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Determination of deoxyribonucleic acid replication time in exponentially growing Escherichia coli B/r. 下载免费PDF全文
The time necessary to replicate the chromosome (C period) was measured in Escherichia coli B/r (ATCC 12407) and a low-thymine-requiring derivative of that strain. In the Thy- strain, C was measured as a function of growth rate and exogenous thymine concentration either from step-up or chloramphenicol experiments. In the Thy+ parental strain, C was measured only as a function of the growth rate and only by the chloramphenicol method. The C period was found to decrease with growth rate and, in the Thy- strain, the C period also decreased with increasing thymine concentration. It approached a value of approximately 37 min at high growth rates. 相似文献
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Initiation of DNA replication in Escherichia coli. 总被引:4,自引:1,他引:3
W Messer 《Journal of bacteriology》1987,169(8):3395-3399
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Membrane-bound deoxyribonucleic acid from Escherichia coli: effects of replication, protein synthesis, and ribonucleic acid synthesis. 下载免费PDF全文
The experiments presented in this paper suggest that the shift observed in sedimentation of deoxyribonucleic acid from cells of Escherichia coli subjected to amino acid starvation is related to inhibition of ribonucleic acid synthesis rather than to its release from the membrane at the termination of replication. 相似文献
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Accumulation of the capacity of initiation of deoxyribonucleic acid replication in Escherichia coli. 总被引:2,自引:7,他引:2 下载免费PDF全文
Several temperature-sensitive initiation mutants of Escherichia coli were examined for the ability to initiate more than one round of replication after being held at nonpermissive temperature for approximately 1.5 generation equivalents. The capacity for initiation was measured by residual synthesis experiments and rate experiments under conditions where protein synthesis and ribonucleic acid synthesis were inhibited. Results of the rate and density transfer experiments suggest that the cells may initiate more than one round of replication in the absence of protein or ribonucleic acid synthesis. This contrasts with the results of the residual synthesis experiments which suggest that, under these conditions, only one round of synthesis is achieved. These findings suggest that the total amount of residual synthesis achieved in the presence of an inhibitor may be both a function of the number of initiation events which occur and the effect of the inhibitor of protein or ribonucleic acid synthesis on chain elongation. 相似文献
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Chromosome structure of Escherichia coli mutants temperature sensitive for deoxyribonucleic acid replication. 下载免费PDF全文
Folded chromosomes were isolated from Eschericia coli thermosensitive dnaA initiation mutants incubated at the nonpermissive temperature and were analyzed by neutral sucrose density gradient centrifugation. A chromosomal structure that sedimented at approximately 1,500S accumulated when the dnaA gene product was inactive. When the cells were returned to a permissive temperature, the folded chromosomes exhibited a decrease in sedimentation velocity to 1,300S but still retained their uniform structure. Very little deoxyribonucleic acid synthesis occurred during the period in which the chromosomes exhibited the reduction in sedimentation velocity. A dnaG elongation mutant showed no unique chromosome structure when the dnaG gene product was inactive. 相似文献
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Initiation of chromosome replication in dnaA and dnaC mutants of Escherichia coli B/r F. 总被引:10,自引:6,他引:4 下载免费PDF全文
Regulatory aspects of chromosome replication were investigated in dnaA5 and dnaC2 mutants of the Escherichia coli B/r F. When cultures growing at 25 degrees C were shifted to 41 degrees C for extended periods and then returned to 25 degrees C, the subsequent synchronous initiations of chromosome replication were spaced at fixed intervals. When chloramphenicol was added coincident with the temperature downshift, the extend of chromosome replication in the dnaA mutant was greater than that in the dnaC mutant, but the time intervals between initiations were the same in both mutants. Furthermore, the time interval between the first two initiation events was unaffected by alterations in the rate of rifampin-sensitive RNA synthesis or cell mass increase. In the dnaC2 mutant, the capacities for both initiations were achieved in the absence of extensive DNA replication at 25 degrees C as long as protein synthesis was permitted, but the cells did not progress toward the second initiation at 25 degrees C when both protein synthesis and DNA replication were prevented. Cells of the dnaA5 mutant did not achieve the capacity for the second initiation event in the absence of extensive chromosome replication, although delayed initiation may have taken place. A plausible hypothesis to explain the data is that the minimum interval is determined by the time required for formation of a supercoiled, membrane-attached structure in the vicinity of oriC which is required for initiation of DNA synthesis. 相似文献
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Characteristics of cold-sensitive mutants of Escherichia coli K-12 defective in deoxyribonucleic acid replication. 总被引:1,自引:5,他引:1 下载免费PDF全文
