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At least 55 records · Page 3Linked to original sources
PubMed1975

recA+-dependent inactivation of the lambda repressor in Escherichia coli lysogens by gamma-radiation and by tif expression.

When gamma lysogens of E. coli are induced by gamma-radiation the gamma repressor, as measured by its specific binding to gamma DNA, is rapidly inactivated by a recA+-dependent process which does not require new protein synthesis. This rapid inactivation is similar to inactivation of repressor by expression of the temperature sensitive E. coli mutation tif. In contrast, induction by UV irradiation or mitomycin C treatment requires new protein synthesis and there is a lag before the repressor is inactivated (Tomizawa and Ogawa, 1967; Shinagawa and Itoh, 1973).

Coliphages↗
PubMed1975

The kinetics of derepression of prophage lambda following ultraviolet irradiation of lysogenic cells.

Double lysogens for prophages lambda cI+ and lambda cI ind-ts-857 are induced only by the combined effects of ultraviolet (UV) irradiation and high temperature, not by either treatment alone (Sussman and Jacob, 1962). We have followed the kinetics of inactivation of the cI+ repressor brought about by irradiation in asynchronously and synchronously growing cultures of B/r (lambda cI ind- ts-857). Assays of the yield of phage released as a result of temporary thermal inactivation of the UV-resistant ind- ts-857 repressor at intervals after the irradiation accurately reflect the time course of UV-induced inactivation of the cI+ repressor. The results show that UV-induced derepression takes place in all cells of the population approximately 20 min after the irradiation whether the cells were growing asynchronously or synchronously. Hence UV induction of prophage lambda is not triggered at a particular stage in the cell cycle.

Cell Count↗
PubMed1976

Deletions induced by heat treatment of E. coli K12 lysogenic for lambda prophages.

We have investigated the production of prophage deletions in heat-induced lambda lysogens of E. coli K12. Our results are indicative of a direct action of the heat-induced prophage in producing deletions. The temperature of 40 degrees used for the experiments may be critical to prove this effect. The phage function involved in deletion formation is not known.

Chromosome Aberrations↗
PubMed1977

Five hundredfold overproduction of DNA ligase after induction of a hybrid lambda lysogen constructed in vitro.

A lambda vector that contains the gene for Escherichia coli DNA ligase (lambdagt4-lop-11 lig+) has been modified to achieve overproduction of this enzyme. The third Eco RI site in the lambda chromosome has been altered by mutation, and the left-hand Eco RI fragment has been shortened. The new vector, lambdagt4-lop-11 lig+, forms a stable lysogen which, upon induction, produces a 100-fold increase in DNA ligase activity. Introduction of a phage mutation (S7) that prevents cell lysis results in an even greater increase (500-fold).

Coliphages↗
PubMed1975

Model for the enchancement of lambde-gal integration into partially induced Mu-1 lysogens.

Temperate phage Mu-1, which is able to integrate at random in its host chromosome, is also able to mediate integration of other circular deoxyribonucleic acid, as a lambda-gal mutant unable to integrate by itself. After mixed infection with lambda-gal and Mucplus, galplus transductants are recovered that have the lambda-gal integrated in any circular permutation, sandwiched between two complete Mu genomes in the same orientation, the whole Mu-lambda-gal-Mu structure being found at any location in the bacterial chromosome. Here we show that such a lambda-gal can integrate in an induced Mu lysogen. In this case the lambda-gal is again in any circular permutation, between two Mu in the same orientation, but it is always located at the site of the original Mu prophage, and the two surrounding Mu have always the same genotype as the original Mu prophage. Active Mu replication functions are not essential for that process to occur. This suggests that bacterial replication may generate two Mu copies that in some way can regenerate a Mu attachment site that recombines with the lambda-gal. A model is presented that accounts for these observations, may be helpful for understanding some complex features of Mu development, and may possibly offer a basis for explaining spontaneous duplications.

Chromosomes, Bacterial↗
PubMed1975

Restoration of F' superinfection inhibition in a DnaB mutant of Escherichia coli upon construction of heterozygous DnaB merodiploids or P1 lysogens carrying a dnaB analogue.

F-prime derivatives of the Escherichia coli strain CR34 bearing the thermosensitivity mutation dnaB43 display low levels of plasmid-determined superinfection inhibition in conjugational crosses at 30 C. Salt-mediated phenotypic suppression of this temperature sensitivity fails to restore normal levels of inhibition, indicating its alteration is not a secondary effect of dnaB43 a-tion on growth or deoxyribonucleic acid syntheiss. Superinfection inhibition is fully restored in mutant cells made merodiploid for the dnaB region by introduction of the F' dnaB-+ plasmid F134-1. dnaB43-bearing strains lysogenized with P1 phage contribution dnaB-analogue protein show eight to nine times more superinfection inhibition than do the same cells carrying P1 prophage repressed dnaB-analogue protein production. Taken together, this evidence suggests a direct causal relationship between dnaB43 and the altered superinfection inhibition phenotype.

