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Biomedical subjects

E Z Ron

Publications and source records attributed to E Z Ron.

At least 73 records · Page 4Linked to original sources
PubMed1982

Changes in cell dimensions during amino acid starvation of Escherichia coli.

Electron microscopic analysis was used to study cells of Escherichia coli B and K-12 during and after amino acid starvation. The results confirmed our previous conclusion that cell division and initiation of DNA replication occur at a smaller cell volume after amino acid starvation. Although during short starvation periods, the number of constricting cells decreased due to residual division, it appears that during prolonged starvation, cells of E. coli B and K-12 were capable of initiating new constrictions. During amino acid starvation, cell diameter decreased significantly. The decrease was reversed only after two generation times after the resumption of protein synthesis and was larger in magnitude than that previously observed before division (F. J. Trueba and C. L. Woldringh, J. Bacteriol. 142:869-878, 1980). This decrease in cell diameter correlates with synchronization of cell division which has been shown to occur after amino acid starvation.

Amino Acids↗
PubMed1981

Construction and physical mapping of plasmids containing the MetA gene of Escherichia coli K-12.

Plasmids containing the metA gene of E. coli K-12 were constructed in vitro using pBR322 as the cloning vehicle and lambda metA transducing phage as the source of metA DNA. EcoRI digests of pBR322 and lambda metA20 were joined by ligase and plasmids carrying the metA gene were selected after transformation in a metA deletion strain. Recombinant DNA molecules contained one pBR322 fragment and one lambda metA20 fragment of 12.2 kb which was present in either of two possible orientations. Plasmids constructed by BamHI digestion of lambda metA2 contained a single bacterial DNA fragment of 5.8 kb inserted in the tet gene. Insertion of the metA fragment led to loss of resistance to tetracycline in one orientation and partial resistance in the opposite orientation.

Bacteriophage lambda↗
PubMed1981

Screening for mutants temperature sensitive in protein synthesis by using methionine analogues.

Two new mutants are described which are temperature sensitive in protein synthesis. The mutants were obtained by a screening procedure using methionine analogues. The method is based on two findings: a) that in E. coli, and in other members of the Enterobacteriaceae, sensitivity to methionine analogues increases with the growth temperature, and b) that cells which are not synthesizing proteins during treatment with methionine analogues have a shorter lag in resuming growth subsequent to removal of the analogue.

Escherichia coli↗
PubMed1980

Mapping of virginiamycin S resistance in Bacillus subtilis.

Resistance to virginiamycin S (VS, a type B synergimycin) has been mapped in Bacillus subtilis. Transduction experiments with phage PBS1 indicate that the gene for virginiamycin S resistance (VSR) is cotransduced with the markers pur A16 (20%) and cys A14 (46-49%). Transformation experiments indicate that the gene for virginiamycin S resistance maps between the markers for elongation factor G and erythromycin resistance, and is therefore located within the gene cluster of ribosomal proteins.

Bacillus subtilis↗
PubMed1980

Initiation of deoxyribonucleic acid replication in Escherichia coli B: uncoupling from mass/deoxyribonucleic acid ratio.

In Escherichia coli growing at different rates, the ratio of cell mass to the number of chromosome origins tended to be constant at the time of the initiation of deoxyribonucleic acid (DNA) replication. This observation led to the assumption that the initiation event is controlled in some way by cell mass, e.g., by a growth-dependent synthesis of an initiator or dilution of a repressor. We have now found that the initiation of DNA synthesis can be uncoupled from cell mass. We used a synchronous culture of newly divided cells of E. coli B which was obtained by the membrane elution technique (C.E. Helmstetter, J. Mol. Biol. 24: 417-427, 1967) and was starved for an amino acid. Upon restoration of the amino acid, the cells not only divided at a size that was smaller than normal, but also initiated DNA replication long before they could increase their masses to reach the expected ratio of mass/DNA presumably required for initiation.

Acetates↗
PubMed1980

Development of a multivalent live vaccine active against a wide range of Enterobacteriaceae.

We have constructed a deletion mutant of E. coli which lacks O-antigen - "deep rough". Living bacteria of this strain were injected repeatedly in high numbers into mice and chicks and in all cases were found to be completely harmless. In C3HeB mice, protection was obtained against a wide variety of enteric bacteria and was accompanied by an appreciable increase in titer of antibodies which cross react with LPS extracted from these bacteria. Preliminary experiments indicate that the vaccine provides protection against avian coli pathogens.

Animals↗
PubMed1978

Preferential charging of tRNA-Met-f in Escherichia coli K12.

The charging of tRNA-Met-f and tRNA-Met-m in vivo and in vitro and initiation of polysomes during methionine limitation were studied in two strains of Escherichia coli K12. In the wild-type strain the distribution of polysomes as well as the kinetic parameters of methionyl-tRNA synthetase indicate preferential acylation of tRNA-Met-f. This preferential charging of tRNAM-et-f does not take place in a mutant strain which is also defective in initiation of polysomes during methionine limitation.

Adenosine Triphosphate↗
PubMed1978

Murein biosynthesis during a synchromous cell cycle of Escherichia coli B.

The last stages of murein biosynthesis were studied in relation to the division cycle of Escherichia coli in cells synchronized by amino acid starvation (Ron et al., J. Bacteriol. 123:374--376, 1975). Murein synthesis and the activities of the D-alanine carboxypeptidase and transpeptidase were found to vary significantly during the cell cycle. Maximal synthesis and transpeptidation were observed immediately after cell division, whereas maximal D-alanine carboxypeptidase activity was detected before cell division. These results are in agreement with our earlier findings that before cell division there is a stage of increased hydrolysis of the C-terminal D-alanine moiety of newly synthesized murein strands.

Carboxypeptidases↗
PubMed1976

Translocation in Bacillus subtilis: characterization of elongation factor G by peptidyl-[3H]puromycin synthesis.

This communication describes the characterization of elongation factor G from Bacillus subtilis by the translocation of "native" peptide donors. Translocation was followed by elongation factor G-dependent increase in the synthesis of peptidyl-[3H]puromycin using "washed" ribosomes carrying in vivo-bound peptidyl-transfer ribonucleic acid ("native" peptidyl-transfer ribonucleic acid) molecules as peptide donors. Such ribosomes were obtained from cell extracts by washing at a high salt concentration. The use of "native" peptide donors facilitated the study of translocation under conditions that are closer to the in vivo state than those in the methods previously employed.

Bacillus subtilis↗
PubMed1975

Growth rate of Enterobacteriaceae at elevated temperatures: limitation by methionine.

The effect of elevated temperatures on growth rate was studied in five strains of Enterobacteriaceae. In all the strains tested a shift to the elevated temperature resulted in an immediate decrease in growth rate which was due to limitation in the availability of endogenous methionine. The first biosynthetic enzyme of the methionine pathway-homoserine transsuccinylase-was studied in extracts of Aerobacter aerogenes, Salmonella typhimurium, and Escherichia coli and was shown to be temperature sensitive in all of them.

Acyltransferases↗