摘要:

Spectrophotometric methods were used to study the activity of the leucine naphthylamidases ofParamecium caudatum. Optimum activity of the enzymes occurred from pH 6.6 to 6.8 and was enhanced by either Co2+, Mn2+, or by Mg2+. Maximum activity occurred when Co2+was used with either Mg2+or Mn2+. Activity was depressed by either Sr2+, Fe2+, Zn2+, Ni2+, Hg2+, Cd2+, Pb2+, Sn2+, or Li2+, and not affected by Ba2+, Cu2+, and Ca2+. Approximately 40% of the enzymatic activity was inhibited by EDTA. Most of this inhibition was reversed by either Mg2+, Co2+, or Mn2+.

ISSN:0008-4166    

DOI:10.1139/m67-157

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The inactivation of a canine adenovirus hemagglutinin and infectivity at 56 °C at varying times up to 1 h has been studied in the presence of various ions and concentrations of ions.Under conditions of uncontrolled pH 1–2 MNaCl and MgCl2both stabilized the virus hemagglutinin and infectivity. Lower concentrations of these salts as well as 0.04 Mphosphate, Hank's balanced salt solution, and minimal Eagle's medium had little stabilizing effect. Molar concentrations of phosphate and Tris butter were also found to stabilize the virus hemagglutinin.The pH adjustment of the suspending salt solution was found to be important since high concentrations of salts such as MgCl2are quite acidic. Both 1 MMgCl2and 1 MNaCl stabilized the virus in the pH range of 4–6, but inactivation was rapid at pH 3 and less rapid at pH 7. Ion concentrations lower than 1 Mmarkedly reduced the hemagglutinin stabilization at optimun pH.

ISSN:0008-4166    

DOI:10.1139/m67-158

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Stained bacteria were observed on the surface of bleached leaves. On most plants in Puerto Rico, bacteria were absent during dry weather and were found in varying numbers with the onset of a rainy period. In Ohio, there were a few or no bacteria on leaves of crop plants sampled at different times during the growing season. Drops of sterile water were placed on individually boxed leaves of field cucumber plants that were brought to the laboratory. Areas of leaves that had been covered by drops for 24–72 h carried sizable populations of bacteria. On adjacent leaf areas not covered by drops and subjected to a high relative humidity, bacteria were absent or few. Similar results were obtained in the laboratory with boxed, detached leaves from field-grown plants. We conclude, therefore, that a probable reason for the sparsity of epiphyllous bacteria in Ohio is that free water usually does not remain on leaves for a long enough time to permit the formation of significant bacterial populations.

ISSN:0008-4166    

DOI:10.1139/m67-159

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

An α-amylase fromThermoactinomyces vulgarishas been purified about 100-fold. Its optimum pH was between 5.9 and 7.0, and the maximum rate was achieved at 60 °C. In the absence of substrate, the enzymes were more stable at pH 5.9 than at higher or lower pH values; inactivation was rapid at pH 7.0. Temperatures of 70 °C or greater also caused rapid denaturation of the enzyme in the absence of substrate. Three major peaks of amylase activity were detected when purified enzyme preparations were passed through Sephadex G-75 columns. At least two of these amylases were interconvertible. Four or fiveT.vulgarisproteinases also were separated, using ion exchange column chromatography.

ISSN:0008-4166    

DOI:10.1139/m67-160

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The glucose dissimilation of a marine pseudomonad was investigated using manometric techniques as well as glucose specifically labelled at different sites. Data from radiorespirometric procedures indicated that some 90% of the glucose catabolized was routed through the Entner-Doudoroff pathway. The observed differences between the amount of carbon assimilated and the amount catabolized were discussed in relation to the heterotrophic uptake method which is currently being applied to problems in aquatic microbial ecology.

ISSN:0008-4166    

DOI:10.1139/m67-161

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Environmental factors affecting the reduction of selenite by growing and resting cells ofStreptococcus faecalisN83 andStreptococcus faeciumK6A, respectively, were studied. Both organisms displayed an intrinsic capacity to reduce selenite to the metallic selenium in a complex medium. However, concentrations of selenite above 50 μg/ml proved toxic toS.faecium, whileS.faecalistolerated and reduced selenite at concentrations as high as 1000 μg/ml. The pH optimum for selenite reduction lay between 7.2 and 7.7 for both organisms. Though maximum selenite reduction was shown by both under anaerobic conditions,S.faecalis, but notS.faecium, reduced selenite substantially even under aeration. The reduction of selenite byS.faecalisdid not appear to be directly conditioned by the oxidation-reduction potential of the medium; a low potential was, however, necessary for the reduction of selenite byS.faecium. The presence of a flavin compound was associated with maximum reduction of selenite byS.faecalis, but effected no change in selenite reduction byS.faecium. The growth of these organisms could not be coupled to the reduction of selenite.

