Showing papers on "Escherichia coli published in 1968"
TL;DR: The amount of tritiated thymidine incorporated into the DNA of irradiated cells indicates that pyrimidine dimers in the DNA inhibit DNA synthesis but are not permanent blocks, and that the daughter-strand DNA synthesized after ultraviolet-irradiation contains gaps, or alkalilabile bonds.
1,043 citations
766 citations
TL;DR: The amino acid phenylalanine is shown to become incorporated intact into lipidic compounds which have been partially characterized and have been examined for their utility with these bacteria.
Abstract: The nature and quantity of the phospholipids of Salmonella typhimurium and Escherichia coli K-12 have been examined. The main classes of phospholipids, phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin have been completely characterized. Four minor compounds have been detected: phosphatidylserine, phosphatidic acid, and two partially characterized lipids. The phospholipid composition of the two organisms is quite similar, the only difference is the absence of one of the minor components and a decreased level of all components in E. coli. A study of the turnover of the phosphate in the phospholipids demonstrated no turnover in phosphatidylethanolamine, a slow turnover in phosphatidylglycerol, and a slow turnover in cardiolipin with, possibly, a transfer of phosphate from phosphatidylglycerol to cardiolipin. The amino acid phenylalanine is shown to become incorporated intact into lipidic compounds which have been partially characterized. Methods for the isolation and separation of lipids have been examined for their utility with these bacteria.
604 citations
429 citations
TL;DR: A factor fraction essential for the in vitro synthesis of RNA bacteriophage Qβ-RNA has been isolated from both infected and uninfected E. coli and indicates that the contribution of the last bacterium to the replication of Q β-RNA is more extensive than was earlier thought.
Abstract: A factor fraction essential for the in vitro synthesis of RNA bacteriophage Qβ-RNA has been isolated from both infected and uninfected E. coli. This indicates that the contribution of the last bacterium to the replication of Qβ-RNA is more extensive than was earlier thought.
360 citations
TL;DR: Colicinogenic factor E1 (Col E1) DNA isolated from Escherichia coli by phenol extraction followed by dye-buoyant centrifugation was found to consist almost exclusively of the monomer 23 s supercoiled circular DNA form.
334 citations
TL;DR: This particulate enzyme catalyzes the terminal cross-linking reaction in cell wall synthesis, a transpeptidation in which a d-alanine residue is lost from the end of one of the N-acetylmuramyl-pentapeptide residues incorporated into the product.
282 citations
280 citations
TL;DR: It is argued that the function of the peptide deformylases is to remove the formyl group from nascent protein, which is quite labile under a variety of experimental conditions and is inhibited strongly by thiols.
274 citations
TL;DR: The complete nucleotide sequence of this tRNA from Escherichia coli has been worked out and it is thought to be the chain-initiating tRNA of protein synthesis in bacterial systems.
Abstract: N-Formyl-methionyl-transfer RNA is thought to be the chain-initiating tRNA of protein synthesis in bacterial systems. The complete nucleotide sequence of this tRNA from Escherichia coli has now been worked out.
266 citations
TL;DR: It is reasoned that addition of penicillin during the period from 0 to 120 min after readdition of amino acids in the presence of lactose ought preferentially to kill RC8sr cells and enrich for relaxed mutants.
Abstract: All previously described mutants showing relaxed control of ribonucleic acid (RNA) synthesis (RCrel strains) have been derived from a common ancestor, Escherichia coli strain W6 (L. Alfoildi, G. S. Stent, and R. C. Clowes, J. Mol. Biol. 5:348, 1962), first described by E. Borek, A. Ryan, and I. Rockenbach (J. Bacteriol. 69:460, 1955). We wish to describe the isolation of independent relaxed mutants and some of their properties. The method of selection was based on the observation (L. Alfoldi et al., Z. Vererbungslehre 94:285, 1963) that, when an RCrel strain was starved of a required amino acid for 200 min in the presence of glucose and subsequently shifted to the appropriate amino acid-supplemented medium with lactose as the sole energy source, these cells experienced a lag of up to 250 min before exponential growth resumed. On the other hand, strains with stringent control (RC8tr) subjected to similar treatment resumed growth after a lag of only 40 to 60 min. We reasoned that addition of penicillin during the period from 0 to 120 min after readdition of amino acids in the presence of lactose ought preferentially to kill RC8sr cells and enrich for relaxed mutants. Reconstruction experiments with mixtures of strain W6 (RCrel) and strain CP78 (RCstr), at a ratio of 1:106, showed this approach to be workable. A derivative of E. coli K-12 W677, strain CP78, F-, RCstr, requiring threonine, leucine, histidine, arginine, and thiamine, was used for the selection of relaxed mutants. It was grown in tris(hydroxymethyl)aminomethane (Tris)-glucose medium (G. Edlin and 0. Maal0e, J. Mol. Biol. 15:428, 1966) supplemented with the requirements mentioned above, treated with ultraviolet (UV) light or nitrous acid, and then subjected to five successive rounds of the selective procedure described above; 21 independent mutants were isolated by this method. Figure la shows the uptake of uracil by the parental RCstr strain in the presence and absence of a required amino acid. Uracil uptake for the mutants appeared to fall into two broad classes: the \"high-relaxed\" mutants synthesize as much
TL;DR: The lysozyme of bacteriophage T4 was purified to apparent homogeneity from lysates of the phage grown on Escherichia coli and was found to have muramidase activity, as egg white lyso enzyme does, when cell walls of Micrococcus lysodeikticus were used as substrate.
