Weigle reactivation of diploid M13 phage

Summary The limited ability of ultraviolet (UV)-irradiated E. coli cells to W-reactivate UV-irradiated, single-stranded DNA phages fd and M13 was investigated. The kinetics of induction for W-reactivation of UV-irradiated fd phage are different from that for other SOS functions. W-reactivation of UV-irradiated M13 phage was studied using phage particles that contain at least two single-stranded DNA genomes. No effect on the extent of W-reactivation of diploid phage was observed, compared to that of normal haploid phage, indicating that the mechanism of W-reactivation of single-stranded DNA phages does not involve recombination between partially replicated genomes.     

Weigle reactivation of diploid M13 phage

Molecular Genetics and Genomics - The limited ability of ultraviolet (UV)-irradiated E. coli cells to W-reactivate UV-irradiated, single-stranded DNA phages fd and M13 was investigated. The...     

Weigle reactivation of the single-stranded DNA phage f1

Summary The survival of ultraviolet light (UV) damaged single-stranded DNA bacteriophage f1 is increased when the Escherichia coli host is irradiated with UV prior to infection. This repair, called Weigle reactivation, is multiplicity independent and is absent in recA and in lexA mutants. The function of the recA-lexA repair system needed is repair and not recombination, as demonstrated by the absence of Weigle reactivation in mutants that are recombination proficient but defective in repair of double-stranded DNA. Weigle reactivation of f1 requires high levels of the recA protein, and in addition activation of recA or another protein. This activation can be produced by UV irradiation, or by the tif-1 allele of recA together with the spr allele of lexA. Mutagenesis of f1 has the same requirements as W-reactivation, and in addition requires UV irradiation of the phage.     

Repressor defective mutants, virulent mutants and adsorption resistance of lysogenic cells in case of phage kappa of Serration

Summary Thermoconditional clearplaque mutants (c_t) of phage have been isolated, which as prophages can be induced by exposure of the 30°C-grown lysogenic bacteria to 42°C. The thermoinduction of the lysogenic cells needs protein synthesis as shown by the inhibitory effect of chloramphenicol. The c_t-mutations are located in clearplaque region III of the genetic map of . Thus this region contains information for the prophage repressor.-lysogenic cells are adsorption resistant against -phages except the cells with mutant prophages of clearplaque region I (l_I mutants). Virulent (v) mutants which can grow in l_I-lysogenic cells appear after direct plating of extracellularly uv irradiated phage with l_I-lysogenic indicator bacteria. Surprisingly all these mutants show a more or less reduced plaque forming ability at 37°C compared with 30°C. For one of the v-mutants the maximum thermosensitive phase in the latent period was checked and found to be very shortly before lysis.     

Weigle reactivation and mutagenesis of bacteriophage lambda in lexA(Def) mutants of E. coli K12

Summary The SOS response in UV-irradiated bacteria enhances the survival and mutagenesis of infecting damaged bacteriophage . In a lexA(Def) strain, SOS bacterial genes are fully derepressed by an inactivating mutation in the LexA repressor gene. We tested several lexA(Def) derivative strains for their capacity to constitutively promote high survival and mutagenesis of irradiated . We showed that UV irradiation of the lexA(Def) host bacteria is still necessary for optimal efficiency of both these SOS functions, which are dependent on the umuC gene product and an activated form of RecA protein.     

Inducible reactivation of UV-irradiated cholera phage e5 in Vibrio cholerae MAK757

Summary The survival of UV-irradiated cholera phage e5 was found to increase when the host cells, Vibrio cholerae MAK757, were exposed to a low dose of UV irradiation before phage infection (Weigle reactivation), indicating the existence of a UV-inducible DNA repair pathway (SOS repair) in V. cholerae MAK757. The induction signal generated by UV irradiation was transient in nature and lasted about 20–30 min at 37°C. Maximal weigle reactivation of the phage was obtained when the host cells were irradiated with a UV dose of 16 J/m². V. cholerae MAK757 was also found to possess efficient photoreactivation and host cell reactivation of UV-damaged DNA in phage e5.     

