摘要:

A mutation in a gene inNeurospora crassaleading to a semicolonial growth pattern and a deficiency of NADP-specific glutamate dehydrogenase is reported. The NAD-specific enzyme is not affected. The mutants (referred to asam-morphs) do not show any nutritional requirement nor is the growth pattern altered by addition of supplements in the medium. Addition ofL-alanine,L-glutamate, and other α-amino acids to the medium does not result in an appreciable increase in specific activity of the NAD-specific glutamate dehydrogenase. This is due to the inability of amino acids to induce the NAD-specific enzyme, a phenomenon known to occur in the familiarammutants. A spontaneous revertant of one of these mutants shows a mycelial morphology together with a normal glutamate dehydrogenase.The behavior ofam-morphsis discussed in relation to other amination-deficient, mycelial mutants.

ISSN:0008-4166    

DOI:10.1139/m68-103

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Polygalacturonase has been postulated as being involved in the invasion of the host legume byRhizobiumspp. The role of this enzyme in the invasion ofGlycine maxbyRhizobium japonicumwas investigated. Enzyme activity of severalRhizobiumspp. was assayed viscometrically and no constitutive polygalacturonase was found. The enzyme could not be induced by growth with either pectin or galactose as the sole carbon source. Extract and exudate from the roots of nodulating and nonnodulating strains ofGlycine maxthat had been incubated with effective strains ofR.japonicumfailed to show any higher levels of polygalacturonase activity than did uninoculated control plants. Previously reported experiments were duplicated. Levels of polygalacturonase activity from the extract and exudate of white clover inoculated withR.trifoliiCl 226 were as reported in the literature. Contrary to published reports, however, no greater levels of enzyme activity were found from effective plant–bacteria associations than from either ineffective associations or uninoculated control plants. It was concluded from these experiments that polygalacturonase does not play a major role in the invasion ofGlycine maxbyRhizobium japonicum.

ISSN:0008-4166    

DOI:10.1139/m68-104

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Pseudomonas aeruginosafailed to accumulate carbohydrate, lipid, including poly-β-hydroxybutyrate, or polyphosphate when grown under conditions normally favorable for the deposition of these reserve materials. Washed cell suspensions prepared from cultures grown under conditions of limiting nitrogen, limiting carbon, or excess of both exhibited immediate and linear production of ammonia when starved. When glucose-U-14C was added to a 24-h-culture, growing in a nitrogen-limited medium, the radioactivity was largely recovered in keto acids which accumulated in the growth supernatant. Exhaustion of the limiting nutrient during growth resulted in the degradation of ribosomes regardless of whether the nutrient was the carbon or nitrogen source.

ISSN:0008-4166    

DOI:10.1139/m68-105

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Late stationary phase cultures ofPseudomonas aeruginosawere found to be very susceptible to cold-shock during harvesting. Washing in cold buffer caused a sudden decrease in the number of viable cells and a persistent release of intracellular enzymes. The phenomenon was characterized by an increased oxygen uptake and an initial absence of extracellular ammonia during the respiration of washed cell suspensions. The presence of oxidizable substrates in the supernatant fluid accounted for these observations. A partial inhibition of the release of intracellular materials was afforded by the addition of magnesium ions to the washing and suspending buffer. There was an increased sensitivity of cells to cold-shock with age.

ISSN:0008-4166    

DOI:10.1139/m68-106

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The viability of suspensions ofPseudomonas aeruginosa, prepared from 48-h cultures, grown in either a nitrogen-limited or carbon-limited medium, decreased 25% during 48-h of endogenous respiration, whereas the viable numbers of 48-h cells harvested from a complete medium increased 57% during the early stages of endogenous respiration and remained constant thereafter. In all endogenously respiring cell suspensions, ribonucleic acid and protein decreased by similar amounts and deoxyribonucleic acid increased. Glucosamine was not found to decrease to a significant degree during starvation. Constitutive enzymes and (or) the cofactors involved in the oxidation of glucose were found to diminish with progressive starvation. Starvation severely depleted the ribosome complement of the cells; however, the starved cells were able to synthesize a permease for α-ketoglutarate. The addition of an exogenous substrate brought about the reincorporation of endogenously liberated ammonia and of 260 mμ absorbing material with a concurrent synthesis of 50S ribosomes.

