Showing papers on "Escherichia coli published in 1972"
TL;DR: Covalently-closed, catenated, and open (nicked) circular forms of R-factor DNA are all effective in transformation, but denaturation and sonication abolish the transforming ability of R.factor DNA in this system.
Abstract: Transformation of E. coli cells treated with CaCl2 to multiple antibiotic resistance by purified R-factor DNA is reported. Drug resistance is expressed in a small fraction of the recipient bacterial population almost immediately after uptake of DNA, but full genetic expression of resistance requires subsequent incubation in drugfree medium before antibiotic challenge. Transformed bacteria acquire a closed circular, transferable DNA species having the resistance, fertility, and sedimentation characteristics of the parent R factor. Covalently-closed, catenated, and open (nicked) circular forms of R-factor DNA are all effective in transformation, but denaturation and sonication abolish the transforming ability of R-factor DNA in this system.
2,907 citations
1,763 citations
TL;DR: The colicinogenic factor E(1) (Col E( 1)) in Escherichia coli continues to replicate by a semiconservative mechanism in the presence of chloramphenicol for 10 to 15 hr, long after chromosomal deoxyribonucleic acid (DNA) synthesis has terminated.
Abstract: The colicinogenic factor E(1) (Col E(1)) in Escherichia coli continues to replicate by a semiconservative mechanism in the presence of chloramphenicol (CAP) for 10 to 15 hr, long after chromosomal deoxyribonucleic acid (DNA) synthesis has terminated. Following CAP addition, the rate of synthesis of plasmid DNA gradually increases to an extent dependent on the medium employed. Within 2 to 4 hr after the addition of CAP, replication in a glucose-Casamino Acids medium approaches a maximum rate representing approximately eight times an average rate which would be required for a net doubling of DNA per cell in one generation. The number of copies of Col E(1) DNA molecules that accumulate under these conditions approaches about 3,000 copies per cell, representing a 125-fold increase over the normal level of 24 copies per cell. The system is particularly convenient for studying the mechanism of DNA replication.
1,094 citations
TL;DR: Use of the infant-mouse test in a study of 37 children with diarrhea in Honolulu revealed no enterotoxin-producing coliform bacteria in the stools, in contrast to studies reported from India, where such strains were found in a large proportion of undifferentiated cases of acute diarrhea in adults.
Abstract: In a new test for detection of Escherichia coli enterotoxin, supernates of broth cultures were injected into the stomachs of infant mice and fluid accumulation in the intestine was measured after 4 hr by weighing. Results with known positive and negative strains were comparable to those obtained with the rabbit-loop test, and the mouse test was easier to perform. Cholera toxin, unlike E. coli enterotoxin, did not dilate infant mouse intestine significantly, even in high concentrations. Use of the infant-mouse test in a study of 37 children with diarrhea in Honolulu revealed no enterotoxin-producing coliform bacteria in the stools. This is in contrast to studies reported from India, where such strains were found in a large proportion of undifferentiated cases of acute diarrhea in adults. None of 15 stock strains of E. coli serotypes generally thought to be enteropathogenic produced significant amounts of enterotoxin as measured by the test in mice.
901 citations
TL;DR: The bacteriostatic properties of milk were abolished if the iron-binding proteins were saturated with iron, and this effect was also abolished by saturating the lactoferrin with iron.
Abstract: Human milk contains large quantities of iron-binding protein, of which the greater proportion is lactoferrin, though small amounts of transferrin are also present. Three samples of human milk with unsaturated iron-binding capacities of between 56 and 89% had a powerful bacteriostatic effect on Escherichia coli O111/B4. The bacteriostatic properties of milk were abolished if the iron-binding proteins were saturated with iron. Purified human lactoferrin, in combination with specific E. coli antibody, strongly inhibited the growth of E. coli, and this effect was also abolished by saturating the lactoferrin with iron.Guinea-pig milk also contains lactoferrin and transferrin. Newly born guinea-pigs fed on an artificial diet and dosed with E. coli O111 had higher counts of E. coli O111 in the intestine than suckled animals. The apparent suppressive effect of guinea-pig milk on E. coli in the intestine could be reversed by feeding the iron compound haematin. It seems that iron-binding proteins in milk may play an important part in resistance to infantile enteritis caused by E. coli.
