- Volume 53, Issue 1, 1968
Volume 53, Issue 1, 1968
- The Society For General Microbiology
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- Article
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Microbicidal Action of Compounds Generated by Transient Electric Arcs in Aqueous Systems
More LessSUMMARY: Submerged electrical discharges between copper-containing electrodes rendered the treated liquid microbicidal. Part of this activity was unstable and decreased rapidly during the first few minutes. It might have been caused by cuprous ions or substances with oxidative activity. The stable microbicidal activity was due to copper released from the electrodes. This copper existed only partly in ionic form. Inorganic salts and most organic substances tested decreased the bactericidal effect of discharge-treated water. Such substances also diminished the protracted killing effect which was observed when bacteria suspended in water of relatively high purity were subjected to transient electric arcs.
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Ploidy Level in the True Slime Mould Didymium nigripes
More LessSUMMARY: Estimation of chromosome numbers in approximately 1000 nuclei of amoebae and plasmodia of the true slime mould, Didymium nigripes, has shown that in the c6 and s3 strains the ploidy level of amoebae and plasmodia is the same. Nuclei with differing chromosome numbers were found in the populations studied. The data collected here are consistent with the hypothesis that as a culture ages during serial subculture of one stage of the life-cycle, nuclei with higher than normal chromosome numbers accumulate.
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Observations on the Differentiation of Plasmodia into Fruiting Bodies by the True Slime Mould, Didymium nigripes
More LessSUMMARY: Under defined experimental conditions plasmodia of Didymium nigripes began to differentiate into fruiting bodies 16-18 hr after transfer to bacteria-free agar. The process has been divided into a number of easily recognizable stages and the duration of each stage determined. Plasmodia lost ability to continue vegetative growth at a time before the actual fruiting bodies began to form.
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Lysis of the Limiting Membrane of Mycoplasma gallisepticum by Chemical Agents
More LessSUMMARY: Lysis of Mycoplasma gallisepticum by various chemical reagents and enzymes was examined. Lysis was measured by determining the release of intracellular constituents, and compared with the results obtained by the turbidimetric method. The ultracentrifuge was used to compare solutions of isolated membrane in 2-chlorethanol, phenol + acetic acid + water mixture, aqueous urea, and aqueous sodium lauryl sulphate, all of which readily dissolved membranes and whole organisms.
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Protease Production by Bacteroides amylophilus Strain H 18
More LessSUMMARY: Bacteroides amylophilus strain H 18 produced protease(s), active at pH 7.0, when grown anaerobically in a simple maltose, ammonium sulphate, cysteine, sodium bicarbonate and salts medium. Protease production was neither induced nor repressed by a wide range of nutrients. Protease was synthesized by exponentially growing organisms and 20% of it was liberated into the growth medium. The cell-bound protease was completely accessible to the protein substrate. Protease production was proportional to ammonium sulphate and maltose concentration in the ranges in which these nutrients were growth limiting.
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The Protease Liberated from Bacteroides amylophilus Strain H 18 by Mechanical Disintegration
More LessSUMMARY: Disintegration of lyophilized Bacteroides amylophilus H 18 suspended in water, by agitation with glass beads, gave an extract containing 40% of the total cell protease activity. Better yields of an esterase which hydrolysed p-toluenesulphonyl-L-arginine methyl ester (TAME) were obtained by disintegration in 0.1 M-phosphate buffer (pH 7.0). Ultrasonic disintegration of fresh suspensions was used to obtain larger quantities of cell extract. The protease had a broad plateau of activity between pH 5.5 and 9.5; the esterase had maximum activity at pH 8.0. Divalent cations had relatively little effect on either activity but 5 × 10−3 M-CaCl2 restored activity to EDTA-inhibited esterase. The protease was not inhibited by EDTA. Both activities were inhibited by di-isopropylphosphofluoridate but the protease was incompletely inhibited (87%). Neither activity was activated nor inhibited by thiol reagents. In addition to TAME, N-α-benzoyl-L-arginine methyl ester (BAME), N-α-benzoyl-L-arginine ethyl ester (BAEE), N-α-benzoyl-DL-arginine-p-nitroanilide and lysine ethyl ester were hydrolysed, indicating a trypsin-like specificity. The esterase differed from trypsin in not hydrolysing N-α-benzoyl-L-arginine amide (BAA) nor N-α-benzoyl-DL-arginine-naphthylamide (BANA) and in hydrolysing BAME more rapidly than TAME. There was some hydrolysis of N-α-benzoyl-L-leucyl-2-naphthylamide and some amino peptidase activity as shown by the hydrolysis of L-analyl-2-naphthylamide, L-leucylglycine and L-leucinamide. TAME competitively inhibited at least 64% of the protease activity. The K m for casein was 0.17% (w/v). Casein at concentrations greater than 3.0% (w/v) caused substrate inhibition. The rate of ‘tyrosine’ liberation was proportional to protease concentration provided that less than 0.5 mg. ‘tyrosine’ was liberated from the 80 mg. casein in the standard assay. Protease concentration to the power 2/3 or the power 1/2 was proportional to the rate of hydrolysis but the straight line did not go to the origin.
