- Volume 29, Issue 3, 1962

SUMMARY: The catabolic pathways for the utilization of glucose and gluconate in one representation of each of five species of Arthrobacter were studied by the respirometric method (Wang et al. 1958). The results indicate that these Arthrobacter organisms can be classified into two groups on the basis of their catabolic behaviour. The first group (Arthrobacter ureafaciens, A. globiformis) relies primarily on the operation of the Embden-Meyerhof-Parnas pathway and, to some extent, the hexose monophosphate pathway for the assimilation of glucose. In the second group (A. simplex, A. pascens, A. atrocyaneus) glucose is catabolized primarily by way of the intermediary formation of gluconate; the Entner-Doudoroff and the hexose monophosphate pathways appear to be the major routes for the assimilation of glucose and gluconate.

SUMMARY: During the submerged batch cultivation of a riboflavin-producing strain of Eremothecium ashbyi three phases were observed. The first phase was characterized by rapid growth of mycelium, rapid utilization and oxidation of glucose and a decrease of pH value caused by accumulation of pyruvic acid. Subsequently acetoin accumulated in the medium. Glucose was oxidized incompletely since only 1.8 μmole oxygen were consumed/ μmole glucose utilized. The end of this phase was marked by exhaustion of glucose and cessation of growth. The second phase began with sporulation and was characterized by rapid synthesis of cell-bound riboflavin. Simultaneously a rapid increase in catalase activity and decreases of pyruvate and acetoin were observed. This was accompanied by a marked decrease in Qo2 on glucose while the Qo2 on pyruvate, threonine or acetaldehyde increased to a maximum. Ammonia accumulated in the medium and alkaline pH values were reached. The third phase was characterized by autolysis of mycelium which led to the release of riboflavin and to a decrease of enzymic activities. A comparison of all important physiological parameters was made with two strains of E. ashbyi of different riboflavin productivity. On the basis of correlation between riboflavin formation, catalase activity and respiration on acetaldehyde, an hypothesis is proposed to explain over-production of riboflavin by a shift from the initial eytochrome type of terminal respiration to the flavoprotein type which is, however, accompanied by over-production of the flavin prosthetic group.

SUMMARY: The timing of cell and nuclear division of certain enteric bacteria was determined under conditions of balanced growth. Organisms were grown in a high refractive index medium and photographed at frequent intervals with a phase-contrast microscope. This allowed an estimation of the time between successive divisions of nuclei and cells (interdivision times) and the growth rate of each individual. The interdivision times of cell and nuclear divisions had a similar degree of variation (coefficients of variation of about 20%). The interdivision times of sister cells and sister nuclei were positively correlated to a significant degree. The correlation between mothers and daughters was negative to a significant degree in some, but not all, experiments. The correlation between interdivision times of a cell and that of its corresponding nucleus was positive in most experiments.

The rate of mass increase of individual cells was estimated by measuring the rate of elongation. Within the limitations of the method of observation, it could be concluded that cells grew exponentially between successive divisions. Different individuals grew with very nearly the same rate constant. The variation in size of cells at the time of nuclear and cell division was smaller (coefficients of variation of about 10%) than that of the interdivision times.

Some observations on the morphological changes of nuclei during growth and division are presented.

SUMMARY: A model for the statistics of cell division is proposed. The model assumes: (1) that growth at the cellular level is deterministic; (2) that the mean size of a cell at division is under cellular and environmental control; (3) that the distribution of sizes of cells at division has a small coefficient of variation, and is independent of the size at previous divisions; (4) that the cell divides nearly into equal halves. The observed coefficient of variation of the life-length distributionf f (t) results from a twofold smaller coefficient of variation in the distribution of cellular mass at division, g (c). The magnification of the coefficient of variation results from the fact that the mass variable enters twice, once in determining the size of cell formed at division, and, secondly, in determining the size of the cell when it in turn divides. In the expression for T, these sizes enter as the logarithm of their ratio. These mathematical operations contribute to the increased coefficient of variation of the f (T) distribution over the g (c) distribution. The skewed nature of the f (T) distribution is attributable to a number of causes. We feel that an important source of the skewness is due to deviations from equi-partition of cell constituents at division. In this respect the present model is in disagreement with previous models which presume that the skewness results from the statistics of a small number of molecular events taking place inside each cell. The experimentally observed positive sister-sister life-length correlation and the negative mother-daughter life-length correlation are explained by the model. Deviations from the predicted values of + 0.5 and —0.5, respectively may be explained in part by deviation from equal distribution of cell contents at division. Deviations of the correlations in excess of these, observed in some cases, imply the existence of the other biological processes. The size distribution of cells in balanced growth cultures based on this model is given.