Mutagenesis of ultraviolet-irradiated lambda phage by host cell irradiation: induction of Weigle mutagenesis is not an all-or-none process

Summary Ultraviolet mutagenesis of lambda phage to clear plaque formers is the same in the total phage population and in subpopulations of phage which have also mutated to gam ^- or at an amber codon. This is true for phage assayed in host cells in which Weigle mutagenesis has been either partially induced by low levels of ultraviolet irradiation, or fully induced by higher levels. If induction of Weigle mutagenesis were all-or-none, clear plaque formers in phage subpopulations selected for another mutation elsewhere would come mainly from induced cells; then the clear plaque mutation rate would always be that for fully induced host cells. Therefore, induction requires more than one lesion in host cell DNA.Although thymine starvation of cells induces synthesis of recA protein, it does not induce Weigle mutagenesis; in fact starvation inhibits induction of this process on subsequent ultraviolet irradiation of the cells.     

Mutagenesis of lambda phage: Weigle mutagenesis is induced by coincident lesions in the double helical DNA of the host cell genome

Summary We have studied the increase in mutation in mutagenized lambda phage when the host cells are also irradiated with ultraviolet light, Weigle mutagenesis. The increase in mutation is induced mainly by coincidences between a radiation-produced lesion in one strand of the host cell DNA and a second lesion in the complementary strand. This conclusion is based on experiments in which incorporation of the base analog bromouracil sensitized the host cells to ultraviolet light. For the same number of bromouracils incorporated per cell, uniform substitution gave a higher level of Weigle mutagenesis than did substitution in only one strand of the DNA double helix. The data also show some induction of Weigle mutagenesis by processes linear in ultraviolet fluence; possibilities include: lesions involving both complementary strands such as crosslinks, lesions in one strand opposite pre-existing discontinuities in the complementary strand, and very small contributions to induction from lesions in one strand only of the DNA.     

Growth and phage production of lysogenic B. megatherium

Cell multiplication and phage formation of lysogenic B. megatherium cultures have been determined under various conditions and in various culture media. 1. In general, the more rapid the growth of the culture, the more phage is produced. No conditions or culture media could be found which resulted in phage production without cell growth. 2. Cultures which produce phage grow normally, provided they are shaken. If they are allowed to stand, those which are producing phage undergo lysis. Less phage is produced by these cultures than by the ones which continue to grow. 3. Cells plated from such phage-producing cultures in liquid yeast extract medium grow normally on veal infusion broth agar or tryptose phosphate broth agar, which does not support phage formation, but will not grow on yeast extract agar. 4. Any amino acid except glycine, tyrosine, valine, leucine, and lysine can serve as a nitrogen source. Aspartic acid gives the most rapid cell growth. 5. The ribose nucleic acid content is higher in those cells which produce phage. 6. The organism requires higher concentrations of Mg, Ca, Sr, or Mn to produce phage than for growth. 7. The lysogenic culture can be grown indefinitely in media containing high phosphate concentrations. No phage is produced under these conditions, but the cells produce phage again in a short time after the addition of Mg. The potential ability to produce phage, therefore, is transmitted through cell division. 8. Colonies developed from spores which have been heated to 100°C. for 5 minutes produce phage and hence, infected cells must divide. 9. No phage can be detected after lysis of the cells by lysozyme.     

T 4 -mediated v-gene reactivation of UV-irradiated phage Ti, and its comparison with host-cell reactivation

Soaked seeds of Vicia faba were irradiated with 800 or 400 R, or two 400-R exposures, both with VAC (vacuum) but one with a concomitant treatment of CHM (cycloheximide) (I μg/ml). The chromosome aberration yields from each regimen varied with fixation time such that a unique and characteristic aberration yield for each regimen relative to the others was not obtained. Were single fixations employed one could obtain yields which would indicate no, some, or maximum repair. A single fixation would lead to an incorrect estimation of chromosome damage repair.     

The linear double-stranded DNA of phage Bam35 enters lysogenic host cells, but the late phage functions are suppressed

Bam35, a temperate double-stranded DNA bacteriophage with a 15-kb linear genome, infects gram-positive Bacillus thuringiensis cells. Bam35 morphology and genome organization resemble those of PRD1, a lytic phage infecting gram-negative bacteria. Bam35 and PRD1 have an outer protein coat surrounding a membrane that encloses the viral DNA. We used electrochemical methods to investigate physiological changes of the lysogenic and nonlysogenic hosts during Bam35 DNA entry and host cell lysis. During viral DNA entry, there was an early temporal decrease of membrane voltage associated with K+ efflux that took place when either lysogenic or nonlysogenic hosts were infected. Approximately 40 min postinfection, a second strong K+ efflux was registered that was proposed to be associated with the insertion of holin molecules into the plasma membrane. This phenomenon occurred only when nonlysogenic cells were infected. Lysogenic hosts rarely were observed entering the lytic cycle as demonstrated by thin-section electron microscopy.