摘要:

Five amino acids, isoleucine, leucine, phenylalanine, tryptophan, and valine, specifically and individually repressed the formation of the extracellular protease ofStreptococcus faecalisvar.liquefaciens. Neither the protease itself, nor the synthesis of β-galactosidase, nor the growth of the organism was affected adversely by the presence of these amino acids. Several di- and tri-peptides containing these inhibitory amino acids also specifically repressed proteinase biosynthesis.Proline is involved in the feedback inhibition of the protease.

ISSN:0008-4166    

DOI:10.1139/m68-212

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Electron micrographs of sectioned spheroplasts ofD.aestuariihave shown spontaneous spheroplast formation to be initiated by a separation of the cell wall to form an external projection or bleb. The transition to spheres occurs 4 to 6 days after exponential growth, is preceded by loss of sulfate-reducing ability, osmotic sensitivity, and viability, and is temperature dependent.

ISSN:0008-4166    

DOI:10.1139/m68-213

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Several strains ofS.aureuswere induced with mitomycin C, a radiomimetic drug, and the results do not offer direct support for a general explanation for alpha toxin synthesis based upon various aspects of lysogeny. Data are also presented showing that toxin is generated intracellularly and continually released into the medium. Small alkaline changes in pH by the metabolizing culture, not affecting growth, are sufficient to stop or greatly inhibit toxin synthesis. In an actively growing culture, this phenomenon appears as a sharp rise in intracellular toxin synthesis, followed by a peak and then decline, even though the culture continues to grow and increase in optical density. Because the toxin molecule is stable at normal cultural pH values, an alkaline pH may interfere with toxin synthesis at the intracellular level.

ISSN:0008-4166    

DOI:10.1139/m68-214

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Effect of the soil-applied herbicide atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) on growth activity ofSclerotium rolfsiiandTrichoderma viridewas determined in soil culture. The fungi were grown axenically in flasks of sterilized soil containing 0, 8, 20, 40, 80 μg of atrazine per gram of soil, and CO2evolution was measured at intervals over a period of 19 days for the pathogen and 14 days forT.viride. ForS.rolfsii, maximum CO2-carbon was produced in soil with 8 μg of atrazine, this being significantly above the O-herbicide control. Higher concentrations greatly inhibited activity of the pathogen. Correlation coefficients revealed that total production of CO2-C was closely related to amount of NO3-nitrogen consumed and titratable acidity produced (mostly oxalic acid); soil pH decreased with increased activity of the fungus.T.viridegrew very rapidly in all treatments, activity being most accelerated between 3 and 10 days after inoculation. Production of CO2-C for all treatments above 8 μg indicated a stimulatory effect upon this fungus. Economic coefficients relating total CO2-C to amount of NO3-N consumed were highest for the 80-μg atrazine treatment and declined with decreasing concentration. Soil pH increased from an initial value of 6.4 to 7.4, with no significant differences between treatment.

ISSN:0008-4166    

DOI:10.1139/m68-215

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A fungistatic principle produced by a bacteriumPseudomonassp. was isolated, characterized, and its potential role in soil fungistasis considered. The principle was isolated from a concentrated cultural filtrate of the bacterium by the use of column chromatography, and characterized by its solubility and elemental analysis and by infrared, nuclear magnetic resonance, and mass spectra. The fungistatic principle was an unsaturated, aliphatic, hydroxyketone with a molecular weight of approximately 166. This compound could be recovered from soil only with organic solvents and, therefore, it was concluded that the principle probably does not contribute to soil fungistasis.

