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Volume 23,
Issue 1,
1960
Volume 23, Issue 1, 1960
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Pigments of Trichophyta
More LessSummary: Pigments possessing the properties of anthraquinones were isolated from three species of the genus Trichophyton. These pigments were characterized by their absorption spectra, their colour changes with various reagents, and their Rf values on paper chromatography. Most of these pigments were common to more than one species.
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The Preparation and Properties of Spheroplasts of Aerobacter aerogenes
More LessSummary: Cells of Aerobacter aerogenes growing in a nutrient medium were lysed by 1000 u. penicillin/ml. When the medium contained penicillin and sucrose, bacterial mass continued to increase on incubation, although no further cell division took place. After growth for 3 hr. in the presence of penicillin, all the rod-shaped bacteria were converted to fragile spheroplasts. The internal osmotic pressure of the spheroplasts was estimated by direct counts of the intact cells in solutions containing various concentrations of sucrose, sodium chloride or mixed phosphates. Measurements of optical densities of suspensions were unsuitable for the estimation of the numbers of spheroplasts. Morphological study suggested the existence of a spheroplast cell wall outside the protoplasmic membrane.
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Lysis of Protoplasts of Micrococcus lysodeikticus by Ionic Detergents
More LessSummary: The time course of lysis of protoplasts of Micrococcus lysodeikticus was studied by spectrophotometric methods. The lytic agents used were sodium dodecylsulphate and a range of cationic detergents which each possessed a n-C12 alkyl chain and comprised the amine hydrochloride, the trimethylammonium bromide, the pyri-dinium bromide and the quinolinium bromide. Also the inhibition of lysis by uranyl ions and the action of detergents on isolated protoplast membranes were investigated. It is concluded that the cationic detergents act on the complex phosphatidic acid lipid component of the protoplast membrane and that lysis results from secondary osmotic effects. Access to the reactive site by agents of similar hydrophilic-hydrophobic balance is controlled by steric factors. Anionic detergents, however, cause direct disintegration of the protoplast, membrane independent of osmotic stresses, probably by interaction with the membrane protein moiety; a concurrent interaction with lipid, possibly through a lipoprotein complex, is not definitely excluded.
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Lysis of Protoplasts of Micrococcus lysodeikticus by Alcohols
More LessSummary: The time course of lysis of protoplasts of Micrococcus lysodeikticus by n-ethanol. n-propanol, n-butanol and isoamyl alcohol was studied spectrophotometrically. The relative activity for lysis increased with the molecular weight of the alcohol used. Equal degrees of lysis resulted at equal thermodynamic activities of the alcohols. The high lytic concentrations of ethanol and propanol produced side effects which obscured the lysis/time curves. n-Butanol showed time delays before the onset of lysis; the significance of this is discussed in terms of protoplast-membrane structure. Because of similarities with lysis by cationic detergents and with the extraction of scrum lipids in the presence of alcohols, it is concluded that the alcohols tested acted on the lipid component of the protoplast membrane and that lysis resulted from the disruption of membrane permeability.
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The Additive Effect of Glycine and other Amino Acids on the Induction of the L-Phase of Group A β-Haemolytic Streptococci by Penicillin and D-Cycloserine
More LessSUMMARY: The ability of glycine to induce L-phase of bacteria did not apply to group A β-haemolytic streptococci. In the presence of penicillin, glycine in a bacterial inhibitory concentration had a notably additive L-phase inducing property for streptococci. Reasons are given to support the view that this activity of glycine is limited to the induction of L-phase growth. A sharp increase in the yield of L-phase colonies was also observed when serine, threonine, methionine or alanine were tested under similar conditions. When the effectiveness of the racemate and both the isomers of these amino acids was compared, the d-isomer was the active substance in most cases. In one strain, the L-inducing and bacterial inhibitory action of the racemate and both isomers of methionine was tested simultaneously. The yield of L-phase colonies was found to be inversely proportional to the effect of the different stereoisomers on bacterial growth.
d-Cycloserine had a weak L-inducing effect on group A streptococci, but the combined action of d-cycloserine and glycine or dl-serine was equal to that obtained with penicillin and the same amino acids. Propagation of these L-phase organisms was possible in the presence of 1% (w/v) glycine and within a narrow range of concentrations of d-cycloserine. The additive effect of the amino acids cited towards penicillin and d-cycloserine for the induction of L-phase structures can be explained by the antibiotic property of high concentrations of glycine and some of the d-amino acids.