ISSN:0008-4166    

DOI:10.1139/m68-107

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

DNA extracted from two mycobacteriophages have been shown to be infective for three different strains of mycobacteria during their multiplication in liquid medium. The infection resulted in a modification of the phage genome. A study of the plaque morphology, host range, heat resistance, efficiency of plating, and neutralization rate showed significant differences between the donor phage and the phage progeny.

ISSN:0008-4166    

DOI:10.1139/m68-108

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The effect of soil:water ratio and autoclaving time on the efficiency of organic carbon extraction from soil was evaluated, and a method was developed for the routine preparation of freeze-dried soil extracts of standardized carbon contents. The optimum soil:water (w/v) ratio chosen for soil extract preparation will depend on the water-holding properties of the soil and on the subsequent use of the extract; a ratio of 1:3 to 1:5 appears optimum for preparation of freeze-dried extracts; efficiency of carbon recovery decreases drastically at ratios of less than 1:2 to 1:3. From an efficiency standpoint longer autoclaving times will yield substantial increases in organic carbon, with the most marked increase occurring within the first hour. No major differences in numbers of soil microorganisms developing on agar media prepared from diverse extracts were observed as long as the pH (6 to 7.5) and carbon content (0.1 to 2.6 g/1) of the extracts were within the normal range for soil extracts used for microbial media.

ISSN:0008-4166    

DOI:10.1139/m68-109

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

Growth-inhibitory activities of some or all of 98 1,4-naphthoquinones and 16 related compounds onEscherichia coliand two strains ofStaphylococcus aureuswere determined alone or in combination. These values, when plotted against their polarographic half-wave potentials and those of their C2-n-butylthio analogs support the hypothesis that these compounds, or the products resulting from their reaction with a protein nucleophile, function by short-circuiting one or other of the quinones present in the electron-transport chain.

ISSN:0008-4166    

DOI:10.1139/m68-110

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

After addition of mitomycin C toPseudomonas aeruginosastrain MAC-264 cells, DNA synthesis stops but resumes again after 45 min. This resumption in DNA synthesis is due to the induction of a temperate phage. Early after induction, both RNA and protein syntheses continue but later on little or no net synthesis of these macromolecules occurs. Cell lysis occurs at 90 to 105 min after addition of mitomycin C. Analysis of the lysates indicates that a DNA phage with an icosahedral head about 55 mμ in diameter with a short wedge-shaped tail is produced. This phagehas a buoyant density of 1.468 g/ml in CsCl. The guanine + cytosine content of the phage DNA determined by its buoyant density in CsCl is 46% compared to 68% for the host DNA.Some phage tail-like structures which have a buoyant density of 1.305 g/ml in CsCl are also induced at the same time.

ISSN:0008-4166    

DOI:10.1139/m68-111

出版商:NRC Research Press    

年代:1968

数据来源: NRC

摘要:

The properties of glycine-induced spheroplasts of six pathogenic serotypes ofE.coliwere investigated. Fimbriae and flagella appeared to be only partially synthesized as was the somatic O antigen. Cytopathogenicity of these spheroplasts for tissue culture was reduced and the infection of the monolayers was retarded as compared with the normal bacillary forms. Sensitivity to phage was almost completely lost, suggesting that glycine had either interfered with the synthesis of phage receptors or had altered the mucopeptide layerwhich is the substrate for phage enzymes. Alternatively, the phage may become a prophage inside the spheroplast with the loss of virulence.

ISSN:0008-4166    

DOI:10.1139/m68-112

出版商:NRC Research Press    

年代:1968

数据来源: NRC