Mapping of the chromosome ofMycobacterium phlei by means of mutagenesis of the replication point

1976 ◽  
Vol 21 (1) ◽  
pp. 10-20 ◽  
Author(s):  
M. Koníčková-Radochová ◽  
J. Koníček
Keyword(s):  
Replication Point

scholarly journals The replication of the chromosome of Pseudomonas aeruginosa strain 1: II. Sequential mutagenesis of synchronized cultures

1975 ◽  
Vol 25 (3) ◽  
pp. 215-227 ◽  
Author(s):  
R. J. Booker ◽  
J. S. Loutit
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Bacterial Chromosome ◽  
Linkage Groups ◽  
Gene Frequencies ◽  
Replication Point ◽  
Sequential Mutagenesis ◽  
Exponential Populations ◽  
Synchronized Cultures ◽  
Increased Susceptibility

SUMMARYThe order of replication of a series of genes in Pseudomonas aeruginosa has been studied in synchronized cultures using a method based on the technique of sequential mutagenesis. This technique relies on the increased susceptibility of the replication point of the bacterial chromosome to mutagenesis by N-methyl-N′-nitro-N-nitrosoguanidine. The genes studied were those previously mapped by conjugation and whose order of replication had been studied by an investigation of gene frequencies in exponential populations. The results are consistent with the idea that there is two-way replication of the chromosome of P. aeruginosa starting at a point near trp-1 and arg-6. They also confirm that the two linkage groups which have been found by conjugation replicate at different times. If the assumption is made that there is only one chromosome in P. aeruginosa, the results can be used to show how the two linkage groups may possibly be joined together and the order is such that there would have to be two sites of attachment for the sex factor FP2.

scholarly journals Functional Genomic Analysis of Two Staphylococcus aureus Phages Isolated from the Dairy Environment

2009 ◽  
Vol 75 (24) ◽  
pp. 7663-7673 ◽  
Author(s):  
Pilar García ◽  
Beatriz Martínez ◽  
José María Obeso ◽  
Rob Lavigne ◽  
Rudi Lurz ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Dna Recombination ◽  
Point Mutations ◽  
Genomic Analysis ◽  
Open Reading Frames ◽  
Functional Genomic Analysis ◽  
Replication Point ◽  
Terminal Amino ◽  
Functional Analyses ◽  
Reading Frames

ABSTRACT The genomes of the two lytic mutant Staphylococcus aureus bacteriophages, vB_SauS-phiIPLA35 (phiIPLA35) and vB_SauS-phiIPLA88 (phiIPLA88), isolated from milk have been analyzed. Their genomes are 45,344 bp and 42,526 bp long, respectively, and contain 62 and 61 open reading frames (ORFS). Enzymatic analyses and sequencing revealed that the phiIPLA35 DNA molecule has 3′-protruding cohesive ends (cos) 10 bp long, whereas phiIPLA88 DNA is 4.5% terminally redundant and most likely is packaged by a headful mechanism. N-terminal amino acid sequencing, mass spectrometry, bioinformatic analyses, and functional analyses enabled the assignment of putative functions to 58 gene products, including DNA packaging proteins, morphogenetic proteins, lysis components, and proteins necessary for DNA recombination, modification, and replication. Point mutations in their lysogeny control-associated genes explain their strictly lytic behavior. Muralytic activity associated with other structural components has been detected in virions of both phages. Comparative analysis of phiIPLA35 and phiIPLA88 genome structures shows that they resemble those of φ12 and φ11, respectively, both representatives of large genomic groupings within the S. aureus-infecting phages.

