摘要:

Cellulase (Cx) synthesis was inducible byPyrenochaeta terrestrisin liquid culture. Cellulase activities on various types and amounts of cellulose reached specific maximum plateaus which were maintained indefinitely. These plateaus were reestablished when the enzyme was diluted at each substrate concentration. The maximum levels appeared related to rates of cellulolysis. Above a low threshold rate of hydrolysate liberation, maximum Cx levels are ordered inversely to cellulolytic rates. Supplementing the inducer cellulose with glucose or related compounds above 5 × 10−4 Mrepressed synthesis nearly to the basal level. The evidence lends credence to a hypothesis that Cx synthesis byP.terrestrisis regulated by an inducer:repressor mechanism.

ISSN:0008-4166    

DOI:10.1139/m66-030

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

A soil-borne myxobacter identified as a species ofSorangiumproduced a potent antibiotic capable of inhibiting growth of a wide variety of microorganisms including Gram-positive and Gram-negative bacteria, fungi, actinomycetes, and yeasts. The active material was readily isolated from culture fluids of the organism by ether extraction or by adsorption on a resin. A high degree of purity was achieved chromatographically. Acetone, methanol, or aqueous solutions of the antibiotic were stable when stored at low temperature (4 °C). At 70 °C it was unstable in phosphate buffer but retained its activity in iris buffer at neutral and alkaline pH.

ISSN:0008-4166    

DOI:10.1139/m66-031

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Hemolysin is formed in sonic extracts of cells ofPseudomonas aeruginosaby the action of a heat-labile substance, probably an intracellular "release" enzyme, on a substrate from the disrupted cell. The substrate and most of the hemolysin released can be sedimented by high-speed centrifugation. Hemolysin-negative strains appear to possess no release enzyme but do contain the substrate since addition of particulate matter to extracts of hemolysin-positive cells increases the rate and extent of hemolysin formation. The rate of hemolysin release in sonic extracts is strongly influenced by the concentration of the two reactants, and minor dilution abolishes all activity. There is only a small amount of release enzyme and substrate present in 24-h cells but increasingly greater amounts appear in extracts of 48- and 72-h cells. The hemolysin-forming system is sensitive to heat and is inactivated in 2 min at 100°. Treatment of particulate matter with lysozyme plus EDTA does not reduce the amount of hemolysin released by subsequent exposure of the particles to the release enzyme present in fresh sonic extract.

ISSN:0008-4166    

DOI:10.1139/m66-032

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Soluble cellular fractions of surface and submerged cultures ofPenicillium cyaneo-fulvum, grown in beef heart infusion (BHI) medium supplemented with glucose, showed well-defined fluctuations in proteolytic activity. Four proteases were shown to occur in the cells, and fluctuations in protease specific activity were considered to be related to the appearance and disappearance of individual enzymes. Synthesis of these enzymes seemed to be regulated by the pH of the external medium.Several proteases also occurred in filtrates of cultures grown in BHI–glucose medium. A comparison of intra- and extra-cellular alkaline proteases (optima, pH 10) showed that, although they were similar in many respects, the enzymes could be distinguished by their action on polyamino acids. Inability to detect the extracellular alkaline protease in cell preparations suggested that this enzyme was released into the medium as rapidly as it was produced.

ISSN:0008-4166    

DOI:10.1139/m66-033

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The effect of heat on the O and B antigens ofEscherichia coliserotype O26:B6 was studied. Aliquots of cell suspensions containing 1.5 × 1010 cells/ml were heated at 55, 65, 75, 85, and 100 °C, respectively, for 1 hour. The heated cells were centrifuged and the precipitinogen titer determined using O and OB antisera. The supernatants from cell suspensions heated at the higher temperatures contained proportionately more of the soluble antigen than those heated at the lower temperatures.Gel diffusion tests of the supernatants showed that both O and B antigens were released when cells were heated. Mild acid hydrolysis of a supernatant increased the B reactivity of that supernatant and slightly enhanced the O reaction. It was concluded from this study that the O and B antigens exist as a molecular complex; heating releases the B component from the complex and causes the increased agglutination with O antiserum.

ISSN:0008-4166    

DOI:10.1139/m66-034

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Spheroplast induction and lysis of 6 BCG strains ofMycobacterium tuberculosisby glycine and lysozyme was studied in various media. Spheroplast production was noted in only three strains involving 20% of cell populations. Lysis, as distinct from spheroplast induction, occurred in Dubos medium containing 1.5% glycine and 0.01% lysozyme after 24–48 hours of incubation. Estimation from a standard curve indicated 40 to 70% lysis of the total cell population after 7–10 days of incubation.Similarly, lysis of BCG cells occurred when the inducers, glycine, lysozyme, and lithium chloride, were added to nitrogen-starved cultures grown in Aldridge synthetic medium for 7 to 8 days.