Bacteroides amylophilus H 18 extracts contained much nucleic acid which could not be separated from the protease activity by ammonium sulphate, protamine sulphate nor manganese chloride precipitation. Continuous electrophoresis was also ineffective. Ion-exchange chromatography separated the nucleic acids, but the protease activity was scattered in so many fractions that the purification was only three-fold and the recoveries poor.
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Deoxyribonucleic Acid Base Composition and Taxonomy of Thiobacilli and some Nitrifying Bacteria
More LessSUMMARY: The DNA base composition of 14 authentic strains of the genus Thiobacillus, determined by caesium chloride density gradient centrifugation, was found to vary from 51 to 68 mole % guanine+cytosine (G + C). The mole % G + C values for the various species are as follows: T. thiooxidans and T. concretivorus 51-52, T. neopolitanus and T. ferrooxidans 56-57, and T. thioparus, T. thiocyanoxidans, T. denitrificans, T. novellus and T. trautweinii 62-68. Another group of chemoautotrophic bacteria, the nitrifiers Nitrosomonas europaea and Nitrobacter agilis, were found to have a G + C content of 52 and 65%, respectively. The results are compared with other types of taxonomic studies made with these and related bacteria.
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Active Resistance to Apple Scab
More LessSUMMARY: Two partially characterized groups of compounds were isolated from an apple variety (Miller's Seedling) which has polygenic resistance to apple scab. These compounds inhibited germination of conidia of Venturia inaequalis and interfered with pigment production in log-phase cultures of the organism. They were more abundant in varieties of apple resistant to scab than in susceptible varieties, and increased in the leaves of resistant varieties after inoculation with V. inaequalis conidia. When applied to the foliage of a variety of apple normally susceptible to scab these compounds conferred a measure of protection against the disease. The subject of physiological resistance of plants to microbial attack is discussed.
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Laboratory Cultivation of Some Human Parasitic Amoebae
More LessSUMMARY: Cultural conditions and supplementary substances necessary for the laboratory cultivation of some human parasitic amoebae were investigated by using a basal solution containing inorganic salts, citrate and lactate. Three supplementary components were found necessary: starch grains, animal protein (soluble or insoluble) and living bacteria. Restraint of bacterial growth by antibiotics, and of the development of an alkaline reaction (due to pellicle-forming aerobes) by carbon dioxide, improved the amoebic growth. Under these conditions, all the common parasitic amoebae examined, except Ioda-moeba butschlii, were grown and maintained for long periods in laboratory culture.
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Ascus Cytology of Podospora anserina
More LessSUMMARY: The ascus cytology of Podospora anserina (Ces.) Rehm, a secondarily homothallic Pyrenomycete fungus, has been followed under the light microscope from the crozier, through karyogamy and the three nuclear divisions in the ascus (the first two constituting a meiosis and the third a mitosis) to the first spore mitosis and spore maturation. The spindles remain widely separated at division II, during which segregation for mating type is said to occur. After division III, in which the spindles are transverse, the ascus contains four pairs of sister nuclei. The realignment of the nuclei so that two non-sister nuclei are included in each of the four spores is brought about by the movements of the centrosomes or, more likely, of their outer portions. Spore delimitation, which starts from these organelles, appears as a thin cleavage line separating the spore plasm from the epiplasm of the ascus. A mitosis in the spore initial followed by degeneration of one of the four daughter-nuclei in the primary appendage leads to an imbalance in the mating-type factors in the spore. The wall of the mature spore is separable into three layers, the middle one of which is pigmented. The mucilaginous secondary appendage formed at each end of the spore is already present before the primary appendage is cut off.