ISSN:0008-4166    

DOI:10.1139/m67-162

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Cell-free extracts ofStreptococcus faecalisN83 andStreptococcus faeciumK6A were shown to possess comparable enzyme systems for the reduction of selenite to metallic selenium. The enzymatic complement of each of the organisms was oxygen sensitive, heat stable, and required flavin adenine dinucleotide (FAD) for maximum stimulation. Potent reduced nicotinamide adenine dinucleotide (NADH2) oxidase activity was demonstrated in extracts of both organisms. Although the NADH2oxidase ofS.faeciumwas sensitive to sulfhydryl inhibitors, the enzyme inS.faecaliswas unaffected. The addition of ascorbate to the medium reversed the inhibitory effects of selenite and enhanced selenite reduction byS.faecium. Radioisotope studies, utilizing selenium75, demonstrated that selenite was taken up by both test organisms. The addition of ascorbate increased the rate and extent of selenium75incorporation. It was concluded that the inhibitory effect of selenite and the inability ofS.faeciumto reduce the ion is a reflection of the oxidation by selenite of sulfhydryl groups on the active site.

ISSN:0008-4166    

DOI:10.1139/m67-163

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Goat milk was obtained from the right lactiferous sinus following instillation of PR8 influenza type A virus. The proteins precipitated from goat milk serum by (NH4)2SO4were found to contain antibody activity and further purification was undertaken. In the development of the method the protein solutions were subjected to paper chromatography and paper and polyacetate high voltage electrophoresis, both before and after a number of isolation and purification steps. In addition, preparations from each step were run on the Technicon amino acid analyzer for the presence of amino acids and (or) peptides.As a working procedure, a preparation obtained after cold acetone precipitation was subjected to rivanol treatment, and after electrophoresis a single protein band containing the antibody was obtained. This material was further purified by gel filtration using a Bio-Rad P150 column. The antibody containing protein was finally isolated in the eluate by a fraction collector using phosphate buffer as the eluting fluid. There was excellent recovery of the antibody activity in each preparation.

ISSN:0008-4166    

DOI:10.1139/m67-164

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Separate extracts ofNeuorospora crassagrown either in Vogel's medium N, medium N + glutamate, or medium N which had been made deficient in zinc, were assayed for succinic dehydrogenase and soluble protein at intervals throughout the asexual cycle. Succinic dehydrogenase, although apparently unnecessary for either the formation of conidia or conidial germination, does appear to be necessary for mycelial growth and for the production of conidiophores. Differences in the amount of enzyme during morphologically distinct states of differentiation (i.e. production of the germ tube and production of the conidiophore) may serve as an indicator of significant changes in the physiology ofNeurosporaat these times during development.The level of succinic dehydrogenase in the conidiophore before its differentiation into conidia appears to influence the amount of this enzyme found in the conidia. This is in keeping with the idea that conditions prevailing in the cytoplasm before the formation of conidia may directly influence the constituents subsequently found in the conidia which determine conidial viability, rate of germination, and growth yield.

ISSN:0008-4166    

DOI:10.1139/m67-165

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

"Malic" enzyme has been isolated fromNeurospora crassawhich can bring about the reversible carboxylation of pyruvic acid. The enzyme is specific toL-malate and NADP and is activated by Mn++and Mg++. The partially purified enzyme does not decarboxylate oxaloacetate but is competitively inhibited by it. This enzyme is synthesized only during the early stages of the growth cycle and is repressed by acetate. In addition, the oxidative decarboxylation of malic acid is competitively inhibited by aspartic acid; the degree of inhibition depends upon the cell growth phase from which the enzyme is extracted. "Malic" enzyme isolated from a 12-h culture is not significantly inhibited by aspartate. However, this inhibition increases to 90% if an enzyme preparation from a 24-h culture is used. The significance of enzyme repression by acetate and the inhibition of the activity by aspartate are discussed.

ISSN:0008-4166    

DOI:10.1139/m67-166

出版商:NRC Research Press    

年代:1967

数据来源: NRC