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

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

Advance crew procedures development techniques: Procedures generation program requirements document

The Procedures Generation Program (PGP) is described as an automated crew procedures generation and performance monitoring system. Computer software requirements to be implemented in PGP for the Advanced Crew Procedures Development Techniques are outlined

Direction of Translation and Size of Bacteriophage [var phi]X174 Cistrons

Translation of the bacteriophage [var phi]X174 genome follows cistron order D-E-F-G-H-A-B-C. To establish this, the position of a nonsense mutation on the genetic map was compared with the physical size (molecular weight) of the appropriate protein fragment generated in nonpermissive cells. Distances on the [var phi]X174 genetic map and distances on a physical map constructed from the molecular weights of [var phi]X174 proteins and protein fragments are proportional over most of the genome with the exception of the high recombination region within cistron A

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

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

Inhibitor of chromosomal DNA replication in xenopus: the turhuter protein

A composition is provided that inhibits DNA replication in activated cell-free extracts of Xenopus eggs, which is prepared by a process comprising subjecting homogenates of Xenopus ovaries to a series of chromatographic separations so as to isolate a purified fraction comprising a protein having a molecular weight ofabout 245 kDa

The ephemeral resource patch concept

Ephemeral resource patches (ERPs) – short lived resources including dung, carrion, temporary pools, rotting vegetation, decaying wood, and fungi – are found throughout every ecosystem. Their short-lived dynamics greatly enhance ecosystem heterogeneity and have shaped the evolutionary trajectories of a wide range of organisms – from bacteria to insects and amphibians. Despite this, there has been no attempt to distinguish ERPs clearly from other resource types, to identify their shared spatiotemporal characteristics, or to articulate their broad ecological and evolutionary influences on biotic communities. Here, we define ERPs as any distinct consumable resources which (i) are homogeneous (genetically, chemically, or structurally) relative to the surrounding matrix, (ii) host a discrete multitrophic community consisting of species that cannot replicate solely in any of the surrounding matrix, and (iii) cannot maintain a balance between depletion and renewal, which in turn, prevents multiple generations of consumers/users or reaching a community equilibrium. We outline the wide range of ERPs that fit these criteria, propose 12 spatiotemporal characteristics along which ERPs can vary, and synthesise a large body of literature that relates ERP dynamics to ecological and evolutionary theory. We draw this knowledge together and present a new unifying conceptual framework that incorporates how ERPs have shaped the adaptive trajectories of organisms, the structure of ecosystems, and how they can be integrated into biodiversity management and conservation. Future research should focus on how inter- and intra-resource variation occurs in nature – with a particular focus on resource × environment × genotype interactions. This will likely reveal novel adaptive strategies, aid the development of new eco-evolutionary theory, and greatly improve our understanding of the form and function of organisms and ecosystems. © 2022 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society

Discovery of Very High Energy gamma - ray emission from the extreme BL Lac object H2356-309 with H.E.S.S

The understanding of acceleration mechanisms in active galactic nuclei (AGN) jets and the measurement of the extragalactic-background-light (EBL) density are closely linked and require the detection of a large sample of very-high-energy (VHE) emitting extragalactic objects at varying redshifts. We report here on the discovery with the H.E.S.S. (High Energy Stereoscopic System) atmospheric-Cherenkov telescopes of the VHE Gamma-ray emission from H2356 - 309, an extreme BL Lac object located at a redshift of 0.165. The observations of this object, which was previously proposed as a southern-hemisphere VHE candidate source, were performed between June and December 2004. The total exposure is 38.9 hours live time, after data quality selection, which yields the detection of a signal at the level of 9.0$\sigma$ (standard deviations) .Comment: To appear on proceeding of 29th International Cosmic Ray Conference (ICRC 2005