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At least 199 records · Page 11Linked to original sources
PubMed1992

[Multi-origin usage for chromosome replication of suppressive integration strain of dnaA46 mutant of Escherichia coli integrated with R6K].

The chromosome of temperature sensitive initiation mutant dnaA46 of Escherichia coli K-12 fails to replicate at 42 degrees C. Suppressive integration (Sin) strain integrated with the R6K plasmid was screened at 42 degrees C. Marker frequency determination of the Sin strain reveals that replication was initiated at the normal site of initiation at 30 degrees C, while at three different sites at 42 degrees C. Two of the sites have been reported in the stable DNA replication mutant, one of them is a novel site. Inhibition of chromosome replication was not observed for the recA derivative of Sin initiated at two of the initiation sites close to the normal initiation site. Inhibition was observed for chromosome replication initiated near the site where chromosome replication normally terminates. It indicates that chromosome replication initiated at sites close to the terminus is recA gene dependent.

Chromosomes, Bacterial↗
PubMed1987

Breakdown and quantitation of the forked termination of replication intermediate of Bacillus subtilis.

Using a procedure that minimizes shear forces, the BamHI-derived forked termination of replication intermediate of Bacillus subtilis, called band I DNA, can be extracted with little or no accompanying band II DNA. It has been shown that band II DNA is a product of band I breakdown. Nuclease P1-mediated breakdown of the forked band I DNA proceeds in two steps. The first causes the release of one of the arms as band II DNA; in the second step, the remaining arm is cleaved away to yield the free stem. It is concluded that band I represents the primary termination of replication intermediate. A quantitative assessment of the level of band I in DNA from cells of the merodiploid strain, GSY1127, growing at different rates has been made. For cells grown in a minimal medium, at least, the experimentally measured level of band I is of the order (approx. 60%) of that predicted for a complete block to movement of the clockwise fork at the replication terminus, terC.

Bacillus subtilis↗
PubMed1997

A binary-BAC system for plant transformation with high-molecular-weight DNA.

A binary-BAC (BIBAC) vector suitable for Agrobacterium-mediated plant transformation with high-molecular-weight DNA was constructed. A BIBAC vector is based on the bacterial artificial chromosome (BAC) library vector and is also a binary vector for Agrobacterium-mediated plant transformation. The BIBAC vector has the minimal origin region of the Escherichia coli F plasmid and the minimal origin of replication of the Agrobacterium rhizogenes Ri plasmid, and thus replicates as a single-copy plasmid in both E. coli and in A. tumefaciens. The T-DNA of the BIBAC vector can be transferred into the plant nuclear genome. As examples, a 30-kb yeast genomic DNA fragment and a 150-kb human genomic DNA fragment were inserted into the BIBAC vector; these constructs were maintained in both E. coli and A. tumefaciens. In order to increase the efficiency of transfer of unusually large BIBAC T-DNAs, helper plasmids that carry additional copies of A. tumefaciens virulence genes virG and virE were constructed. These helper plasmids are compatible with, and can be present in addition to, the BIBAC vector in the A. tumefaciens host. This report details the components of the BIBAC system, providing information essential to the general understanding and the application of this new technology.

Bacterial Proteins↗
PubMed1978

Genetic mapping of the chromosome of Rhizobium trifolii.

Cultures of the wild strain and auxotrophic mutants of Rhizobium trifolii T37 synchronized by means of phenylethanol have been mutagenized with nitrosoguanidine. Fifteen genetic markers were characterized in respect of their order and the time of replication based on the peaks of mutations of the genes. The time of R. trifolii chromosome replication was estimated using inhibitors of the initiation of DNA replication: rifampicin, chloramphenicol and phenylethanol. The replicative map of R. trifolii chromosome has been constructed. Taking into account the replicative map, linkages of the genes, and the bidirectional model of the Rhizobium chromosome replication, a circular genetic map of the chromosome of R. trifolii T37 was elaborated.

Chloramphenicol↗
PubMed1982

Possible involvement of DNA-linked RNA in the initiation of Bacillus subtilis chromosome replication.

After thermal denaturation, an in vivo-labeled RNA was found in a temperature-sensitive initiation mutant of Bacillus subtilis (dna-37) associated with high-molecular-weight DNA. This RNA could be clearly distinguished from other RNA species by different techniques of separation, such as Sepharose 2B filtration, chromatography on nitrocellulose, and equilibrium centrifugation in density gradient. It was obtained even when HCHO was present during denaturation and chilling of nucleic acids and was still detected after a second denaturation as well as after incubation with proteinase K. Properties of the complex were not altered by prior treatment with RNase H. A control experiment using two samples of the complex treated either with pancreatic DNase or with pancreatic RNase, denatured together and centrifuged in the same density gradient, showed that no artifactual associations occur between the DNA and the RNA components of the complex. These results demonstrate that the DNA and RNA in the complex are associated by neither hydrogen bonds nor proteins, but are indicative of a DNA-RNA covalent linkage. In addition, during synchronous replication after a previous period at a nonpermissive temperature, DNA-linked RNA synthesis took place at specific times which coincided with the appearance of rifampin resistance of the first and the second replication cycles. A possible involvement of this RNA in the initiation of chromosome replication is discussed.

Bacillus subtilis↗
PubMed1974

The Bacillus Subtilis genome: replication-order and map-position discrepancies--evidence for a second origin.

Replication order to map position discrepancies have been documented in B. subtilis. The discrepancies were found to occur whenever the genome of B. subtilis was replicated under a variety of physiological conditions and in both 168 and W23 strains. The earliest replicating marker involved in these discrepancies was thr versus purB and aroA versus recA. A detailed linkage analysis of the ura to argA region was consistent with its being a continuous linkage group. This led to the conclusion that an origin for new starts at replication exists between recA and aroA.

