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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Amino acid starvation of cells of the Escherichia coli relA strain, CP79, which cannot accumulate guanosine tetraphosphate (ppGpp) in response to amino acid limitation, increased the pEG1 plasmid content about 5- to 7-fold in comparison with exponentially growing cells (pEG1:pBR322 with an insertion of Bacillus amyloliquefaciens DNA coding for beta-glucanase). In contrast, no pEG1 amplification occurred in E. coli CP78, the stringently controlled counterpart, after amino acid starvation. In order to verify these results, the plasmid DNA content was monitored by measuring the expression of pEG1-encoded beta-glucanase from B. amyloliquefaciens both before and after plasmid amplification. When amino acid starved CP79 cells were given an additional dose of amino acids, a more than 10-fold increase in pEG1-encoded beta-glucanase activity (per cell mass) was measured. This increase in enzyme activity correlates with pEG1 amplification during amino acid limitation. Under comparable conditions the activity of beta-glucanase was not increased in strain CP78, which did not amplify the plasmid. We suggest that the replication of pEG1 in amino acid starved E. coli cells is somehow under negative control by ppGpp. Moreover, we found the Bacillus beta-glucanase in E. coli relA cells to be excreted into the growth medium after starvation and overexpression.
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PMID:Expression of a cloned beta-glucanase gene from Bacillus amyloliquefaciens in an Escherichia coli relA strain after plasmid amplification. 307 39

Amino acid-starved cells of Escherichia coli relA+, which contain a large number of glycogen particles, are able to survive in phosphate buffer for a longer time period than their relaxed counterparts. With regard to NH4+ starvation differences in the survival of both strains were not found. NH4+ starved cells of E. coli relA are able to synthesize glycogen but amino acid-starved cells of the relA strain are not. We suggest that the synthesis of glycogen triggered by guanosine tetraphosphate during amino acid starvation is responsible for the prolonged viability of the E. coli relA+ strain.
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PMID:Role of relA mutation in the survival of amino acid-starved Escherichia coli. 351 32

When starved for leucine, strains of Bacillus subtilis do not complete chromosome replication to the terminus. The amount of deoxyribonucleic acid (DNA) made poststarvation is characteristic of the strain. In this study, four strains differing in their DNA response were examined for ribonucleic acid (RNA) regulation during leucine starvation. Each of the strains was judged to be stringent for RNA control based on the amount of RNA made poststarvation. Sucrose gradient profiles on RNA made with and without leucine starvation support this conclusion. Accumulation of guanosine tetraphosphate during leucine starvation showed no correlation with the amount of DNA synthesized. We concluded that modulation control of DNA synthesis during leucine starvation is independent of RNA control.
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PMID:Effects of leucine starvation on control of ribonucleic acid synthesis in strains of Bacillus subtilis differing in deoxyribonucleic acid regulation. 420 Aug 61

Accumulation of guanosine tetraphosphate (ppGpp) in Escherichia coli strain AS19 valS, carrying a temperature-sensitive valyl-transfer ribonucleic acid synthetase and infected with bacteriophage T7, was studied. Valine starvation was achieved by culturing this strain at 42 C. Addition of rifampin to an uninfected culture at the nonpermissive temperature resulted in loss of accumulated ppGpp; however, cultures infected with phage T7, treated with rifampin, and then shifted to the nonpermissive temperature maintained the ability to accumulate ppGpp. Moreover, treatment of the T7-infected culture with rubidomycin, an antibiotic which inhibits transcription, did not reduce the amount of ppGpp accumulated following shift to the nonpermissive temperature. Measurements of the instantaneous rate of T7 transcription showed that it is not under stringent control of amino acids. ppGpp synthesized in T7-infected E. coli appears to be more stable than its counterpart in an uninfected culture. These results are interpreted to mean that ppGpp production is not directly dependent on transcription and arises instead from inhibition of another reaction, most likely some aspect of translation.
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PMID:Accumulation of guanosine tetraphosphate in T7 bacteriophage-infected Escherichia coli. 457 Jun 2

Serine hydroxamate, which inhibits the charging of seryl-transfer ribonucleic acid, reduced the synthesis of phospholipid and nucleic acids in Escherichia coli. This effect was analogous to depriving amino acid auxotrophs of their nutritional requirement and appears to be a manifestation of the stringent response shown by rel(+) strains of E. coli. Amino acid starvation (serine or methionine) alone or serine hydroxamate treatment alone results in 60 to 80% inhibition of lipid accumulation, 90% inhibition of ribonucleic acid accumulation, and an increase in guanosine tetraphosphate (ppGpp). These three effects were reversed by addition of chloramphenicol (CM). A combination of serine starvation and serine hydroxamate treatment resulted in inhibition of lipid and RNA accumulation as well as an increase in ppGpp, but the consequences of the double block were not reversed by CM. We conclude that a strong interrelationship exists among these processes and that CM acts to relax a stringent response by mechanisms other than interference with ppGpp formation. All species of phospholipid were affected by a stringent response evoked by amino acid starvation or addition of serine hydroxamate, but in all cases the synthesis of phosphatidylethanolamine was most severely inhibited. Serine hydroxamate was not incorporated into lipid but specifically caused phosphatidylserine accumulation. Serine starvation produced a dramatic alteration of the distribution of isotope incorporated into phospholipid, which resulted from the stringent response compounded with the limitation of a substrate for phosphatidylserine synthesis.
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PMID:Effect of serine hydroxamate on phospholipid synthesis in Escherichia coli. 457 13