579 citations
499 citations
TL;DR: The results show that K88 antigen is responsible for attachment of K88-positive bacteria to the wall of the small intestine, and that adhesion is essential for the virulence of K 88- positive bacteria in conventionally reared piglets.
Abstract: The role of the K88 antigen of Escherichia coli in neonatal diarrhea of piglets was studied by comparing a K88-positive strain with three K88-negative strains derived from the K88-positive strain. K88 antigen was produced by the K88-positive strain in the intestinal tract of gnotobiotic piglets, whereas K88-negative strains did not regain the ability to synthesize K88 antigen. Synthesis of the antigen conferred different colonization characteristics on the four strains; K88-positive bacteria adhered to the mucosa of the small intestine, whereas K88-negative bacteria did not attach and were distributed throughout the lumen. Adhesion of K88-positive bacteria to tissue from the small intestine of gnotobiotic piglets was demonstrated in vitro and was inhibited by antisera that contained K88 antibodies. Attachment did not occur with bacteria grown at 18 C. Adhesion of cell-free K88 antigen was also demonstrated. The K88-positive strain and one of the K88-negative strains were equally virulent in gnotobiotic piglets. In contrast, the K88-positive strain killed 50% of conventionally reared piglets, whereas the K88-negative strain killed only 3%. Adhesion of the K88-positive strain, but not of the K88-negative strain, to the mucosa of the small intestine was demonstrated. Our results show that K88 antigen is responsible for attachment of K88-positive bacteria to the wall of the small intestine, and that adhesion is essential for the virulence of K88-positive bacteria in conventionally reared piglets.
445 citations
TL;DR: Of 12 R factors transferred from wild strains of Proteus rettgeri to Escherichia coli K12, all were of the N-compatibility group; three belonged to a newly defined group T, of which Rts1 is the prototype.
Abstract: SUMMARY: Of 12 R factors transferred from wild strains of Proteus rettgeri to Escherichia coli K12, all were fi
- Five were of the N-compatibility group; three belonged to a newly defined group T, of which Rts1 is the prototype; one belonged to group W. The other three constituted at least one compatibility group, not previously described. The replication of two of the T plasmids, like that of Rts1, was temperature sensitive. This set of R factors is significantly different from those derived from bacteria of other genera.
338 citations
TL;DR: Inhibition of protein synthesis in log cultures by the addition of chloramphenicol or amino acid starvation allows ColE1 DNA to continue replicating long after chromosomal replication has ceased.
Abstract: Colicinogenic factor E1 (ColE1) is present in Escherichia coli strain JC411 (ColE1) cells to the extent of about 24 copies per cell. This number does not appear to vary in situations which give rise to twofold differences in the amount of chromosomal deoxyribonucleic acid (DNA) present per cell. If cells are grown in the absence of glucose, approximately 80% of the ColE1 molecules can be isolated as strand-specific DNA-protein relaxation complexes. When glucose is present in the medium, only about 30% of the plasmid molecules can be isolated as relaxation complexes. Medium shift experiments in which glucose was removed from the medium indicate that within 15 min after the shift the majority (>60%) of the plasmid can be isolated as relaxation complex. This rapid shift to the complexed state is accompanied by a two- to threefold increase in the rate of plasmid replication. The burst of replication and the shift to the complexed state are both inhibited by the presence of chloramphenicol. Inhibition of protein synthesis in log cultures by the addition of chloramphenicol or amino acid starvation allows ColE1 DNA to continue replicating long after chromosomal replication has ceased. Under these conditions, noncomplexed plasmid DNA accumulates while the amount of DNA that can be isolated in the complexed state remains constant at the level that existed prior to treatment. In the presence of chloramphenicol, there appears to be a random dissociation and association of ColE1 DNA and “relaxation protein” during or between rounds of replication.
324 citations
323 citations
TL;DR: Three mutations, denoted lex-1, -2 and -3, which increase the sensitivity of Escherichia coli K-12 to ultraviolet light (UV) and ionizing radiation, have been found by three-factor transduction crosses to be closely linked to uvrA on the E. coliK-12 linkage map.