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Fine Structure of the Wall and Appendage Formation in Ascospores of Podospora anserina
More LessSUMMARY: The ascospores of Podospora anserina (Ces.) Rehm are delimited by a double membrane system. The primary spore wall develops within this, the outer part of the double membrane being pushed out to form the spore membrane and the inner part forming the plasmalemma of the spore. Starting in the middle of the matrix of the expanding primary wall, a secondary wall is laid down and gradually extends to the outer periphery of the spore wall. Later, a thick tertiary wall is formed at the inner side of the secondary wall by blocks of electron-dense material between which channels of the primary wall matrix remain. This is the pigmented layer of the spore wall. On the innermost side of the spore wall, a part of the original primary wall remains.
The primary appendage at the base of the spore arises as part of the spore initial, but, after it has been cut off by a septum, its contents degenerate and it is bounded only by the primary and secondary wall layers. The secondary appendages, formed at the apex of the spore and at the bottom of the primary appendage, are considered to be actively growing processes bounded by the spore membrane.
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Observations on the Chromatinic Bodies of Two Species of the Actinoplanaceae
More LessSUMMARY: The structure and distribution of the chromatinic bodies of two species of the genus Actinoplanes were studied with light microscopy. Results obtained from observation of material stained by the technique of DeLamater (1951), Feulgen (Rafalko, 1946), or Piéchaud (1954), were supplemented by observation of living material. A technique for observing living and stained preparations with phase-contrast or dark-field microscopy gave results far superior to those obtained with bright-field microscopy. Both strains studied had a nearly identical structure and distribution of chromatinic bodies. Colonies consisted of two hyphal types; substrate hyphae and palisade hyphae (Couch, 1950). The chromatinic bodies of the substrate hyphae appeared variously as short rods or as small bands of material that extended across the width of the hyphae. The palisade hyphae contained bodies ranging from dumb-bell shaped structures to multiple entities composed of 3-4 interconnected sub-units. The distal portions contained dense rods of chromatinic material. The chromatinic rods of the palisade hyphae progressed into the sporangium along with the ingrowth of the sporogenic hyphae into the sporangial envelope. Within the sporangium these rods appeared to contract and undergo repeated divisions into smaller subunits; a single subunit was incorporated into each spore. A striking similarity in structure and distribution of the chromatinic bodies was noted between members of the Actinoplanaceae and members of the Streptomycetaceae.
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The Autolysis of Aspergillus flavus in an Alkaline Medium
More LessSUMMARY: The autolysis of Aspergillus flavus subjected to a combined action of a continuous flow of air and mechanical agitation has been studied. We have obtained a degree of autolysis amounting to 85%. The total loss of nitrogen in autolysing mycelium of A. flavus reached 82%, whereas the loss of phosphorus was 90% from the beginning of autolysis. Total carbohydrates were reduced from 524 mg./sample, at 0 day, to 119 mg./sample by the 16th day of autolysis, which represents a loss of 77%. Glucose was the only sugar found in significant amount in autolysing mycelium of A. flavus, being 96% the total loss. The concentration of mannitol decreased to nearly a third at the end of the log phase. The disappearance of this substance during pre-autolysis and autolysis amounted to 97.7% with respect to the maximum weight present at the 8th day of incubation. Fourteen different free amino acids were identified in the mycelium of Aspergillus flavus during the pre-autolytic and autolytic stages of growth. These amino acids increased their content between the 4th and the 6th days of incubation, to the highest concentration observed. Seventy-nine per cent of this maximum amount disappeared by the end of the log phase, whereas 78% of the remainder disappeared from mycelium during autolysis (16 days). From the total amount of bound amino acids in mycelium of A. flavus it seemed that the make-up of the mycelial protein does not undergo great changes in the interval between pre-autolysis and the initiation of the autolytic phase of growth.