TL;DR: Results show the presence of a functional relation between the uvrB and uvrD genes and suggest that the UVRD gene participate in the repair synthesis at a step following that performed by the uVRB gene.
Abstract: SummaryTwenty-four UV sensitive strains which can not carry out the host cell reactivation and two which are deficient in recombination were isolated. By analyzing their properties and genetic locations, 21 UV sensitive strains were classified into the uvrA, B, and C groups and 3 strains into a group which has not been described. Two Rec- strains were classified in the recA group. The UV sensitive mutants of the new group are distinctly different from other mutants in their properties and in the sites of mutation. We named this group the uvrD.These uvrD mutants have the following properties. They have an intermediate sensitivity against UV irradiation and a higher sensitivity against γ-ray irradiation than those of other UV sensitive mutants. The UV damages which are repaired in the participation of the uvrD gene are photoreactivable. In the cells UV irradiated λ phage rapidly loses the susceptibility to photoreactivation during the incubation in broth with chloramphenicol. The DNA of the uvrD mutant is rapidly degraded at a small dose of UV light and to a large extent. The uvrD gene locates very close to the metE gene and uvrD- is dominant over uvrD+. The uvrD cells have the capacity to carry out UV reactivation for UV irradiated λ phage, in contrast to other UV sensitive mutants including the Rec- ones which turned out to have no capacity. A double mutant, uvrB uvrD, is about three times as sensitive as the uvrB mutant against UV irradiation and DNA degradation after UV irradiation takes place at much lower rate than the uvrD mutant. These results show the presence of a functional relation between the uvrB and uvrD genes and suggest that the uvrD gene participate in the repair synthesis at a step following that performed by the uvrB gene.
TL;DR: A method has been developed to select for Escherichia coli mutants which lack certain nucleases, and mutants deficient in endonuclease I or RNase I were essentially identical to wild-type with respect to their general biological properties.
TL;DR: Incubation of purified ribosomes with 32 P-labeled Qβ phage RNA and methionine- 14 C-labeling formylmethionyl-transfer RNA, at low magnesium ion concentrations, followed by zonal centrifugation analysis in sucrose gradients showed that formation of the initiation complex involves at least two steps.
TL;DR: The bacterial recA gene participates in the induction by UV irradiation of the clear mutation of phage λ and the Lac- mutation of bacteria as mentioned in this paper, and acts upon DNA irradiated with UV light.
Abstract: The bacterial recA gene participates in the induction by UV irradiation of the clear mutation of phage λ and the Lac- mutation of bacteria. The necessary function is induced by irradiation of Rec+ bacteria and acts upon DNA irradiated with UV light.
TL;DR: It was concluded that completion of a round of replication is a necessary and sufficient condition of DNA synthesis for cell division.
Abstract: When cultures of Escherichia coli B/r growing at various rates were exposed to ultraviolet light, mitomycin C, or nalidixic acid, deoxyribonucleic acid (DNA) synthesis stopped but cell division continued for at least 20 min. The chromosome configurations in the cells which divided were estimated by determining the rate of DNA synthesis during the division cycle. The cultures were pulse-labeled with 14C-thymidine, and the amount of label incorporated into cells of different ages was found by measuring the radioactivity in cells born subsequent to the labeling period. The cells which divided in the absence of DNA synthesis were those which had completed a round of chromosome replication prior to the treatments. It was concluded that completion of a round of replication is a necessary and sufficient condition of DNA synthesis for cell division.
TL;DR: A method for effective elimination of drug resistance (R) and sex (F) factors in Escherichia coli K-12 strains by treatment with sodium dodecyl sulfate (SDS) is presented and abnormal F(+) cells which retained mating ability but showed resistance to M12 phage were isolated.
Abstract: A method for effective elimination of drug resistance (R) and sex (F) factors in Escherichia coli K-12 strains by treatment with sodium dodecyl sulfate (SDS) is presented. Growth of E. coli harboring R or F factors in Penassay Broth containing SDS led to the loss of all or part of these genetic elements. Appearance of drug-susceptible or F(-) cells among survivors was observed after the culture reached the stationary phase. Drug-susceptible cells which had lost all of their resistance markers by SDS treatment could be efficiently infected with R or F factors. Among isolated segregants which came from resistant cells, tetracycline-susceptible cells were the major segregant class. Drug-susceptible cells gave no revertants to drug resistance. By treatment of F(+) cells with SDS, unusual F(+) cells which retained mating ability but showed resistance to M12 phage were also isolated, together with mutants of another type which lost mating ability but retained sensitivity to M12 phage. Since SDS is more toxic to R(+) cells than R(-) cells, the isolation of drug-susceptible or F(-) cells under these conditions may be partly attributable to selective growth of drug-susceptible or F(-) cells in SDS-Penassay Broth.
