Showing papers on "Escherichia coli published in 1970"
TL;DR: Escherichia coli cells of strain K12 and C can be made competent to take up temperate phage DNA without the use of “helper phage”, and is effective for both linear and circular DNA molecules.
2,580 citations
TL;DR: A new T7-specific RNA polymerase is found in T7 phage-infected cells and provides a direct explanation for the pleiotropic control of late T7 functions exerted by gene I.
Abstract: A new T7-specific RNA polymerase is found in T7 phage-infected cells It is the product of T7 gene I and is physically and biochemically distinct from the host cell RNA polymerase The synthesis of T7 RNA polymerase provides a direct explanation for the pleiotropic control of late T7 functions exerted by gene I
576 citations
TL;DR: The bacterial superoxide dismutase, which catalyzes the disproportionation of univalently reduced oxygen, has now been purified from Escherichia coli and was found to contain manganese.
534 citations
TL;DR: Three types of repairless mutant strains of E. coli were tested for mutability by seven representative mutagens and one strain turned out more mutable than the wild type or nonmutable depending on the repair deficiency and the mutagen.
Abstract: Three types of repairless mutant strains of E. coli were tested for mutability by seven representative mutagens. One strain turned out more mutable than the wild type or nonmutable depending on the repair deficiency and the mutagen. This paper describes a simple method for obtaining information on the mechanism of mutation induction by various mutagens such as environmental ones. [The SCI indicates that this paper has been cited over 230 times since 1970.]
402 citations
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TL;DR: A membrane associated DNA polymerizing enzyme has been solubilized, partially isolated and characterized.
Abstract: A membrane associated DNA polymerizing enzyme has been solubilized, partially isolated and characterized.
397 citations
TL;DR: Replicative synthesis, as distinguished from repair synthesis, occurs at a rate comparable to that observed in vivo; it is dependent on the presence of all four deoxyribonucleoside triphosphates, but does not require exogenous DNA; and it is stimulated by ATP.
Abstract: DNA synthesis has been studied in Escherichia coli cells made permeable to nucleotides by treatment with toluene. Replicative synthesis, as distinguished from repair synthesis, occurs at a rate comparable to that observed in vivo; it is dependent on the presence of all four deoxyribonucleoside triphosphates, but does not require exogenous DNA; and it is stimulated by ATP. Furthermore, replicative synthesis can be abolished at the restrictive temperature in DNA temperature-sensitive mutants. N-ethylmaleimide completely inhibits this type of synthesis, whereas it does not inhibit repair synthesis. Repair synthesis further differs from replicative synthesis in the following points: it does not require ATP; it persists at the restrictive temperature in DNA temperature-sensitive mutants; it can be induced by endogenous or exogenous nuclease activity; and its demonstration requires a Pol+ strain.
304 citations
TL;DR: In this article, it was shown that psoralen cross-links may contribute to the skin photosensitizing action observed for phage λ DNA in vitro and Escherichia coli DNA in intact bacterial cells.
300 citations
TL;DR: The characteristics of a temperature conditional mutant of Escherichia coli K12 indicate that at high temperature, it can complete a DNA cycle already started, but not initiate a new one.
246 citations
TL;DR: The observed distribution of branch separations suggests that there is an excluded volume effect in the renaturation of a population of circularly permuted molecules such that strands with close beginning points preferentially renature with each other.
204 citations
TL;DR: It is concluded that E. coli normally carries a pair of closely-linked genes specifying its minor, or suIII tyrosine tRNA, while the derivative carries a single suIII+ gene.
202 citations
TL;DR: Adenosine-3',5'-cyclic phosphate (cyclic AMP) is absolutely required for flagella formation and, hence, motility in cyclicAMP-deficient mutants of Escherichia coli and Salmonella typhimurium.
Abstract: Adenosine-3′,5′-cyclic phosphate (cyclic AMP) is absolutely required for flagella formation and, hence, motility in cyclic AMP-deficient mutants of Escherichia coli and Salmonella typhimurium.
TL;DR: Transfer factor Tu has been purified to apparent homogeneity from extracts of Escherichia coli and contains a sulfhydryl group essential for GDP binding, which in Tu free of nucleotide reacts readily with N-ethylmaleimide, but in Tu-GDP is almost inert.
TL;DR: The suggestion is made that restoration of recombination by indirect suppression involves an activation or derepression of one or a series of enzymes, which participate in a pathway of recombinations, alternative to the recB and recC pathway, but normally of minor importance.