Abstract: Three mutations, denoted lex-1, -2 and -3, which increase the sensitivity of Escherichia coli K-12 to ultraviolet light (UV) and ionizing radiation, have been found by three-factor transduction crosses to be closely linked to uvrA on the E. coli K-12 linkage map. Strains bearing these mutations do not appear to be defective in genetic recombination although in some conjugational crosses they may fail to produce a normal yield of genetic recombinants depending upon the time of mating and the marker selected. The mutagenic activity of UV is decreased in the mutant strains. After irradiation with UV, cultures of the strains degrade their deoxyribonucleic acid at a high rate, similar to recA(-) mutant strains. Stable lex(+)/lec(-) heterozygotes are found to have the mutant radiation-sensitive phenotype of haploid lex(-) strains.
TL;DR: Evidence is presented that E. coli contains a mechanism for selective degradation of abnormal proteins, and finished polypeptides containing puromycin, proteins containing frequent errors in translation, and proteins containing amino-acid analogs were degraded more rapidly than were normal cell proteins.
Abstract: Evidence is presented that E. coli contains a mechanism for selective degradation of abnormal proteins. Unfinished polypeptides containing puromycin, proteins containing frequent errors in translation, such as those synthesized by strains containing a ram mutation or a missense suppressor, and proteins containing amino-acid analogs were degraded more rapidly than were normal cell proteins. The degradation of analog- or puromycin-containing proteins appears to be an energy-dependent process. Unlike normal proteins, such proteins were degraded at similar rates by growing and by nongrowing cells.
TL;DR: Two methods have been used to determine the origin and direction of chromosome replication in Escherichia coli: gradient of marker frequency and sequence of replication in synchronized cultures, and DNA-DNA hybridization was used to assay for gene dosage.
TL;DR: The results suggest that the primary lesion in these double mutants is not in DNA replication per se, and there is extensive DNA degradation.
Abstract: We have isolated a strain of Escherichia coli K-12 carrying a mutation, polA12, that results in the synthesis of a temperature-sensitive deoxyribonucleic acid (DNA) polymerase I. The double mutants polA12 recA56 and polA12 recB21, constructed at 30 C, are inviable at 42 C. About 90% of the cells of both double mutants die after 2 hr of incubation at 42 C. Both double mutants filament at 42 C and show a dependence on high cell density for growth at 30 C. In polA12 recB21 cells at 42 C, DNA and protein synthesis gradually stop in parallel. In polA12 recA56 cells, DNA synthesis continues for at least 1 hr at 42 C, and there is extensive DNA degradation. The results suggest that the primary lesion in these double mutants is not in DNA replication per se.
TL;DR: An RNA methylase activity, absent from resistant strains, is shown here to methylate in vitro the 16S RNA of resistant as well as sensitive strains.
Abstract: Strains of Escherichia coli are resistant to the antibiotic kasugamycin due to the partial non-methylation of 16S ribosomal RNA. An RNA methylase activity, absent from resistant strains, is shown here to methylate in vitro the 16S RNA of resistant as well as sensitive strains.
TL;DR: The ligated ileal loop of rabbits and dogs demonstrates net secretion of fluid and electrolytes in response to intraluminal application of cholera enterotoxin, which indicates that V. cholerae is not the only enteropathogen associated with acute diarrhoea.
Abstract: THE acute diarrhoea of cholera is caused by an enterotoxin produced by Vibrio cholerae1. Experimentally, the activity of this enterotoxin can be demonstrated in the ligated ileal loop of rabbits and dogs2–4. In response to intraluminal application of cholera enterotoxin, these loops demonstrate net secretion of fluid and electrolytes5. V. cholerae, however, is not the only enteropathogen associated with acute diarrhoea. Certain strains of Escherichia coli, an organism usually considered to be normal bowel flora, have been associated with epidemics of acute diarrhoea in infants6, adults7 and a variety of animal species8. Like cholera, E. coli diarrhoea is the result of accidental introduction and colonization of the small intestine by an offending organism capable of producing an enterotoxin7.
TL;DR: Results indicate that the free form of the protein is first synthesized and then converted into the bound form, and it appears that the reaction between the two forms is reversible and that there is a dynamic equilibrium between theTwo forms of theprotein in the envelope.