SUMMARY: Sixty-three wild strains of Proteus mirabilis were investigated. All 55 strains comprising groups 1 a and 1 b were found to be cryptic with regard to sucrose fermentation; they possessed competent enzyme systems but did not normally ferment the sugar. No enzyme capable of cleaving this sugar was extracted from the 3 strains of group 2 and the 5 strains belonging to group 3. Partially purified enzyme preparations from two strains of P. vulgar is and two cryptic P. mirabilis strains were investigated; all four were constitutive β-D-fructofuranosidases capable of splitting raffinose to melibiose and fructose. Sucrose uptake studies showed that strains of groups 1a, 1b and 2 did not accumulate sucrose from 1% (w/v) solution; the strains of group 3 accumulated large amounts of sucrose. None of the P. mirabilis strains was permeable to maltose. The permeability barrier for sucrose was overcome by increasing its concentration to 5% (w/v). Under these conditions groups l a and 1b strains fermented sucrose in peptone water within 36 hr. Sodium deoxycholate also changed the permeability barrier of some of the cryptic strains, enabling them to ferment 1% (w/v) sucrose promptly. After 3–11 days in 1% (w/v) sucrose peptone water all 55 cryptic P. mirabilis, as well as the strains of group 3 fermented sucrose.

This fermentation was not caused by wild-type organisms, but resulted from the selection of sucrose-positive mutants which arose from the former and were capable of prompt sucrose fermentation. The mutants of strains of group 3 arose at lower rates than those from the cryptic strains. It is concluded that selective permeability to sucrose and β-D-fructofuranosidase activity are genetically distinct properties of Proteus. A scheme for the classification of phenotypes of P. hauseri is presented.

SUMMARY: The state of colicinogenic factors E2, I and V (col E2, col 1 and col V) In Escherichia coli K 12 studied. The analysis of the results of conjugation experiments involving different Hfr or F+ and F− strains shows that: (1) The frequency transfer of these colicinogenic factors differs markedly: col V is tr with maximum efficiency, col E2 and col I, on the contrarv, only at low frequency. (2) Each colicinogenic factor is transferred from different type of Hfr or F+ strains with similar frequencies. (3) They linked with chromosomal markers. (4) The non-colicinogenic character of the donor parent is never transmitted to recombinants. (5) Zygotes that have received col V, transmit it to all daughter cells. All these ults lead to the conclusion that colicinogenic factors E2 I and V are in an extrachromosomal state in F+ and Hfr bacteria. The same; would apply to their state in F− bacteria, since the results with inogenic factor V seem to indicate that this factor replicates in of bacteria autonomously and at a faster rate than the chromosome.

SUMMARY: The air in a valley near a stream and in an exposed site on a small hill at Silwood Park, near Ascot, Berkshire, was sampled from 14 May to 25 September 1958 at half a metre above the ground by a Hirst automatic volumetric spore trap. Seasonal periodicities of 26 categories of fungus spores and 7 categories of pollen grains are given as 6-day running means of the daily average number of spores per cubic metre of air. Estimated hourly concentrations of spores for 6 consecutive days are given for three fungus spore types and two pollens. The diurnal periodicity is given for these groups. There were 2–6 times more spores at site S near the stream than at the exposed site M. There were 4.9 times more spores of ascomycetes at S than at M. 3 times as many spores of basidiomycetes but only 1.4 times as many from fungi imperfecti. The proportion of the different types of spores at the two sites varied; 14% of spores at S were from ascomycetes, 7% at M; 17.5% of those at S were from fungi imperfecti and 32% of those at M. Tree pollen grains were equal in number at both sites but there was 2.8 times more grass pollen and 6.5 times more weed pollen at S than at M. Urtica pollen was 8.1 times as common at S and made up 55% of the total pollen in that area, but only 24% of the total at M, mainly because of the local abundance of nettle plants. The results suggest that the ecology of an area has a major influence on its air-spora through local flora and microclimate.