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Recombination of Characters Between Mutant Stocks of Vibrio cholerae, Strain 162
More LessSUMMARY: Crosses between two mutant strains derived from Vibrio cholerae, one requiring valine and isoleucine and the other arginine and purine, yielded recombinants when seeded together on a minimal medium containing l-asparagine. Other markers such as resistance or sensitivity to streptomycin and a lytic choleraphage, which were unselected under the experimental conditions, also segregated in the recombinants.
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Denitrification as Influenced by Photosynthetic Oxygen Production
More LessSummary: An attempt was made to detect interaction between photosynthesizing algae and denitrifying bacteria by cultivating Chlorella sp. with Pseudomonas stutzeri. Denitrification was inhibited by illumination of the mixed culture after a dark period of 3 hr. It is suggested that immediate inhibition is due to the molecular oxygen produced by the suspended algae and distributed homogeneously in the culture. A delay of this inhibition may be caused by uptake of oxygen by the denitrifiers at a more rapid rate than its production by the algae. Thus, the quantitative aspects of this interaction depend upon the particular conditions of cultivation used. The ecological implications are discussed.
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The Utilization by Yeasts of Acids of the Tricarboxylic Acid Cycle
More LessSUMMARY: Growth and respiration on intermediates of the tricarboxylic acid cycle as sole sources of carbon were studied with a number of different yeasts. The incorporation of [1:2-14C]acetate by acetate-respiring cells was studied with yeasts capable of utilizing exogenously supplied cycle intermediates (K +) and also with those unable to do so (K −). Enzyme systems were examined by using cell-free extracts. It was concluded that the difference between K + and K− yeasts was not one of a major metabolic pathway, but probably of the permeability of the intact cells. Evidence was found for the operation of the tricarboxylic acid cycle in yeasts under differing growth conditions, and for the operation of the glyoxylate cycle in yeasts growing on acetate.
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Some Observations on the Cytochemistry of Streptomyces
More LessSUMMARY: Tests for the distribution of sulphydryl groups, alkaline phosphatase, catalase, peroxidase in six species of Streptomyces showed that these occurred in greatest concentration in the young aerial mycelium, and especially at its points of origin or differentiation from the vegetative mycelium. In some species, these points of differentiation took the form of synnemata (coremia) of a distinctive appearance.
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The Effect of Deficiency of Iron, Zinc and Manganese on the Growth and Morpholoǵy of Nocardia opaca
More LessSUMMARY:A study of the trace element requirements of a strain of Nocardia opaca was made. Iron, zinc and manganese were required for optimum growth of the organism on glucose, sucrose, glycerol, gluconate and phenylacetate. Deficiency of manganese caused marked morphological changes in the organism during growth on all the substrates.
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Carotenoid Distribution in Certain Naturally Occurrinǵ Alǵae and in some Artificially Induced Mutants of Chlorella pyrenoidosa
More LessSUMMARY: The carotenoids of pure cultures of two members of the Class Chrysophyceae were examined; the main pigments in Ochromonas danica and Prymnesium parvum are fucoxanthin and β-carotene. The main carotenoids of Cyanidium caldarium are β-carotene and zeaxanthin; these observations support the view that this alga represents a transitional form between the cryptomonads and the green algae. The distribution of polyenes and carotenoids in a number of ultra-violet induced mutants of Chlorella pyrenoidosa is described.
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The Synthesis of Serine by Leuconostoc mesenteroides P60
More LessSUMMARY: Though CO2 is essential for the growth of Leuconostoc mesenteroides strain P60 in the absence of serine, 14CO2 is not incorporated into serine by the growing organism. The synthesis of serine was further studied by using suspensions of a variant strain of L. mesenteroides P60 which formed serine more actively than the parent strain. Glycine, formate, glucose, p-aminobenzoic acid and pyridoxal were required for the synthesis of serine by these suspensions. There was an additional requirement for CO2 only when the organisms had been incubated previously in phosphate-buffered glucose. Leucovorin satisfied the requirement for both CO2 and p-aminobenzoic acid.