TL;DR: This activity renders the unmodified replicative form of phage fd resistant to B-specific restriction and is only present in strains carrying intact genes for type B modification.
Abstract: An enzymatic activity, having the properties expected of a B-specific host-controlled modification enzyme, has been purified from an extract of Escherichia coli strain B. This activity renders the unmodified replicative form of phage fd resistant to B-specific restriction and is only present in strains carrying intact genes for type B modification. In phosphate buffer, the enzyme acts optimally at pH 6 and is dependent upon a single cofactor, S-adenosylmethionine.
TL;DR: An acid-degradation product, S-methylamino-methyluracil, has been synthesized and is identical to that derived from the natural product.
Abstract: Two new sulfur-containing pyrimidine nucleotides have been isolated from hydrolyzates of Escherichia coli transfer RNA. The structures, 2-thiocytosine and 5-methylaminomethyl-2-thiouracil, have been assigned to the bases as a result of study of ultraviolet and mass spectra. An acid-degradation product, S-methylamino-methyluracil, has been synthesized and is identical to that derived from the natural product.
TL;DR: The theoretical expectation for the relation between the temporal changes in the molecular weight distribution of radioactively labeled RNA and the rate of RNA chain-growth has been calculated and is determined to be 55 nucleotides per second at 37 °C.
TL;DR: Proteins made by E. coli cells infected with bacteriophage T4 were analyzed by a method which combined disc electrophoresis and autoradiography, showing that the early proteins are not controlled as a single homogeneous class all members of which are synthesized during the same time periods.
TL;DR: The E. coli and S. aureus enzymes have been compared and it is concluded that they are identical with respect to molecular weight and pH optimum, but differ withrespect to heat stability, substrate affinity, electrophoretic mobility, and immunological reactivity.
Abstract: Chloramphenicol-resistant strains of Staphylococcus aureus contain an inducible enzyme which inactivates chloramphenicol by acetylation in the presence of acetyl coenzyme A. The products of acetylation are chromatographically indistinguishable from those obtained with chloramphenicol-resistant Escherichia coli harboring an R factor. The kinetics of induction of chloramphenicol acetyltransferase are complicated by the inducer's effect on protein biosynthesis and its fate as chloramphenicol 3-acetate, which is not an inducer of the enzyme. The E. coli and S. aureus enzymes have been compared, with the conclusion that they are identical with respect to molecular weight (approximately 78,000) and pH optimum (7.8), but differ with respect to heat stability, substrate affinity, electrophoretic mobility, and immunological reactivity. Antiserum prepared against enzyme from E. coli contains precipitating antibody, which inactivates the E. coli enzyme, but neither precipitates nor neutralizes the activity of S. aureus enzyme.
TL;DR: Evidence is presented that the degradation of newly synthesized T4 DNA which occurs in infected cells lacking the phage-directed dCTPase occurs in two similar stages; in such cells cytosine is substituted extensively for the hydroxymethylcytosine normally found in T4 phage DNA.
TL;DR: Host DNA synthesis does not stop when chloramphenicol is present before and during the infection, which indicates that a phage-specific protein is responsible for the cessation of host DNA synthesis.
TL;DR: The l -α-glycerophosphate system is a regulon under negative control, which does not have to be further catabolized for its inducer activity.
TL;DR: Fourteen mutant strains of Escherichia coli were examined, each of which requires tryptophan for growth but is unaltered in any of the genes of the tryPTophan biosynthetic operon, and it is found that several of the mutants produce tryptophileanyl-tRNA synthetases which are more heat-labile than the enzyme of the parental wild-type strain.
Abstract: Fourteen mutant strains of Escherichia coli were examined, each of which requires tryptophan for growth but is unaltered in any of the genes of the tryptophan biosynthetic operon. The genetic lesions responsible for tryptophan auxotrophy in these strains map between str and malA. Extracts of these strains have little or no ability to charge transfer ribonucleic acid (tRNA) with tryptophan. We found that several of the mutants produce tryptophanyl-tRNA synthetases which are more heat-labile than the enzyme of the parental wild-type strain. Of these heat-labile synthetases, at least one is protected against thermal inactivation by tryptophan, magnesium, and adenosine triphosphate. Two other labile synthetases which are not noticeably protected against heat inactivation by substrate have decreased affinity for tryptophan. On low levels of supplied tryptophan, these mutants exhibit markedly decreased growth rates but do not contain derepressed levels of the tryptophan biosynthetic enzymes. This suggests that the charging of tryptophan-specific tRNA is not involved in repression, a conclusion which is further substantiated by our finding that 5-methyltryptophan, a compound which represses the tryptophan operon, is not attached to tRNA by the tryptophanyl-tRNA synthetase of E. coli.