ISSN:0008-4166    

DOI:10.1139/m66-035

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The cell wall of Gram-negative bacteria is generally complex and multilayered. Many, exemplified byEscherichia coliandSpirillum serpensin this study, show a constrictive division in which die cell appears to be pinched in the middle and septa are not seen. It was found that sections ofE.coliandS.serpensshow true septum formation in a high proportion of dividing cells when they were grown and fixed at 45°. Cells grown at 45° still showed some septum formation if cooled to 20° before fixation. However, septa were demonstrated in cells grown and fixed at 30° when the buffer used in the Ryter and Kellenberger fixative was diluted 1:6; it would appear that the tonicity of the fixing environment is critical. These septa involve an annular invagination of the plasma membrane and the concomitant synthesis of an extremely thin cell wall septum, which appears to consist of the mucopeptide layer alone. Centripetal splitting of this layer and synthesis of the outer layers of the wall follow but are sufficiently delayed that a complete septum was often visible. This form of septum has been known as the normal habit fur some and can now be considered normal for most, if not all, Gram-negative bacteria. The reason for the appearance of constriction in dividing cells fixed by commonly accepted methods remains obscure but attention is drawn to the problems of artefact in the preservation and study of dynamic structures at high resolution.

ISSN:0008-4166    

DOI:10.1139/m66-036

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

The minimal requirements for a synthetic medium capable of supporting adequate growth ofAgrobacterium tumefacienswere found to beD-glucose, urea, phosphate, and magnesium salt.D-Ribose,D-fructose, andD-xylose could be used to replaceD-glucose.When the organism was grown on the above medium, the addition of any one of the pyrimidines or pyrimidine ribosides, uracil, cytidine, uridine, or orotic acid resulted in the extracellular accumulation of pseudouridine. From the data presented it is clear that conversion to uracil took place in all cultures before pseudouridine was formed.

ISSN:0008-4166    

DOI:10.1139/m66-037

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Five strains ofRhizobium melilotiserially cultivated on a basal yeast water mannitol mineral salts medium supplemented with increments of nine amino acids, respectively, produced ellipsoidal, bacteroidal, and elongated cell forms. Colonies produced on media containingD-amino acids and glycine were smaller and less opalescent than were those on the basal medium. Growth of two strains on media supplemented with theL-isomers of alanine, histidine, and phenylalanine, respectively, exceeded that in media to which theD-isomers of these amino acids were added. Growth was negative or sparse in the basal medium supplemented with 0.075%L-cysteine. Serial cultivation in media containing increments ofD-cysteine,D-alanine,D-phenylalanine, and glycine produced the maximum loss in nitrogen-fixing ability;L-alanine andL-histidine were the least deleterious. Four strains became ineffective after serial cultivation on at least two of the nine amino acid media. The infective and nitrogen-fixing properties of an ineffective strain were unchanged after cultivation in amino acid supplemented media.

ISSN:0008-4166    

DOI:10.1139/m66-038

出版商:NRC Research Press    

年代:1966

数据来源: NRC

摘要:

Guanofuracin, a nitrofuran compound used for the selective enrichment ofListeria monocytogenes, was observed to be inactivated by cultures ofL.monocytogenes.L.monocytogenes, in mixed culture, appeared to protect other organisms from the inhibiting action. Supernatant fluids ofL.monocytogenescultures inactivated guanofuracin to a great extent, but neutralization to pH 7.2 removed this activity. No specific guanofuraein-inactivating substance could be detected inL.monocytogenescultures, Autoclaving (20 minutes at 121 °C) caused partial (60%) destruction of the drug. The antibacterial activity of guanofuracin largely depended upon the pH of the incubation medium, being high in alkaline pH and low in acidic pH. The inactivation in acidic pH can be reversed by adjusting the pH to the alkaline side. The presence of the drug in the medium caused a prolongation of the lag phase but no change in the rate of growth, once established.L.monocytogenesrapidly developed resistance to guanofuracin in proportion to the concentration to which the organism was exposed.

ISSN:0008-4166    

DOI:10.1139/m66-039

出版商:NRC Research Press    

年代:1966

数据来源: NRC