- Volume 34, Issue 3, 1964

Summary: The distributions of penicillinase in populations of uninduced, induced and constitutive cultures of Bacillus licheniformis strains 749 and 749/c each showed a large positive skew. Analysis of the enzyme distribution in the uninduced population as a Poisson distribution showed that penicillinase molecules were produced not as independent random events, but in clusters containing 1100 molecules. There were 0.4 (average 0.85) clusters/organism. The fundamental random event resulting in the formation of a cluster of penicillinase molecules may be the formation of one enzyme-forming site capable of producing 1100 such molecules. Analysis of the enzyme distribution in the constitutive population showed that in this case penicillinase was produced in groups of 55,000 molecules, or fifty of the clusters of penicillinase found in the organisms of the uninduced population. This may be the number of enzyme-forming sites made by a constitutive penicillinase gene during the period between its formation and replication. Analysis of the enzyme distribution in the induced population showed that the organisms did not respond equally after induction, but all organisms probably increased their rates of penicillinase synthesis. Enzyme partition can be highly asymmetric when an organism divides; the enzyme molecules do not appear to be able to diffuse freely within the cell cytoplasm, but may be associated with some structurally rigid material in the organisms.

Summary: Anaerobic cultures of Pseudomonas aeruginosa died rapidly in the absence of nitrate and death was normally followed by extensive autolysis. A mutant which did not undergo extensive autolysis was isolated. Anaerobic cultures of Salmonella bethesda did not die or lyse even after prolonged incubation. The protein and lipid content of the parent P. aeruginosa cell walls altered during ageing in contrast to S. bethesda walls which did not alter greatly as the organisms aged. The amino acid and amino sugar content of the three strains was determined. The diaminopimelic acid, glycine, alanine, glutamic acid, glucosamine, muramic acid and glucose content of the parent cell walls decreased by 50% as the organisms aged. The mutant strain of P. aeruginosa and S. bethesda walls showed no such change in ageing. Chemical changes similar to ageing could be produced in the cell walls of P. aeruginosa by incubation with an autolysin obtained from old cultures of the parent strain.

Summary: Glucose and galactose are accumulated against a concentration difference by Streptococcus faecalis strain 10c1 which has been treated with iodoacetate to eliminate glycolysis. The rate and extent of accumulation are greater for glucose than for galactose but both processes show saturation kinetics, stereospecificity, and sensitivity to metabolic inhibitors. Accumulated sugar does not exchange with glucose or galactose in the external medium. Loss of internal sugar is a relatively slow first-order reaction. Both accumulation and loss are temperature dependent. Preincubation of the organisms in arginine increases the rate and extent of accumulation and decreases the rate of loss. A model is proposed in which hexose accumulation results from an energy-dependent adsorption to specific, thermolabile receptors.

Summary: Gibberella fujikuroi was allowed to grow on unlabelled medium until gibberellic acid (GA) was being produced, and samples of mycelium were then transferred to a substrate containing 14C-acetate. Pure 14C-GA was isolated from the medium. The specific activity of the 14C-GA was increased by transferring mycelium to a second labelled substrate 6 hr after the first transfer. The specific activity was not increased when unlabelled glucose was present in the transfer medium, or when anaerobic conditions were maintained after transfer. Most of the 14C-GA was produced during the 48 hr following transfer. A large proportion of the 14C was lost as 14CO2, and most of this was produced during the 40 hr after transfer. After this period little GA was produced, but the evolution of unlabelled CO2 continued.

Summary: Delay in deoxyribonucleic acid (DNA) synthesis after use of ultraviolet radiation to induce Escherichia coli lysogenic for phage λ was due to the irradiation procedure; the same delay was found in non-lysogenic bacteria exposed to the same dose of radiation. After infection with phage λ c or λ V in 0.02 m-MgSO4, DNA synthesis began without delay when complete medium was added. During vegetative development of phage in induced bacteria, 81--89% of the DNA synthesized was accounted for in the phage progeny, indicating that host DNA synthesis is much diminished and may be completely inhibited. Mature phage particles arose soon after the appearance of serum blocking power (SBP) and endolysin activity. Induced bacteria synthesized up to 15 times more SBP than was incorporated into complete phage particles: the excess SBP was not sedimented at 40,000 g (unlike phage particles), but about half was sedimented at 90,000 g, the rest remaining in the supernatant fluid. Whilst protein and RNA synthesis in infected or induced bacteria was initially similar to that in the control, there was a marked decrease of synthesis in the second half of the latent period.

Summary: A polarographic technique and Starkey's alkali method have been applied to the qualitative analysis of thiosulphate, trithionate and pentathionate and to the quantitative analysis of tetrathionate in filtrates of bacterial cultures grown in an inorganic medium containing sodium thiosulphate. Five strains of autotrophic thiobacilli and one strain of a heterotrophic bacterium produced polythionates. During thiosulphate oxidation by two autotrophic strains which resembled Thiobacillus thioparus, tetrathionate, small amounts of trithionate, pentathionate and abundant elemental sulphur were produced and the pH fell from c. 7.0 to c. 3.0. In cultures of one of the three autotrophic strains which resembled T. thiocyanoxidans, about half as much tetrathionate, with even smaller amounts of trithionate and pentathionate, was found; abundant sulphur was precipitated and the pH fell to c. 4.0. In cultures of the two other strains resembling T. thiocyanoxidans, small amounts of tetrathionate were detected only occasionally; trithionate and pentathionate were not found, sulphur was deposited and the pH fell to c. 4.5. Much tetrathionate, as well as trithionate and pentathionate, were all readily identified in cultures of the heterotrophic organism; the pH rose to c. 8.7 and no sulphur was formed.