Abstract: All recB- and recC- mutants of E. coli carry out significant residual genetic recombination, whereas all recA- mutants form no recombinants. This observation suggests that an alternative minor pathway of recombination, independent of recB+ and recC+ products, may be operative in Escherichia coli. Rec+ revertants of recB- recC+, recB+ recC-, and recB- strains of E. coli have been isolated and are shown to fall into at least two major genotypic classes. One class carries revertant mutations which map in or very near the recB and recC genes. In this class an ATP-dependent DNase characteristic of wild type E. coli is restored. The reversions in this class are probably back-mutations or intragenic suppressor mutations. A second class carries revertant mutations which are located far from the recB and recC genes. In this class there is a high level of DNase activity which does not require ATP and is inactive on T4 DNA. Indirect and not informational suppression appears to be responsible for the second class of revertants. The suggestion is made that restoration of recombination by indirect suppression involves an activation or derepression of one or a series of enzymes, which participate in a pathway of recombination, alternative to the recB and recC pathway, but normally of minor importance. The ATP-independent DNase may be one of these enzymes.
TL;DR: An adenosine triphosphate-dependent deoxyribonuclease activity has been detected in lysates of recB(+)recC(+) strains, and mutations in recB or recC lead to loss of this activity, suggesting that these two genes determine the nucleaseActivity.
Abstract: An adenosine triphosphate-dependent deoxyribonuclease activity has been detected in lysates of recB+ recC+ strains. Mutations in recB or recC lead to loss of this activity, suggesting that these two genes determine the nuclease activity. The over-all reaction in crude lysates digests native DNA to nucleoside monophosphates. Complementation between recB21 and recC22 in vivo leads to normal levels of ATP-dependent nuclease activity. No complementation in vitro has been detected. Mutations in a third recombination gene (recA) do not alter significantly the wild-type levels of this nuclease activity.
TL;DR: Independently of the A- and 15-specific restrictions, the growth of phage λ in E. coli 15T- encounters another limitation of yet unknown nature, no such limitation is observed either with phage 82 or with mutants of λ occurring at a frequency of about 10-5.
Abstract: SummaryE. coli 15T- carries two distinct sets of DNA restriction and modification activities. The genetic information for system A is contained in the bacterial chromosome and linked to the thr region. This fact suggests host specificity A to be related to those of strains K and B. The genes controlling system 15 are on a plasmid which is related to phage Pl: it competes with Pl for stable inheritance in the carried state and it genetically recombines with Pl. This recombination may produce plasmid genomes with newly assorted characters (see Table 3). One of them is an active, Pl-like prophage with the 15-specific instead of the parental Pl-specific restriction and modification characters. Superinfection of 15T- with Pl may also result in curing of the bacteria from the restriction plasmid.Bot A- and 15-specific restrictions and modifications act on bacterial DNA, on the DNA of various sex factors and on the DNA of certain bacteriophages, e.g. of phage λ. Phage 82 DNA is sensitive only to 15-specific restriction, but not to A-specific restriction.Independently of the A- and 15-specific restrictions, the growth of phage λ in E. coli 15T- encounters another limitation of yet unknown nature. No such limitation is observed either with phage 82 or with mutants of λ occurring at a frequency of about 10-5.
TL;DR: Temperature-sensitive changes of membrane proteins in a previously described temperature-sensitive DNA synthesis mutant were further examined and indicated that X and Y do not have a precursor-product relation, as suggested by the kinetic studies.
TL;DR: The results of these experiments suggest that the R6 DNA species banding in Proteus is the transfer unit while the species at ϱ = 1.718 g/cm3 contains the drug resistance markers, consistent with a model depicting certain R-factors as being composed of separately replicating, genetically independent units of DNA.
TL;DR: All of the temperature-sensitive mutants of Escherichia coli Kl2 carry mutations in the hsm gene, and it is argued that an hsm-directed polypeptide is required for restriction in addition topolypeptides directed by hssK and hsr.
TL;DR: The desensitization of glycerol kinase to feedback inhibition enhances the power of Glycerol to exert catabolite repression, both on the enzymes of the glycerl system itself and on those of the lactose system, but does not eliminate the phenomenon of diauxic growth in a glucose-glycerol medium.
