Physical study of prophage excision and curing of λ prophage from lysogenic Escherichia coli

Freifelder, David; Kirschner, Ilana; Goldstein, R V; Baran, Nava

doi:10.1016/0022-2836(73)90058-2

Cited by 19 publications

(6 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Freifelder et al (17) and Stevens et al (18) have shown that, in phage lambda, initiation of prophage DNA replication generally precedes excision. Hu et al (19) and Ptashne and Cohen (20) have reported that two copies of the insertion sequence IS1 are present as direct repeats at the junctions of the r-determinant and the RTF-Tc.…”

Section: Methodsmentioning

confidence: 99%

Selective amplification of genes on the R plasmid, NR1, in Proteus mirabilis: an example of the induction of selective gene amplification.

Perlman¹,

Stickgold²

1977

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

The dru-resistance plasmid, NRB, is a 37-,m circular DNA molecule that contains two components: the resistance transfer factor (29 ,unm) carrying the transfer genes and the genes for tetracycline resistance, and the r-determinant (8 Am) carrying the genes for resistance to several other antibiotics including chloramphenicol (Cm) In Proteus mirabifis, these two components are capable of independent replication, or they may replicate as a composite molecule. When cells of P. mirabilis containing NRB are cultured in medium containing Cm at 250 jag/ml a growth lag of 20-35 hr ensues. During this lag, Cm induces the selective amplification of the r-determinant, including the gene for resistance to Cm. The amplification results from the excision of the r-determinant from the R plasmid, the independent replication of the r-determinant to give polymeric as well as monomeric r-determinants, and the eventual reintegration of multiple tandem copies of the r-determinant with the resistance transfer factor to form a new R plasmid with multiple copies of the r-determinant. This mechanism represents a new level of control of gene expression in bacterial systems-namely, the induction of selective gene amplification.The transmissible drug-resistance plasmid NR1 is a polymorphic DNA molecule whose size and density in CsCl have been reported to vary depending on the host strain and culture conditions (refs. 1-4; for a review, see ref. 5). When isolated from strains of Proteus mirabilis, plasmids are found with CsCl buoyant densities of 1.712-1.718 g/ml (6). The 1.712 g/ml plasmid is a composite structure consisting of a 46 X 106 dalton resistance transfer factor (RTF-Tc; 1.710 g/ml) carrying both the tetracycline resistance and transfer genes, linked to a 14 X 106 dalton r-determinant (1.718 g/ml) carrying the genes for resistance to chloramphenicol (Cm), streptomycin, spectinomycin, and sulfonamide (4, 7). This plasmid is called the nonamplified plasmid (N plasmid). The RTF-Tc and r-determinant each contain at least one origin of replication (8). In contrast to the N plasmid, plasmids of higher density contain multiple, tandem copies of the r-determinant and are called amplified plasmids (A plasmids). These polymeric r-determinants can exist either in an autonomous state with a density of 1.718 g/ml or attached to an RTF-Tc to give an enlarged R plasmid (1.716-1.718 g/ml) (4, 7). Cells containing N plasmids and A plasmids are called "N cells" and "A cells," respectively. Clewell et al. (9) have recently described another plasmid that contains multiple copies of a tetracycline-resistance determinant in Streptococcus faecalis.Previous results have shown that, when a population of N

show abstract

Section: Methodsmentioning

confidence: 99%

Selective amplification of genes on the R plasmid, NR1, in Proteus mirabilis: an example of the induction of selective gene amplification.

Perlman¹,

Stickgold²

1977

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…comparison, we studied the sedimentation of folded nucleoids from strains lysogenic for X, before and after induction of the X prophage. Prophage DNA is excised from the host chromosome at 10 to 15 min after induction (5,13). Nucleoids were prepared 18 min after induction, when A DNA comprises 15 to 20% of the total cellular DNA.…”

Section: Resultsmentioning

confidence: 99%

Cellular location of Mu DNA replicas

Pato¹,

Waggoner²

1981

J Virol

View full text Add to dashboard Cite

To ascertain the form and cellular location of the copies of bacteriophage Mu DNA synthesized during lytic development, DNA from an Escherichia coli lysogen was isolated at intervals after induction of the Mu prophage. Host chromosomes were isolated as intact, folded nucleoids, which could be digested with ribonuclease or heated in the presence of sodium dodecyl sulfate to yield intact, unfolded nucleoid DNA. Almost all of the Mu DNA in induced cells was associated with the nucleoids until shortly before cell lysis, even after unfolding of the nucleoid structure. We suggest that the replicas of Mu DNA are integrated into the host chromosomes, possibly by concerted replication-integration events, and are accumulated there until packaged shortly before cell lysis. Nucleoids also were isolated from induced A lysogens and from cells containing plasmid DNA. Most of the plasmid DNA sedimented independently of the unfolded nucleoid DNA, whereas 50% or more of the A DNA from induced lysogens cosedimented with unfolded nucleoid DNA. Possible explanations for the association of extrachromosomal DNA with nucleoid DNA are discussed.

show abstract

“…As there are multiple initiations of prophage replication in situ (203) and the DNA growing points enter the bacterial chromosome from both prophage ends (94,104), A must frequently be excised as a replicating or replicated DNA molecule. This may explain why Freifelder et al (71) rarely recovered A and did not recover F in the CCC form after induction of normal A prophage, but got maximal recovery (almost 100%) of A and F as CCC molecules after the brief induction of a thermally inducible A prophage carrying mutations in the replication genes 0 and P. Therefore, although site-specific recombination is reversible, during excision it seems likely that the prophage is frequently released in a replicative form; the fate of the bacterial chromosome ends is uncertain.…”

Section: Cirularization Of Phage Dnamentioning

confidence: 98%

“…(ii) Via a single reciprocal recombination event between aligned segments at the prophage ends (B * P x P B'), circular phage and chromosome molecules are generated and the original bacterial and prophage sites (attB -B' and attP ., respectively) are restored (71). (iii) The one addition to reversibility is that excision requires not only int (78) but also another phage function, xis (80,112), which is not essential for integration (52).…”

Section: Cirularization Of Phage Dnamentioning

confidence: 99%