Summary: A membrane surrounding poly-β-hydroxybutyrate (PHB) granules isolated from both Bacillus cereus and B. megaterium has been demonstrated by the carbon-replica technique and electron microscopy. Some general features and properties of both the membrane and PHB granules are discussed.

Summary: A method is described for the isolation in pure culture of the predominant cellulolytic bacteria which occur in the ovine rumen. Ten isolates of cocci were obtained from the rumen contents of one sheep conditioned to lucerne hay, and were identified as Ruminococcus albus. All ten isolates degraded xylan in addition to cellulose and cellobiose and a comparative study of the end-products of fermentation of xylan and cellobiose was made. The rates of growth on cellulose and cellobiose were compared, and the role of these cocci in the breakdown of the fibrous part of the diet assessed.

Summary: Substrate-accelerated death (Postgate & Hunter, 1963a) was observed with glycerol-, glucose-, ribose-, ammonium- or phosphate-limited populations of Aerobacter aerogenes grown in defined media and starved in non-nutrient buffer; sulphate- or magnesium-limited organisms did not show this. Glucose or pyruvate accelerated death of starved populations obtained from a complex medium. Lactate-accelerated death of Escherichia coli and glucose-accelerated death of Serratia marcescens were also observed with populations of appropriate nutritional status. Glycerol-accelerated death of glycerol-limited A. aerogenes occurred with organisms from batch or continuous cultures grown at various pH values; it showed a population effect and was particularly pronounced in 0.15 m-NaCl buffered with phosphate. Continued presence of glycerol was necessary and the glycerol was metabolized. Survivors showed prolonged division lags. Tricarboxylic acid cycle intermediates, but not glucose or ribose, also accelerated death. Glycerol-accelerated death was not delayed by malonate, fluoride or fluoracetate; iodo-acetate delayed its onset but did not affect its rate; uncoupling agents antagonized it though they were themselves toxic. Glycerol-accelerated death was not accompanied by accelerated break-down of the osmotic barrier, nor by leakage of materials associated with cold shock nor by acquiring sensitivity to cold shock. No catabolism of DNA or protein accompanied it; polysaccharide was synthesized; no change in the rate of degradation of RNA was observed. Coloured substances, pyridine nucleotides, white-fluorescent material and material which absorbed at 220-230 mμ were released during glycerol-accelerated death. Magnesium ions prevented glycerol-accelerated death.

Summary: Interferon was produced in chick embryo cell cultures or in chick embryos by five viruses and in mouse embryo cell cultures or mouse lungs by two viruses. The slopes of the log dose response lines for the five chick inter-ferons were compared by using vaccinia virus as the assay virus. Analysis of variance showed that they did not differ significantly. Partially purified interferon gave the same slope as the crude preparations. These findings allowed a comparison to be made of relative yields of interferon induced by different viruses in the same cell system. Viruses differed widely in their ability to induce interferon. Chikungunya virus induced about 70 times more interferon than did vaccinia or Newcastle disease virus and 2.6 times more interferon than Kumba virus. The slopes of the log dose response lines for two interferon preparations were compared by using Chikungunya virus as the assay virus. Analysis of variance showed that they were not significantly different. A comparison of the vaccinia and Chikungunya assays for interferon showed that the Chikungunya assay was approximately 2.9 times more sensitive when the amount of interferon depressing the plaque count by 50% (PDD 50 doses) were compared. An analysis of variance showed that the difference in slope between the two assays was small but approaching significance. Mouse interferon, induced by two viruses, yielded parallel dose response lines. However, the slope of the curves for mouse interferon was significantly different from that for chick interferon. Because of this difference in slope, interferon production by the same virus in the two cell types could not be validly compared.

Summary: The characteristics of l-histidine uptake by Dictyostelium discoideum, after removal of the food supply, are described. There were only small differences in the rate of histidine uptake and incorporation into protein with changing pH value. It is concluded that the site of histidine stimulation of the rate of development must be at the cell surface or outside the cell. The production of urocanic acid from histidine is described. At the concentrations produced, urocanate had little or no effect on the rate of morphogenesis. However, at higher concentrations, urocanate and a variety of imidazole-containing compounds were stimulatory.

Summary: Vaccinia virus subjected to various repeated treatments and then negatively stained with potassium phosphotungstate was examined with the electron microscope. To obtain reproducible results it was necessary to standardize the preparation procedure. The standarized method now recommended is that the virus should be mixed with stain before being placed on the electron microscope grids and the grids then immediately examined or dried for 1 hr in a vacuum of at least 1 x 10−3torr. The staining procedure may be altered to vary the degree of penetration of stain so as to reveal either internal or external detail.