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The Synthesis of Citrovorum Factor by Leuconostoc mesenteroides P 60
More LessSUMMARY: When incubated with p-aminobenzoic acid, formate and glucose, suspensions of a variant strain of Leuconostoc mesenteroides strain P60 formed two factors possessing folic acid activity. One of these factors behaved like rhizopterin in supporting the growth of Streptococcus faecalis strain R but not of Lactobacillus casei. The other, like leucovorin, supported the growth of Leuconostoc citrovorum. The synthesis of ‘citrovorum factor’ was enhanced 5- to 20-fold by the presence of CO2 in the gas phase. Sulphathiazole inhibited the synthesis of both factors, the inhibition being overcome competitively by p-aminobenzoic acid. Leucovorin was destroyed by suspensions of L. mesenteroides P60 in phosphate-buffered glucose. The diminution of activity for L. citrovorum (decrease of citrovorum factor) was decreased when the incubation was carried out in a CO2-enriched atmosphere. Ascorbic acid, which behaved similarly to CO2 in partially preventing inactivation of leucovorin by suspensions of L. mesenteroides P60 variant strain, also increased the synthesis of citrovorum factor from formate and p-aminobenzoic acid and partially satisfied the requirement of the growing L. mesenteroides P60 for CO2.
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A Study of the Factors Controlling Lactose-Fermentation in the Coliform and Paracolon Groups
More LessDetailed study of a representative paracolon strain showed that the delayed fermentation of 1% lactose coincided with the development of lactose-fermenting mutants, and that the essential difference between the normal non-lactose-fermenting (lac−) organisms and the lactose-fermenting (lac+) mutants was one of decreased permeability for lactose. Both types of organism showed the same degree of β-galactosidase activity when grown on lactose-free media; the permeability of the lac− organisms was increased by raising the concentration of lactose in the medium. On the assumption that permeability is governed by a specific permease which is genetically distinct from β-galactosidase, a hypothetical scheme based on these two factors together with the presence or absence of hydrogenlyase suggested the existence of six phenotypes among the paracolon bacilli. In an examination of 51 naturally occurring paracolon strains four of these phenotypes were demonstrated. Since the lactose-fermenting paracolon organisms differ from coliform bacilli merely in being less permeable to 1% lactose, whereas the non-lactose-fermenting organisms differ from both the other groups in lacking β-galactosidase activity, it is suggested that the term paracolon should not be applied to this last group but should be restricted to the late-lactose-fermenters. Alternatively, these could be classed within the coliform group.
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Disaggregation of Bacterial Cell Walls by Anionic Detergents
More LessIsolated cell walls of six Gram-negative bacteria were disaggregated by sodium dodecyl sulphate at all pH values between pH 2 and 9. Disaggregation as measured by decrease in turbidity showed maxima at pH 3 and 8. Salmonella gallinarum walls were disaggregated by alcohol sulphate compounds with alkyl chain lengths of 10, 12, 14 and 16 carbon atoms; maximum activity was observed with the C14 homologue. No sulphydryl groups were detected on disaggregation of the walls of S. gallinarum and p-chloromercuribenzoate had no protective action. Autolytic enzymes of Vibrio metchnikovii do not contribute to the dissolution of the walls of this organism by sodium dodecyl sulphate.
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Excretion of Nicotinic Acid by Biotin-Deficient Saccharomyces cerevisiae
More LessSummary: Growth of a strain of Saccharomyces cerevisiae in a glucose salts vitamins medium, containing suboptimal concentrations of biotin, was accompanied by the appearance in the medium of a free form of nicotinic acid, and also a heat-labile combined form of this substance; these were identified chromatographically as nicotinic acid and desamido-DPN (nicotinic acid adenine dinucleotide), respectively. The effect of biotin concentration and incubation time on the excretion of these substances is reported. The presence of adenine in the growth medium caused a marked decrease in the excretion of both forms of nicotinic acid, but hypoxanthine and 4-amino-5-imidazole carboxamide had no observable effect. Addition of dl-aspartic acid to the medium also brought about a decrease in the amounts excreted, although concentrations of this amino acid in excess of 0·5 × 10−3 m stimulated excretion of desamido-DPN. It is concluded that excretion of free nicotinic and desamido-DPN is largely the result of an impairment in the ability of the biotin-deficient yeast to produce adenine, which in turn leads to a derangement in the synthesis of pyridine nucleotides.
