lytB gene; Information on a southern blot analysis of chromosomal deoxyribonucleic acid with Escherichia coli lytB gene.