Bacillus subtilis↗
PubMed1988

Norfloxacin: a new targeted fluoroquinolone antimicrobial agent.

Norfloxacin is an oral fluoroquinolone antimicrobial agent recently released for the treatment of uncomplicated and complicated urinary tract infections. The drug antagonizes DNA gyrase, an enzyme essential for bacterial DNA replication. Norfloxacin is more potent and broader in spectrum than the earlier developed analogue, nalidixic acid, and is active in vitro against virtually all bacterial pathogens causing urinary tract and gastrointestinal infections, aerobic gram-negative bacilli causing sepsis in neutropenic patients, and Neisseria gonorrhoeae. The drug is administered orally twice daily and achieves high concentrations in urine, stool, renal tissue, and bile. Norfloxacin was at least as effective as currently used agents in treating urinary tract infections, and, in limited studies, bacterial gastroenteritis, gonorrhea, bacterial prostatitis, and prevention of gram-negative bacillary infection in neutropenic patients. Adverse drug effects were mild and included disturbances of the gastrointestinal tract and the central nervous system. Norfloxacin shows promise as an antibacterial agent for genitourinary and gastrointestinal infections.

Animals↗
PubMed2006

The Sinorhizobium meliloti chromosomal origin of replication.

The predicted chromosomal origin of replication (oriC) from the alfalfa symbiont Sinorhizobium meliloti is shown to allow autonomous replication of a normally non-replicating plasmid within S. meliloti cells. This is the first chromosomal replication origin to be experimentally localized in the Rhizobiaceae and its location, adjacent to hemE, is the same as for oriC in Caulobacter crescentus, the only experimentally characterized alphaproteobacterial oriC. Using an electrophoretic mobility shift assay and purified S. meliloti DnaA replication initiation protein, binding sites for DnaA were mapped in the S. meliloti oriC region. Mutations in these sites eliminated autonomous replication. S. meliloti that expressed DnaA from a plasmid lac promoter was observed to form pleomorphic filamentous cells, suggesting that cell division was perturbed. Interestingly, this cell phenotype is reminiscent of differentiated bacteroids found inside plant cells in alfalfa root nodules.

Bacterial Proteins↗
PubMed2003

High-fidelity in vivo replication of DNA base shape mimics without Watson-Crick hydrogen bonds.

We report studies testing the importance of Watson-Crick hydrogen bonding, base-pair geometry, and steric effects during DNA replication in living bacterial cells. Nonpolar DNA base shape mimics of thymine and adenine (abbreviated F and Q, respectively) were introduced into Escherichia coli by insertion into a phage genome followed by transfection of the vector into bacteria. Genetic assays showed that these two base mimics were bypassed with moderate to high efficiency in the cells and with very high efficiency under damage-response (SOS induction) conditions. Under both sets of conditions, the T-shape mimic (F) encoded genetic information in the bacteria as if it were thymine, directing incorporation of adenine opposite it with high fidelity. Similarly, the A mimic (Q) directed incorporation of thymine opposite itself with high fidelity. The data establish that Watson-Crick hydrogen bonding is not necessary for high-fidelity replication of a base pair in vivo. The results suggest that recognition of DNA base shape alone serves as the most powerful determinant of fidelity during transfer of genetic information in a living organism.

Base Pairing↗
PubMed1996

Activation of stable DNA replication in rapidly growing Escherichia coli at the time of entry to stationary phase.

The conditions are described in which DNA replication can occur, in the absence of protein synthesis, in wild-type Escherichia coli cells. Chromosome replication, which is normally inhibited by addition of chloramphenicol, becomes resistant to this drug after nutritional shiftup, e.g. from minimal medium to Luria broth. This replication activity appears transiently when nutritionally upshifted cells enter stationary phase. The activity strictly requires recA+, but it is independent of recB+ and dnaA+. It can occur in the absence of concomitant transcription. Activation of the replication does not result from induction of the SOS response. As the characteristics of this DNA replication resemble those of the previously characterized stable DNA replication, it is termed nutritional shiftup-activatable stable DNA replication, nSDR. Possible mechanisms of the activation of nSDR in rapidly growing cells at the time of entry to stationary phase are discussed.

Bacterial Proteins↗
PubMed1998

An essential protease involved in bacterial cell-cycle control.

Proteolytic inactivation of key regulatory proteins is essential in eukaryotic cell-cycle control. We have identified a protease in the eubacterium Caulobacter crescentus that is indispensable for viability and cell-cycle progression, indicating that proteolysis is also involved in controlling the bacterial cell cycle. Mutants of Caulobacter that lack the ATP-dependent serine protease ClpXP are arrested in the cell cycle before the initiation of chromosome replication and are blocked in the cell division process. ClpXP is composed of two types of polypeptides, the ClpX ATPase and the ClpP peptidase. Site-directed mutagenesis of the catalytically active serine residue of ClpP confirmed that the proteolytic activity of ClpXP is essential. Analysis of mutants lacking ClpX or ClpP revealed that both proteins are required in vivo for the cell-cycle-dependent degradation of the regulatory protein CtrA. CtrA is a member of the response regulator family of two-component signal transduction systems and controls multiple cell-cycle processes in Caulobacter. In particular, CtrA negatively controls DNA replication and our findings suggest that specific degradation of the CtrA protein by the ClpXP protease contributes to G1-to-S transition in this organism.

ATPases Associated with Diverse Cellular Activitie↗
PubMed1976

Direction of deoxyribonucleic acid replication in Escherichia coli under various conditions of cell growth.

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.

Aspartic Acid↗