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R (Transmissible Drug-resistance) Factors in Salmonella typhimurium: Pattern of Transduction by Phage P22 and Ultraviolet-protection Effect
More LessSUMMARY: R factors from Enterobacter strains isolated outside Japan were transferred to Salmonella typhimurium LT 2 and their resistance traits transduced by phage P 22. Of five fi + factors conferring resistance to tetracycline (Tc), streptomycin (Sm), sulphonamides (Su) and chloramphenicol (Cm), three, one of which conferred also resistance to kanamycin (Km), behaved like previously reported factors in that: Tc was transduced by itself but never with any other trait; all other traits were usually co-transduced; no transductants could transmit resistance by conjugation, even after infection with F'-13 lac. The other two fi + factors, which conferred also resistance to benzylpenicillin (Pn), behaved similarly, except that: Pn was transduced only at a low rate, and was never co-transduced with any other trait; and a few transductants when given F'-13 lac became able to transmit. Four fi − factors, two of type Tc, Sm, Su, Pn and two of type Tc, Su, Pn differed in that: nearly all Tc transductants acquired also all the other traits; Pn was usually co-transduced with the other traits; and some transductants could transmit by conjugation, even without F'-13 lac. The various transductant classes obtained by treatment with P 22 grown on LT 2 carrying both an fi + (Tc, Sm, Su, Cm, Km) and fi − (Tc, Sm, Su, Pn) factor could be accounted for by transduction of fragments of either one or the other of these factors. The sorts of transductants produced by lysates of a strain possessing Tc, Sm, Su, Cm, Km determinants obtained by growing a strain carrying an fi + (Tc, Sm, Su, Cm) factor with one carrying an fi + (Km) factor suggested that the strain carried two fi + factors, not a recombinant factor. Both fi − and fi + factors conferring resistance to benzylpenicillin conferred also resistance to cephalothin and cephaloridine and caused the constitutive production of a β-lactamase, active on both benzylpenicillin and on cephalothin. All four fi − and one of the five fi + factors resembled coll factors in that they protected strain LT 2 against the bactericidal effect of ultraviolet irradiation.
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New Host-strains for the Lysogenic Corynebacterium diphtheriae Park Williams No. 8 Strain
More LessSUMMARY: Investigation of the lysogenicity of seven Corynebacterium diphtheriae PW 8 variants revealed the spontaneous liberation, by these strains, of phage particles active against two C. ulcerans strains (9304 and 298 G) which are sensitive to C. diphtheriae gravis and mitis phages. By this means, phage particles with different host-range activity and morphology of plaques were obtained from the PW 8 strains. Further studies showed that some C. diphtheriae strains which possess the same sensitivity towards gravis and mitis phages showed the same spontaneous liberation of PW 8-carried phages. The newly obtained phages were able to convert to toxinogenesis both C. ulcerans and C. diphtheriae strains.
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Production of Plant Growth Substances by Azotobacter chroococcum
More LessSUMMARY: Cultures of Azotobacter chroococcum strain A6 were grown for 14 days in a nitrogen-deficient mineral medium, the supernatant fluid and bacteria extracted and examined by paper partition chromatography with two solvent systems which separate authentic gibberellin (GA3) and indolyl-3-acetic acid (IAA). Gibberellin-like substances were not detected on the chromatograms examined under ultraviolet (u.v.) radiation, but were detected when chromatograms were cut into ten equal strips representing a sequence of RF values and the eluates tested in dwarf pea and lettuce hypocotyl bioassays. Certain eluates applied to the roots of tomato seedlings also altered the later growth of stems, leaves and flowers. The Azotobacter cultures contained three gibberellin-like substances, of which probably the dominant was one with an RF value similar to that of GA3; the other two were not identified. The average concentration of gibberellin/ml. culture was 0.03 μg. GA3 equivalent. The gibberellins in Azotobacter cultures probably cause the reported effects on plant development and yield when seeds or roots are inoculated with Azotobacter. Plant growth may also be affected by synthesis of further gibberellins in the root zone when the Azotobacter inoculum colonizes developing roots.
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