ISSN:0008-4166    

DOI:10.1139/m68-216

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Spores from three different strains ofBacillus anthraciswere examined by electron microscopy for the presence of a hair-like nap previously reported to be present on the exosporium of spores of the Sterne strain (avirulent). In addition to that strain, the Vollum strain (virulent) and a rough, avimlent variant of the Vollum were utilized in the current studies.Spores were fixed with Kellenberger's standard OsO4fixative and embedded in Maraglas. Thin sections were poststained with various combinations of the following: potassium permanganate, uranyl acetate, lead citrate. The nap on the exosporium of spores of the Sterne strain was revealed most clearly when thin sections were poststained with all of the aforementioned stains. Post-staining by a single application of any of the three reagents resulted in a nap that was barely perceptible.The surface of the exosporium of spores from the Vollum strain and the rough, avirulent variant was found to be quite different from that of the Sterne strain. On the two former, the surface layer is approximately one-third as thick as the layer of hairs in the nap on the latter.

ISSN:0008-4166    

DOI:10.1139/m68-217

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Samples of marine sediment from the western equatorial Atlantic and Caribbean and from the Peru Current area of the Pacific were examined for Clostridia. Samples of sediment from the Peru Current area contained more species of Clostridia, especially saccharolytic species. Six virulent strains ofClostridium novyiand 14 strains ofClostridium perfringenswere isolated from the samples of sediment from the Peru Current area, although none was isolated from sediment samples from the Atlantic and Caribbean. Sediment samples from the latter area contained a higher proportion of frankly proteolytic and amino acid utilizing clostridia.

ISSN:0008-4166    

DOI:10.1139/m68-218

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

A study of interferon yield in cell cultures prepared from a variety of chick embryo organs exposed to three strains of influenza type A virus showed that both virus and cells differed in their capacity to induce and produce interferon. The WS strain of virus was superior to the PR8 and NWS as an interferon inducer, and cell cultures prepared from chick embryo lung produced higher titers of interferon than did cells from other organs.

ISSN:0008-4166    

DOI:10.1139/m68-219

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Six cultures ofEchinostelium minutumwere isolated from dead grass. Single spores and myxamoebae of these isolates produced protoplasmodia and sporangia; hence there was no indication of the presence of a mating-type factor. One isolate, D-3, was established in monoxenic culture withAerobacter aerogenesand used for subsequent studies. Myxamoebae grown in a dilute glucose – peptone – yeast extract broth had a minimum generation time of 13 h. Conversion of myxamoebae into swarm cells occurred in a liquid environment at a rate independent of the concentration of myxamoebae between 1 × 105–1 × 106 cells/ml. Protoplasmodia, which multiplied by binary fission, had a minimum generation time of 12 h on Ionagar No. 2. Maximum conversion of protoplasmodia into fruiting bodies was produced by subculture to Ionagar No. 2, with approximately 100% conversion being obtained within 48 h. Nearly 100% of the spores were viable if the sporangia matured in the absence of bacterial growth.

ISSN:0008-4166    

DOI:10.1139/m68-220

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Entamoeba histolytica(DKB strain) antigen mixed with an equal volume of complete Freund's adjuvant was injected at multiple sites into three rabbits. Primary response sera were drawn 1, 2, and 3 weeks after the first injection. Two injections of antigen were given in the fourth week, at 3-day intervals. The secondary response sera were drawn 5, 6, and 12 weeks after the beginning of immunization. A steady hemagglutination (HA) titer of 1:128 was obtained with all the three primary response sera, while the secondary response sera showed HA titers of 1:2000 to 1:8000. The 0.1 M 2-mercaptoethanol treatment of these sera reduced, but did not completely obliterate, their HA activity. The HA activity was detected in both the pooled γM and γG classes of immunoglobulins of the primary and secondary response sera; the immunoprecipitating activity was confined to the γG class. 2-Mercaptoethanol treatment completely destroyed the antibody activity of γM fractions without affecting that of the γG fraction. Repeated immunoelectrophoresis runs of the whole sera and pooled γM and γG fractions showed variable numbers of precipitin bands at the γG position but none at the γM and γA positions.

ISSN:0008-4166    

DOI:10.1139/m68-221

出版商:NRC Research Press    

年代:1968

数据来源: NRC