SUMMARY: The effectiveness of a number of different materials in the negative staning method for electron microscopy of viruses is evaluated. Shadowing was used to study the degree of distortion suffered by the specimen. Changes in pH value which occurred while the negative staining solution was trying were measured in those materials which gave the most satisfactory results in the electron microscope. The ultimate resolution of the method is discussed and demonstrated. It was important to de-grease supporting film: perforated carbon films were found valuable for obtaining good contrast.

SUMMARY: Factor III of anthrax toxin, which increases the lethality of mixtures of factors I and II for mice and decreases their capacity to produce oedema in the skin of rabbits, has been purified. The final preparation showed a single peak in the ultracentrifuge and a single band on paper electro-phoresis. but it might still contain more than one serological component. The final preparation was a protein (N = 15.1%) containing all the usual amino acids but no carbohydrate, phosphorus, lipid or ash.

SUMMARY: Rabbit pox virus grown in tissue culture cells and vaccinia virus grown on rabbit skin have been purified as follows. The virus was sedimented and washed once by centrifugation to provide a tenfold virus concentrate. This semi-purified material was layered on top of a sucrose density gradient and centrifuged to produce a zone of virus separated from zones of urgenty. Sucrose was removed from the purified virus suspension by through washing in the centrifuge. About 40% of the original infectivity was recovered in the purified material which consisted almost entirely of virus particles when examined in the electron microscope. Control experiments indicated a maximum of 5% protein impurity. Almost complete seperation of vaccinia haemagglutinin and virus was obtained.

SUMMARY: Suspensions of Staphylococcus aureus grown aerobically on nutrient broth oxidized glucose, acetate and intermediates of the tricarboxylic acid cycle, but glucose-grown organisms oxidized glucose only. The inability of glucose-grown staphylococci to oxidize intermediates of the tricarboxylic acid cycle was correlated with diminished succinate and isocitrate dehydrogenase activity in cell-free extracts as compared with extracts from organisms grown without glucose. Suspensions of aerobically-grown staphylococci fermented glucose anaerobically at only about one third the rate observed with anaerobically-grown organisms. The nicotinamide-adenine dinucleotide-linked lactate dehydrogenase activity in extracts of the anaerobically-grown organisms was about ten times higher than that in extracts of aerobically-grown staphylococci.

SUMMARY: A method is described for the preparation of highly competent (transformable) bacteria of Haemophilus influenzae. After three successive treatments, i.e. aerobic growth, anaerobic incubation and incubation in saline containing a few per cent broth, transformation frequencies close to 5% have been obtained.

Competent bacteria absorb DNA very fast. Untransformable ones lack this ability. Absorption is inhibited by dinitrophenol or arsenate; it is not inhibited by chloramphenicol. This suggests the participation of an enzyme system.

Development of competency is blocked by dinitrophenol, arsenate or chloramphenicol. It is strongly dependent upon temperature. It is not influenced by the absorption of one or two DNA molecules per bacterium.

SUMMARY: The conspicuous, large, high refractive index, sudanophilic granules of Rhizobium trifolii appeared to be aggregations of polymeric β-hydroxybutyric acid, probably closely associated with the cytoplasm. They became more conspicuous as the organism aged, provided that carbohydrate was in excess. A well-grown culture contained 40–50% polymer, based on cell dry weight. Relatively large cytoplasmic granules (50–80 mμ) were a feature of this organism whether in fixed and sectioned cells or in material shadowed after mechanical disintegration.

Classical ‘double’ (? lipoprotein) membranes were demonstrated both for the cell wall and the cytoplasmic membrane. Carefully fixed and embedded material often showed an accumulation of material between the two double membranes, especially at one or both ends, without any evidence of gross damage in the sectioned organisms.

SUMMARY: The cell walls from Rhizobium trifolii, grown under both ‘normal’ and ‘calcium-deprived’ conditions, were analysed in an attempt to detect a chemical cause for the apparent weakness or looseness of the walls in calcium-deprived organisms. The organic components typical of Gram-negative cell walls were present in normal and calcium-deprived cells. The latter concentrated most of the small amount of available calcium in the walls, which, however, contained only 60% of that present in the walls of normal organisms. Magnesium was not able to substitute for calcium as a wall component.