Coliphages↗
PubMed1976

Bacteriophage-specific DNA-binding proteins in P22-lysogenic and in P22-infected Salmonella typhimurium.

Crude extracts of Salmonella typhimurium lysogenic for phages P22 or L contain proteins that specifically retain phage DNA on nitrocellulose filters. Three DNA-binding activities were found after infection with P22. One is P22 specific, accounts for the largest proportion of DNA-binding proteins, and corresponds most likely to the c2 repressor. An early transient binding activity measured with both P22 and L DNA was found to be directly related to the expression of genes c1 and c3. A third, late binding activity for P22 and L DNA is related to phage production.

DNA, Viral↗
PubMedDate not supplied

[Intracellular growth of actinophage in Actinomyces lividans culture lysogenic heat-induced mutant].

Intracellular growth of a thermoinduced prophage was caused by the action of elevated temperature on the lysogenic culture of Actinomyces lividans 66 (phiC31 ct22). The growth took place in the nucleoid where loose, oval or round, particles consisting of twisted NA threads were formed. Later, electron-dense phage heads, covered with a sheath, appeared, and still later--phage tails. Thermoinduction was terminated by lysis of the mycelium of the actinomycete when mature particles of the actinophage were liberated into a surrounding medium.

Actinomyces↗
PubMedDate not supplied

[Phenomenon of temperate phage restriction and modification in a lysogenic culture of Streptomyces hygroscopicus].

Temperate phages were isolated from the lysogenic culture of Streptomyces hygroscopicus 0485 in the indicator cultures of Str. hygroscopicus 0477 and Str. levoris 1331. The phages were found to be identical in the morphology of particles and serological properties. The phenomenon of cross limitation, by the culture of Str. hygroscopicus 0477, of the phage growing on the culture of Str. levoris 1331, and vice versa, was established. At the same time, the phages were shown to be modified by the host cell.

Bacteriophages↗
PubMed1976

Antigenic changes in Pseudomonas aeruginosa in vivo and after lysogenization in vitro.

Pseudomonas aeruginosa cultures not conforming in antigenic structure to established serogroups were isolated from infants and from infants and from 23 O antigen type strains lysogenized with 22 different phages in vitro. The derivatives, characterized by smooth colonial form and heat stability, retained at least part of the antigens of the parent strains and became agglutinable in certain heterologous sera. All derivatives showed immunoelectrophoretic patterns identical with those of the parent strains. Antigenic analysis showed the presence of factors in the derivatives identical with (italicized figures), bilaterally related to (non-bracketed figures) or unilaterally related to (bracketed figures) O antigens of LANYI's schema: (i) changes in vivo, 01 leads to 01, (O8); O11a, 11b leads to O11a, 11c; (ii) changes in vitro, O1 leads to O1, (O8); O4a, 4b leads to O4a,4b,O1,O8,(O10a), O11; O4a,4b leads to O4a,4b,O1,O8,O10a,O11; O4a,4c leads to O4a,4c,O1,(O8),(O10a),(O11). The antigenic changes were accompanied usually by a loss of sensitivity to several typing phages and the lytic spectrum of phages released from the derivatives had become narrower. The findings suggest that multiple agglutinability of P. aeruginosa frequently encountered in nature is associated with phage action.

Antigens, Bacterial↗
PubMedDate not supplied

[Biological properties of Streptococcus bovis bacteriophages isolated from lysogenic cultures and sheep rumen].

Biological characteristics of eleven phages for Streptococcus bovis were investigated; seven phage were isolated from ovine rumen and four were virulent mutants of temperate phages of lysogenic cultures. The phages had many properties in common: similar morphology of negative colonies, the identical spectrum of lytic action, related antigens, absolute or high requirement of calcium ions, thermolability, and inactivation by the content of the rumen. Their susceptibility to the inactivating action of acetic acid, urea and temperature was however different. Chloroform and phenol may be used during purification and conservation of the phages.

Acetates↗
PubMed1977

Different restriction of bacteriophages T3 and T7 by P1-lysogenic cells and the role of the T3-coded SAMase.

The intracellular growth of the phages T3 and T7 is restricted in the presence of the Escherichia coli prophage P1. Phage T3 has a higher ability to express its genome and to damage the host cell than T7. This partial protection of T3 against P1 restriction is due to the T3-coded SAMase, an enzyme which degrades S-adenosylmethionine, the cofactor of the P1 restriction endonuclease. Since we did not observe DNA cleavage in vivo, we conclude that the in vivo action of the P1 nuclease is limited to a SAM-dependent repressor-like binding to T3 and T7 DNA, while further reactions with the DNA (modification vs cleavage) are blocked.

Coliphages↗