Replication of the bacterial chromosome

1966 ◽  
Vol 164 (995) ◽  
pp. 258-266 ◽  
Keyword(s):  
Escherichia Coli ◽  
Cell Division ◽  
Rapid Growth ◽  
Chromosome Replication ◽  
E Coli ◽  
Initiation Of Replication ◽  
Replication Point ◽  
Generation Times ◽  
Minimal Media ◽  
Resting Period

In this paper I shall confine myself to only one aspect of chromosome replication in bacteria: its control and co-ordination with growth and cell division. The nature of the problem to be considered is made clear by two features of chromosome replication in Escherichia coli , First, under conditions of rapid growth, involving generation times of up to about one hour, DNA synthesis is essentially continuous; there is no detectable resting period corresponding to the G period typically found in higher organisms. Secondly, in glucose minimal media, as the data of Cairns (1963) and others have shown, a single replication point, or growth point, traverses the length of the chromosome during each cycle of replication. It follows that, although the rate of replication in E. coli might be determined by the supply of DNA precursors, the maintenance of the proper sequence of events cannot be controlled in this way since in a system in which DNA synthesis is continuous these precursors must be present at all times. Under the conditions mentioned above in E. coli , for example, the cell must have some means of ensuring that a new cycle of replication is not initiated until the previous one is complete. Consequently the important point of control of replication in bacteria must be over the initiation of replication rather than replication itself.

DENSITY TRANSFER STUDIES OF DNA ISOLATED FROM BACILLUS SUBTILIS AFTER EXPOSURE TO PHENETHYL ALCOHOL

Genetics ◽  
1972 ◽  
Vol 70 (2) ◽  
pp. 215-232
Author(s):  
J Weaver Zyskind ◽  
P A Pattee
Keyword(s):  
Bacillus Subtilis ◽  
Density Gradient ◽  
Fresh Medium ◽  
Weak Point ◽  
Phenethyl Alcohol ◽  
Replication Point ◽  
Cscl Density Gradient ◽  
Subtilis Chromosome ◽  
Light Density ◽  
Density Transfer

ABSTRACT The aim of this study was to determine whether there are specific weak points in the Bacillus subtilis chromosome and if so whether the replication point is the site of breakage. To answer these questions, B. subtilis chromosomes were partially labeled with 5-bromodeoxyuridine (5-BUdR). Sheared or unsheared preparations of partially labeled chromosomes which may or may not contain replication forks were analyzed for the distribution of genetic markers in a CsCl density gradient. Two sets of experiments based upon the density transfer experiments of Yoshikawa and Sueoka (1963) were performed: (1) experiments in which the origin of the chromosome was labeled and (2) experiments in which the terminus of the chromosome was labeled. In the first experiment, strain 23 (thy-, his-) spores were germinated in the presence of 5-BUdR for various lengths of time and then transferred to fresh medium containing phenethyl alcohol (PEA) and thymidine (TdR). The DNA was isolated before and after transfer to PEA and TdR. In the second experiment strain 23 (thy-, his-) spores were germinated in the presence of TdR and then PEA was added. After various lengths of time transfer was made to fresh medium containing PEA and 5-BUdR. The DNA was extracted by an extremely gentle technique to avoid breakage and centrifuged in a CsCl density gradient. PEA was added to the germinated spores to prevent dichotomous replication, but PEA did not prevent dichotomous replication in any of these experiments. This contradicts the conclusion of others that PEA prevents the chromosome from entering a new round of replication, but allows the chromosome to complete the round of replication already begun. The following observations offer support for the hypothesis that the replication point is a weak point in the chromosome: (1) when conditions were created to obtain partially labeled chromosomes with replication points: (a) labeled markers appeared at the hybrid density, (b) unlabeled markers appeared at the light density, (c) shearing of the DNA had little effect on the CsCl density gradient, except on a small proportion of labeled markers which had not appeared at the hybrid density prior to shearing; (2) when conditions were created to obtain partially labeled chromosomes with no replication points: (a) the majority of DNA molecules appeared at an intermediate density between the hybrid and the light densities, (b) the labeled and unlabeled markers appeared in the intermediate peak with approximately the same ratio as in the DNA preparations, (c) the labeled markers were found in the intermediate peak except where dichotomous replication had occurred, (d) after shearing, the labeled markers appeared at the hybrid density and the unlabeled markers appeared at the light density. Thus it is concluded that the replication point is a weak point in the B. subtilis chromosome where breakage easily occurs.

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