To determine the stringent response, a repression of gene activity during amino acid starvation assumed to be mediated by the effector necleotide guanosine tetraphosphate (ppGpp), of metabolically regulated constitutive genes, we measured the transcription of ribosomal protein genes, the constitutive lac operon, and stable RNA genes in a variety of growth media and after amino acid starvation in a relA+/relA pair of Escherichia coli B/r strains. For rRNA and tRNA (stable RNA) it has previously been shown that the distinction between stringent control and growth rate control is unfounded, as the function describing the stable RNA gene activities at different concentrations of guanosine tetraphosphate is independent of growth conditions (exponential growth or amino acid starvation) and of the relA allele present. Here, the results indicated that the stringent responses of ribosomal protein genes and lac differ from their metabolic control during exponential growth in different media. This can be explained by polarity and RNA polymerase sink effects during amino acid starvation which are irrelevant for stable RNA genes but which are superimposed on mRNA gene activities.
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PMID:Transcription of ribosomal component genes and lac in a relA+/relA pair of Escherichia coli strains. 609 Mar 95

During uridine starvation in Escherichia coli K12, the rate of RNA accumulation comes down to about 7% of the nonstarved rate. This is achieved, in part, by an eight-fold increase in the assembly time of stable RNA molecules. However, the assembly time of mRNA molecules is not enhanced as much, being longer by a factor of 3 in starved cells compared to nonstarved ones. It, therefore, appears that the rate of synthesis of these two RNA species is noncoordinately controlled during uridine starvation. This control does not seem to be mediated by guanosine tetraphosphate.
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PMID:Noncoordinate control of the synthesis of different species of RNA in Escherichia coli K12 during uridine starvation. 615 81

Parameters relating to RNA synthesis were measured after a temperature shift from 30 to 42 degrees C, in a relA+ and relA- isogenic pair of Escherichia coli strains containing a temperature-sensitive valyl tRNA synthetase. The following results were obtained: (i) the rRNA chain growth rate increased 2-fold in both strains; (ii) newly synthesized rRNA became unstable in both strains; (iii) the stable RNA gene activity (rRNA and tRNA, measured as stable RNA synthesis rate relative to the total instantaneous rate of RNA synthesis) decreased 1.7-fold in the relA+ strain and increased 1.9-fold in the relA mutant; and (iv) the RNA polymerase activity (measured by the percentage of total RNA polymerase enzyme active in transcription an any instant) decreased from 20 to 3.6% in the relA+ strain and remained unchanged (or increased at most to 22%) in the relA mutant. It is suggested that both rRNA gene activity and the RNA polymerase activity depend on the intracellular concentration of guanosine tetraphosphate, whereas the altered chain elongation rate and stability of rRNA are temperature or amino acid starvation effects, respectively, without involvement of relA function.
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PMID:relA-dependent RNA polymerase activity in Escherichia coli. 617 1

The expression of stable RNA (rRNA and tRNA) genes and the concentration of guanosine tetraphosphate (ppGpp) were measured in an isogenic pair of relA+ and relA derivatives of Escherichia coli B/r. The cells were either growing exponentially at different rates or subject to amino acid starvation when they were measured. The specific stable RNA gene activity (rs/rt, the rate of rRNA and tRNA synthesis relative to the total instantaneous rate of RNA synthesis) was found to decrease from 1.0 at a ppGpp concentration of 0 (extrapolated value) to 0.24 at saturating concentrations of ppGpp (above 100 pmoles per optical density at 460 nm unit of cell mass). The same relationship between the rs/rt ratio and ppGpp concentration was obtained independent of the physiological state of the bacteria (i.e., independent of the growth rate or of amino acid starvation) and independent of the relA allele. It can be concluded that ppGpp is an effector for stable RNA gene control and that stable RNA genes are not controlled by factors other than the ppGpp-mediated system. The results were shown to be qualitatively and quantitatively consistent with data on in vitro rRNA gene control by ppGpp, and they were interpreted in the light of reported ideas derived from those in vitro experiments.
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PMID:Control of rRNA and tRNA syntheses in Escherichia coli by guanosine tetraphosphate. 617 24

The effects of two polypeptide antibiotics, polymixin B and gramicidin S, on the intracellular pool size and turnover of guanosine tetraphosphate (ppGpp) were analyzed in stringent (relA+) and relaxed (relA) strains of Escherichia coli. When either one of these two drugs was added to stringent bacteria cultures at a final concentration that blocked protein and RNA synthesis, ppGpp was found to accumulate. Under similar conditions of inhibition of macromolecular synthesis, ppGpp also appeared to accumulate in relaxed bacteria. Moreover, in either type of strain, no significant accumulation of guanosine pentaphosphate (pppGpp) could be detected upon drug treatment. It was, therefore, concluded that polymixin and gramicidin elicit ppGpp accumulation through a mechanism independent of the relA gene product and, consequently, quite distinct from the stringent control system triggered by amino acid starvation. Further experiments performed by using tetracycline as an inhibitor of ppGpp synthesis, showed that the increase in the level of this nucleotide induced by drug action was due, in fact, to a strong restriction of its degradation rate.
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PMID:Accumulation of guanosine tetraphosphate induced by polymixin and gramicidin in Escherichia coli. 618 93


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