Class of {varphi}X174 Mutants Relatively Deficient in Synthesis of Viral RNA

Nonpermissive cells infected with {varphi}X174 gene D amber mutants synthesized some sixfold less viral RNA than permissive cells. The decrease was unaffected by increasing the multiplicity of infection and was a consequence of an overall decrease in all viral RNA species. It is suggested that the gene D product may function in replicative form DNA unwinding to expose the template for transcription

The Process of Infection with Bacteriophage øX174 XIII. Evidence for an Essential Bacterial "Site"

The burst of a starved bacterium infected with several øX174 bacteriophage was usually found to contain genetic traits of only one of the possible parents; less often, two phage multiplied in the same host cell. Unstarved cells, in contrast, supported the growth of at least four parental phage types. The unproductive phage seemed to be able to undergo the intracellular transition from parental single-stranded deoxyribonucleic acid to the double-stranded "replicative form" (RF). These results are taken to mean that some bacterial factor required for a step between RF synthesis and maturation of progeny is limited in starved cells

The process of infection with bacteriophage phiX174, XXX. Replication of double-stranded phiX DNA

Intermediates involved in the replication of double-stranded phiX174 RF DNA have been identified and partially characterized. Analysis of pulse-labeled RF DNA suggests that the synthesis of progeny RF molecules involves, in part, the addition of nucleotides to linear complementary strands on a circular parental strand as template, so as to produce intermediate DNA strands of greater than viral length. Electron microscopy reveals DNA rings with "tails" and "double rings," which could be the intermediate structures. A model is postulated for the replication process

Recombinant DNA Molecules of Bacteriophage phi X174

phi X174 DNA structures containing two different parental genomes were detected genetically and examined by electron microscopy. These structures consisted of two monomeric double-stranded DNA molecules linked in a figure 8 configuration. Such DNA structures were observed to be formed preferentially in host recA+ cells or recA+ cell-free systems. Since the host recA+ allele is required for most phi X174 recombinant formation, we conclude that the observed figure 8 molecules are intermediates in, or end products of, a phi X174 recombination event. We propose that recombinant figure 8 DNA molecules arise as a result of "single-strand aggression," are stabilized by double-strand "branch migration," and represent a specific example of a common intermediate in genetic recombination

Deletion mutants of bacteriophage phiX174

Mutants of bacteriophage phiX174 have been isolated that are less dense than wild-type phiX particles in CsCl. When mutant viral (+) strand DNA and wild-type complementary (-) strand DNA are hybridized, the resulting duplex molecules have single-stranded loops characteristic of wild-type-deletion heteroduplexes. The mutant bacteriophages fail to complement phiX amber mutants in cistron E. We conclude that the mutant viruses have deleted approximately 7% of the phiX genome in the region of cistron E

Genetic Recombination in Bacteriophage {varphi}X174

Genetic recombination in bacteriophage {varphi}X174 usually takes place early in the infection process and involves two parental replicative form (double-stranded) DNA molecules. The host recA protein is required; none of the nine known {varphi}X174 cistron products is essential. The products of a single recombination event are nonreciprocal and asymmetric. Typically, only one of the parental genotypes and one recombinant genotype are recovered from a single cell. An alternative, less efficient recombination mechanism which requires an active {varphi}X174 cistron A protein is observed in the absence of the host recA gene product

Genetic Map of Bacteriophage [var phi]X174

Bacteriophage [var phi]X174 temperature-sensitive and nonsense mutations in eight cistrons were mapped by using two-, three-, and four-factor genetic crosses. The genetic map is circular with a total length of 24 × 10−4wt recombinants per progeny phage. The cistron order is D-E-F-G-H-A-B-C. High negative interference is seen, consistent with a small closed circular deoxyribonucleic acid molecule as a genome

Isolation of a Chloramphenicol-Resistant Protein From λ-Infected Cells

During infection with bacteriophage ϕX174, a protein, made in the presence of 30 γ chloramphenicol/ml but not made in the presence of concentrations greater than 100 γ/ml, has been shown to be essential for viral DNA replication. A protein with similar chromatographic properties and “chloramphenicol resistance” has now been demonstrated in cells infected with λ bacteriophage