The growth of bacteriophage

1. An anti-Escherichia coli phage has been isolated and its behavior studied. 2. A plaque counting method for this phage is described, and shown to give a number of plaques which is proportional to the phage concentration. The number of plaques is shown to be independent of agar concentration, temperature of plate incubation, and concentration of the suspension of plating bacteria. 3. The efficiency of plating, i.e. the probability of plaque formation by a phage particle, depends somewhat on the culture of bacteria used for plating, and averages around 0.4. 4. Methods are described to avoid the inactivation of phage by substances in the fresh lysates. 5. The growth of phage can be divided into three periods: adsorption of the phage on the bacterium, growth upon or within the bacterium (latent period), and the release of the phage (burst). 6. The rate of adsorption of phage was found to be proportional to the concentration of phage and to the concentration of bacteria. The rate constant ka is 1.2 x 10–9 cm.8/min. at 15°C. and 1.9 x 10–9 cm.8/min. at 25°. 7. The average latent period varies with the temperature in the same way as the division period of the bacteria. 8. The latent period before a burst of individual infected bacteria varies under constant conditions between a minimal value and about twice this value. 9. The average latent period and the average burst size are neither increased nor decreased by a fourfold infection of the bacteria with phage. 10. The average burst size is independent of the temperature, and is about 60 phage particles per bacterium. 11. The individual bursts vary in size from a few particles to about 200. The same variability is found when the early bursts are measured separately, and when all the bursts are measured at a late time

The rate of bacteriophage inactivation by filtrates of Eschericia coli cultures

The inactivation of bacteriophage by substances from susceptible bacteria has been studied by Burnet (1) and Freeman (2). Its inactivation by antisera has been studied by Andrewes and Elford (3) and Burnet, Keogh, and Lush (4). Recently Ashenburg et al. (5) reported that saline solutions of gum arabic, starch, or glycogen inactivated an anti-Klebsiella pneumoniae phage. We have studied in more detail the rate of phage inactivation by culture filtrates of the susceptible bacteria in order to determine the dependence of the process on phage and inhibitor concentrations

Sulfhydryl oxidation-reduction potentials derived from thermal data

The isolation of glutathione by Hopkins in 1921 and his experiments suggesting that this compound is probably an intermediary in biological oxidations and reductions awakened an active interest in the biological significance of sulfhydryl compounds in general (1, 2). Among the fundamental data pertaining to these compounds are their oxidation-reduction potentials. Soon after the discovery of glutathione a number of attempts were made to measure these potentials by electrometric and calorimetric methods. In all except the most recent investigations the potential observed in aqueous solutions with noble metal electrodes was independent of the concentration of the oxidized form (R—S—S—R) (3-5)

How Anisotropic is our Universe?

Large-scale cosmic microwave background anisotropies in homogeneous, globally anisotropic cosmologies are investigated. We perform a statistical analysis in which the four-year data from the Cosmic Background Explorer satellite is searched for the specific anisotropy patterns predicted by these models and thereby set definitive upper limits on the amount of shear, $(\sigma/H)_0$ and vorticity, $(\omega/H)_0$, which are orders of magnitude stronger than previous constraints. We comment on how these results might impact our understanding of primordial global anisotropy.Comment: 12 pages (1 figure), uses RevTex and psfig, submitted to PR

Teachers\u27 Views of the Treatability of Children\u27s School Adjustment Problems\u27

One-hundred thirty-four primary grade teachers rated each of nine hypothetical referrals, depicting three predominant types of school adjustment problems (acting-out, shy-anxious, learning), on four dimensions: (a) appropriateness of referring the child to the school\u27s mental health services, (b) ease or difficulty for a mental health person to work with such a child, (c) how much a mental health person would enjoy working with the child, and (d) a treatment-prognosis estimate. Shy-anxious children generally received the most positive ratings. Teacher judgments were compared to prior, similar judgments made by mental health personnel. The latter gave significantly higher appropriateness ratings, indicated that the children would be significantly less difficult and more enjoyable to work with, and judged prognosis to be more favorable. An important deviation from this pattern of findings is considered

Nonprofessional and Professional Help-Agents\u27 Views of Interventions with Young Maladapting Children

The expectations of nonprofessional and professional help-agents about helping interventions with young children experiencing different types of school adjustment problems (i.e., aggressive-acting out, shy-anxious, and learning problems) were studied. The two groups responded similarly. Shy-anxious children were seen as most appropriate for the intervention, the easiest and most enjoyable group to work with, and as having the best prognoses. These four sets of judgments were relatively independent of each other. A connection was made between the current data and prior findings suggesting that shy-anxious children have more favorable treatment outcomes than other groups