TL;DR: Ribosomal protein S12, the protein coded by the strA ciatron, was isolated from nine streptomycin-resistant mutants originating from various Escherichia coli strains and analysis of the tryptic peptides revealed that each mutant had a single amino-acid replacement in one of two peptides.
TL;DR: Polynucleotide sequence similarity tests were carried out to determine the extent of divergence present in a number of Escherichia coli strains, obtained from diverse human, animal, and laboratory sources, and closely related strains of Shigella, Salmonella, and the Alkalescens-Dispar group.
Abstract: Polynucleotide sequence similarity tests were carried out to determine the extent of divergence present in a number of Escherichia coli strains, obtained from diverse human, animal, and laboratory sources, and closely related strains of Shigella, Salmonella, and the Alkalescens-Dispar group. At 60 C, relative reassociation of deoxyribonucleic acid (DNA) from the various strains with E. coli K-12 DNA ranged from 100 to 36%, with the highest level of reassociation found for three strains derived from K-12, and the lowest levels for two "atypical" E. coli strains and S. typhimurium. The change in thermal elution midpoint, which indicates the stability of DNA duplexes, ranged from 0.1 to 14.5 C, with thermal stability closely following the reassociation data. Reassociation experiments performed at 75 C, at which temperature only the more closely related DNA species form stable duplexes, gave similar indications of relatedness. At both temperatures, Alkalescens-Dispar strains showed close relatedness to E. coli, supporting the idea that they should be included in the genus Escherichia. Reciprocal binding experiments with E. coli BB, 02A, and K-12 yielded different reassociation values, suggesting that the genomes of these strains are of different size. The BB genome was calculated to be 9% larger than that of K-12, and that of 02A 9% larger than that of BB. Calculation of genome size for a series of E. coli strains yielded values ranging from 2.29 x 10(9) to 2.97 x 10(9) daltons. E. coli strains and closely related organisms were compared by Adansonian analysis for their relatedness to a hypothetical median strain. E. coli 0128a was the most closely related to this median organism. In general, these data compared well with the data from reassociation experiments among E. coli strains. However, anomalous results were obtained in the cases of Shigella flexneri, S. typhimurium, and "atypical" E. coli strains.
TL;DR: Ligated intestine tests in pigs, piglets, calves and lambs indicated that the enterotoxin produced by a group of atypical pig strains of Escherichia coli was probably identical with that produced by enteropathogenic calf and lamb strains.
Abstract: Summary
Ligated intestine tests in pigs, piglets, calves and lambs indicated that the enterotoxin produced by a group of atypical pig strains of Escherichia coli was probably identical with that produced by enteropathogenic calf and lamb strains. It resembled the ST rather than the LT form of the enterotoxin produced by typical pig enteropathogenic strains.
The enterotoxin produced by some of the atypical strains and the calf and lamb strains, like that produced by some typical pig strains, was probably controlled by a transmissible plasmid. So was a K antigen common to many of the calf and lamb strains. Infection experiments indicated that this antigen was important in the pathogenesis of E. coli diarrhoea.
TL;DR: Evidence is presented that the physiological effects of penicillin on E. coli may be due to interaction with at least two specific targets, both of which are enzymes.
Abstract: Evidence is presented that the physiological effects of penicillin on E. coli may be due to interaction with at least two specific targets, both of which are enzymes.
TL;DR: This laboratory demonstrated that the DNA polymerase of the Rauscher leukaemia virus is strongly inhibited in vitro by unprimed, single stranded polyribonucleotides as a result of competition between the polymers and the active template for the same enzyme binding site.
Abstract: A PREVIOUS communication from this laboratory demonstrated that the DNA polymerase of the Rauscher leukaemia virus is strongly inhibited in vitro by unprimed, single stranded polyribonucleotides1 as a result of competition between the polymers and the active template for the same enzyme binding site. This inhibition was apparently specific, since partially purified preparations of DNA polymerase from Escherichia coli and BALB/c mouse embryos were not inhibited in the same conditions. We attempted to determine therefore whether single stranded polyribonucleotides would have any effect on the activities of oncogenic RNA viruses in cultured cells.
TL;DR: It was demonstrated that each of the mutants differ from the wild type by replacement of one amino acid only, and these findings are discussed together with the previous protein-chemical results on another mutant resistant to spectinomycin.