Abstract: The activity of glycerol kinase is rate-limiting in the metabolism of glycerol by cells of Escherichia coli. A mutant strain producing a glycerol kinase resistant to inhibition by fructose-1,6-diphosphate grows faster than its wild-type parent on glycerol as the sole source of carbon and energy. The amount of intracellular fructose-1,6-diphosphate was determined for wild-type cells growing exponentially on glycerol. The water content of such cells was also determined, allowing calculation of the intracellular concentration of fructose-1,6-diphosphate. This value, 1.7 mm, is adequate to exert substantial inhibition on the wild-type glycerol kinase. The desensitization of glycerol kinase to feedback inhibition also enhances the power of glycerol to exert catabolite repression, both on the enzymes of the glycerol system itself and on those of the lactose system. However, desensitization of glycerol kinase alone does not eliminate the phenomenon of diauxic growth in a glucose-glycerol medium. Biphasic growth in such a medium is abolished if the altered enzyme is produced constitutively. The constitutive production of the mutant kinase at high levels, however, renders the cells vulnerable to glycerol. Thus, when the cells have been grown on a carbon source with a low power for catabolite repression, e.g., succinate, sudden exposure to glycerol leads to overconsumption of the nutrient and cell death.
TL;DR: A new endonuclease activity from Escherichia coli which cleaves circular, single-stranded DNA in the presence of added nucleoside triphosphate has been purified and is therefore implicated in genetic recombination.
Abstract: A new endonuclease activity from Escherichia coli which cleaves circular, single-stranded DNA in the presence of added nucleoside triphosphate has been purified. The activity has not been detected in extracts from certain rec- strains and is therefore implicated in genetic recombination.
TL;DR: Using REP− strains derived by transduction, it is obtained no evidence that three rep mutations confer recombination deficiency, although they do do appear to confer a slight increase in UV sensitivity.
TL;DR: A mutant of Escherichia coli K-12 unable to form an essential component of the enterochelin-dependent iron transport system has been isolated and the cytochrome b(1) and total iron content, and the measurement of the uptake of (55)Fe(3+), indicate an impairment of the enteringochelins-dependentIron transport system.
Abstract: A mutant of Escherichia coli K-12 unable to form an essential component of the enterochelin-dependent iron transport system has been isolated. This strain carries a mutation in a gene designated fep, mapping close to two genes, entA and entD, concerned with enterochelin synthesis. Strain AN102, which carries the fep− allele, accumulates large quantities of enterochelin and gives a growth response to sodium citrate. The cytochrome b1 and total iron content, and the measurement of the uptake of 55Fe3+, indicate an impairment of the enterochelin-dependent iron transport system. The growth response to sodium citrate is related to the presence, in strain AN102, of an inducible citrate-dependent iron transport system.
TL;DR: The purified binding protein when added to cold-shocked E. coli stimulates phosphate uptake in a mutant of E. Escherichia coli with impaired phosphate transport and which also lacks this protein, and does not have any effect on phosphorus uptake in another mutant which has the binding protein but is deficient in phosphate uptake through another lesion.
TL;DR: Evidence based on substrate specificity suggests that this E. coli peptidase is not involved in cleavage of N-terminal methionine from nascent protein chains.
TL;DR: Mutants of Escherichia coli K-12 that grow more slowly in media containing low concentrations of K have been isolated and are therefore referred to as K-dependent, and the abbreviation kdp is proposed for this class of mutant.
Abstract: Mutants of Escherichia coli K-12 that grow more slowly in media containing low concentrations of K have been isolated. All independent mutants of this type which have been studied carry a mutation in a small region of the bacterial chromosome between the supE and gal loci. The growth rate of the mutants is the same as that of the parental strains in medium containing more than 1 mm K, but is only 50% that of the parent when the K concentration is reduced to 0.1 mm. The mutants do not appear to have a primary alteration in K transport, and are therefore referred to as K-dependent. The abbreviation kdp is proposed for this class of mutant.
Journal Article•
TL;DR: It is confirmed that K antigens influence the sensitivity to complement of strains of Escherichia coli and their relation to virulence is discussed.
Abstract: We have confirmed that K antigens influence the sensitivity to complement of strains of Escherichia coli. Resistant strains bound more polycation and by inference therefore had a higher surface negative charge than sensitive strains.
Extracts containing K antigen non-specifically inhibited red cell agglutination and this inhibitory activity was roughly proportional to complement resistance. All of five resistant strains became more sensitive to complement when grown at unusual temperatures and extracts from them then had less inhibitory activity. In four strains of serotype O6 K13 complement resistance was proportional to K antigen content measured by immunodiffusion. However, purified K antigen from a resistant strain (WF82) had much greater agglutination inhibiting activity weight for weight than purified K antigen from a sensitive strain (WF96).
In experiments with 125I-labelled haemolysin K antigens decreased the binding of both IgG and IgM antibodies and also directly reduced complement activity.
The mechanisms of action of K antigens and their relation to virulence are discussed.