Four cold-sensitive mutants of Escherichia coli have been isolated which show a reduced ability to synthesize deoxyribonucleic acid at low temperature. The mutants also have a reduced ability to incorporate nucleoside triphosphates into deoxyribonucleic acid at low temperature in cell preparations made permeable with toluene. All four mutations are located at or near the dnaA locus on the E. coli genetic map. They are recessive to the wild-type allele and two of them can be integratively suppressed by F episomes. 相似文献
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Stimulation of deoxyribonucleic acid replication fork movement by spermidine analogs in polyamine-deficient Escherichia coli. 总被引:6,自引:2,他引:4 下载免费PDF全文
We examined the rate of deoxyribonucleic acid (DNA) replication fork movement in polyamine-deficient cells of Escherichia coli by two independent techniques. DNA autoradiography was used to directly visualize the length of DNA produced during a given time interval, and replication rates were calculated. The amount of DNA synthesized after blocking protein synthesis also allowed calculation of replication rates. We found that the DNA chain elongation rate in polyamine-deficient cells was about half that of putrescine- or spermidine-supplemented cells. We also found that spermidine homologs of increasing chain length, when present at equal intracellular concentrations, exhibited a decreasing ability to support growth and the rate of DNA replication fork movement. The kinetics of recovery of DNA synthesis from the polyamine-deficient state were also investigated. A new rate of DNA synthesis was reached about 20 min after addition of spermidine to polyamine-limited cells. The rise in the rate of DNA synthesis was preceded by a rise in the intracellular concentration of spermidine. 相似文献
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Direction of deoxyribonucleic acid replication in Escherichia coli under various conditions of cell growth. 总被引:4,自引:4,他引:0 下载免费PDF全文
The direction of chromosome replication in a temperature-sensitive initiation mutant of Escherichia coli (CT28) is shown autoradiographically to be bidirectional. This mode of replication persists even when the rate of replication is reduced by slow growth in succinate minimal medium or in the presence of chloramphenicol. Therefore, although the rate of replication can be affected by certain physiological stimuli, the topology of replication need not be. 相似文献
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Genetic and physiological characterization of a spontaneous mutant of Escherichia coli B/r with aberrant control of deoxyribonucleic acid replication. 总被引:1,自引:1,他引:0 下载免费PDF全文
Strain TJK16, a low-thymine-requiring thyA deoB derivative of Escherichia coli B/r A, was found to have an increased initiation mass due to a mutation in a gene affecting the control of initiation of deoxyribonucleic acid replication. In contrast to temperature-sensitive initiation mutants, initiation in TJK16 was not temperature sensitive. By phage P1 transduction, it was found that the mutation lies within a small region of the chromosome between dnaA and gyrB; this region includes dnaN and recF. Coumermycin-resistant derivatives of B/r and TJK16 had the same initiation mass as their coumermycin-sensitive parents, and TJK16 had the same sensitivity to coumermycin as the B/r parent, suggesting that the initiation mutation is not in gyrB. 相似文献
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Isolation and characterization of thermosensitive Escherichia coli mutants defective in deoxyribonucleic acid replication 总被引:16,自引:14,他引:16
J A Wechsler V Nüsslein B Otto A Klein F Bonhoeffer R Herrmann L Gloger H Schaller 《Journal of bacteriology》1973,113(3):1381-1388
Thermosensitive deoxyribonucleic acid replication-defective mutants have been isolated by using an autoradiographic selection method. The mutants have been analyzed genetically and biochemically. Some of the mutants show thermosensitivity of in vitro deoxyribonucleic acid replication. These can be classified into three groups according to their behavior in in vitro complementation assays. This classification is congruent with that obtained by genetic mapping by using cotransduction frequencies with selected markers in P1 transduction analysis. 相似文献
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Initiation of deoxyribonucleic acid replication in a temperature-sensitive mutant of B. subtilis: evidence for a transcriptional step 总被引:3,自引:8,他引:3
S J Laurent 《Journal of bacteriology》1973,116(1):141-145
A mutant of Bacillus subtilis unable to initiate a new round of replication at 45 C has been described. Here we show that inhibition of DNA synthesis in this mutant is reversible and that DNA synthesis is resumed at low temperature, even in the presence of chloramphenicol. Initiation of a new replication cycle thus can occur in the absence of protein synthesis. A thermolabile component required for initiation therefore appears to be synthesized at 45 C in an inactive form and can be activated at 30 C in the presence of an inhibitor of protein synthesis. Although resistant to chloramphenicol, the reinitiation of replication occurring after lowering the temperature is sensitive to rifampin and streptolydigin. 相似文献
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