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Mineral Requirements and other Characters of Selected Marine Bacteria
More LessSUMMARY: Marine bacteria from Atlantic coastal waters off Florida, isolated by a technique assuring that all would grow on a sea-water medium but not on a distilled water medium, were studied; 96 of 100 original isolates were characterized by morphological and some physiological properties, particularly those related to mineral responses. All isolates were Gram-negative rods or spiral forms, grew well in a simple saline-peptone medium, and most were pigmented and motile. All isolates required NaCl for good growth, and groupings could be clearly established for those whose mineral nutrition was satisfied, in a casein digest broth, by adding NaCl only, NaCl + KCl, NaCl + Mg salts, or all three salts. Lytic susceptibility in various mineral solutions and growth tolerance to various salt levels were studied. Some overall similarities, and a few correlations between mineral nutrition and physiological versatility, were established.
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Studies upon an Oral Aerobic Actinomycete
More LessSUMMARY: An aerobic actinomycete isolated regularly from the human mouth is described. This organism possesses the cultural, morphological and biochemical characters of Ørskov’s Group 2b, or more specifically, the genus Nocardia. Although the results of cell-wall analyses differ from those obtained in this and previous studies upon other species of Nocardia, we nevertheless feel that provisional classification in the genus Nocardia is valid upon the present evidence. The specific name N. salivae is proposed.
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The Bactericidal Action of Streptomycin on Staphylococcus aureus and Some Accompanying Biochemical Changes
More LessSome factors which affect the killing by streptomycin of Staphylococcus aureus in growing cultures have been investigated. In short-term experiments, streptomycin is not bactericidal under conditions in which growth of the organisms cannot occur (low temperature, absence of nitrogen source, presence of growth-inhibitory concentrations of chloramphenicol). The rate of killing of organisms growing anaerobically is considerably lower than that of organisms growing aerobically. Streptidine can partially reverse the growth inhibitory effect of streptomycin. During the period in which growth becomes inhibited by streptomycin, the rates of incorporation of 14C-labelled precursors into the major cell constituents, and of synthesis of nucleic acids, are reduced simultaneously, and no large changes occur in the total quantities of amino acids or 260 mμ-absorbing substances in the metabolic pool. During this period the rate of metabolism of glucose via the Embden-Meyerhof pathway is decreased, but there is no change in the proportion of the total glucose oxidized which is metabolized via a C1-preferential oxidation. The Q o2 value for oxidation of glucose by organisms harvested when inhibition of growth by streptomycin is first detectable is lower, by about 20%, than that of normal organisms, and falls to c. 30% of normal when growth is fully inhibited. At this time the Q o2 values for oxidation of glycerol, lactate and formate are also reduced, by 40–80%. These effects appear to be specific to organisms whose growth is inhibited by streptomycin.
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Species Differentiation of Human Vaǵinal Lactobacilli
More LessSUMMARY: The designation ‘Doderlein’s bacillus’ for human vaginal strains of the genus Lactobacillus is vague and unsatisfactory. Thirty-five strains of lactobacilli from twenty-one normal non-pregnant women aged 21–40 were isolated; c. 25 % were heterofermentative. Of 21 isolates studied in detail, 14 were L. acidophilus and two were L. casei var. rhamnosus (Rogosa et al. 1953). The heterofermentative species comprised four strains of L.fermenti and one of L. cellobiosus (Rogosa et al. 1953). Glycogen fermentation, which was found only in certain strains of L. acidophilus, was a variable characteristic. In addition, Leuconostoc mesenteroides, which on examination of smears can be confused with short rod forms, was also isolated.
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