Abstract: SummaryProtein S5 which is known to confer sensitivity to the antibiotic spectinomycin has been isolated from 30S subunits of two spectinomycin-resistant mutants. By comparative amino acid analyses of proteins S5 from wild type and mutant as well as by isolation and analyses of the tryptic peptides it was demonstrated that each of the mutants differ from the wild type by replacement of one amino acid only. As shown by amino acid sequence studies the replacements are located within a very short region of protein S5: Peptide T10 of the wild type (val-ser-lys) is changed to glu-ser-lys in one mutant and to val-pro-lys in the other. These findings are discussed together with our previous protein-chemical results on another mutant resistant to spectinomycin.
TL;DR: It is inferred that Mu-1 can integrate at a very large number of chromosomal sites, which makes it distinct from other known temperate coliphages; the lambdoid phages attach at a particular site, P2 phage attaches at a limited number of sites and P1 resides in the cell as a plasmid6.
Abstract: THE temperate bacteriophage Mu-1 can induce mutations at many different loci in the genome of its host bacterium Escherichia coli K12 (see ref. 1). The mutations are assumed to arise by the insertion of Mu-1 DNA within the affected genes, as the sites of mutations are inseparable from the prophage sites by genetic criteria2, 3. It has been inferred therefore that Mu-1 can integrate at a very large number of chromosomal sites. This attribute of Mu-1 makes it distinct from other known temperate coliphages; the lambdoid phages attach at a particular site4, P2 phage attaches at a limited number of sites5 and P1 resides in the cell as a plasmid6.
TL;DR: A method is described for measuring the rate of phosphoenolpyruvate-dependent phosphotransferase activity for a variety of hexoses in toluene-treated suspensions of Escherichia coli, finding that all strains of E. coli possess at least a low glucose phosphOTransfer enzyme activity under any tested condition of growth.
Abstract: 1. A method is described for measuring the rate of phosphoenolpyruvate-dependent phosphotransferase activity for a variety of hexoses in toluene-treated suspensions of Escherichia coli. 2. The specific activities of the phosphotransferases that catalyse the phosphorylation of hexoses are greatly affected by the carbon source for growth. 3. In all strains of E. coli tested, fructose phosphotransferase activity is induced by growth on fructose. 4. Strains of E. coli differ greatly in the rate at which they phosphorylate glucose, but all strains possess at least a low glucose phosphotransferase activity under any tested condition of growth. Glucose phosphotransferase activity is further induced by growth on glucose; this does not occur in a mutant that lacks the ability to take up methyl α-d-[14C]glucopyranoside and hence grows poorly on glucose. 5. When growing on fructose, two strains of E. coli synthesize the inducible glucose phosphotransferase system gratuitously, and to specific activities higher than observed during growth on glucose. A phosphotransferase catalysing the phosphorylation of mannose is similarly induced.
TL;DR: Results imply that the termini of the restricted DNA have 3'-hydroxyl and 5'-phosphoryl groups, and that they have a duplex structure, however, restricted DNA cannot be phosphorylated by polynucleotide kinase, even after treatment of the DNA with alkaline phosphatase.
TL;DR: Theospholipase activity mainly responsible for phospholipid breakdown was phospholipsase At, and heating at 120 °C at 2.7 kg/cm2, inactivated all phospholIPase activity.
TL;DR: Four new small polypeptides are associated with DNA-dependent RNA polymerase from E. coli after infection with T4 phage, and their molecular weights range from 10,000 to 22,000, as detected by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate.
Abstract: Four new small polypeptides are associated with DNA-dependent RNA polymerase from E. coli after infection with T4 phage. The new polypeptides are easily detected in RNA polymerase from E. coli cells labeled with amino acids after phage infection. Their molecular weights range from 10,000 to 22,000, as detected by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. All four polypeptides are found after infection with either wild-type T4 phage or T4 early amber mutants in genes 44, 42, 47, and 46. None of the polypeptides is labeled significantly before 5 min after infection at 30°. When two maturation-defective amber mutants in gene 55 of T4 phage are used for infection, a polypeptide with a molecular weight of 22,000 is absent. When a maturation-defective amber mutant in gene 33 of T4 phage is used, another small protein is absent.