摘要:

Nitrification inhibitors were investigated in an attempt to establish whether such chemicals actually kill ammonium-oxidizing bacteria (bactericidal action) or whether bacteria remain viable but temporarily incapable of nitrification (bacteriostatic action). In laboratory experiments with nitrifying cultures, nitrification was completely inhibited, but numbers of ammonium-oxidizing bacteria were not significantly affected by a 48-h treatment with 2,6-dimethylbenzoquinone, dicyandiamide, or potassium ethyl xanthate applied at the rate of 100 mg inhibitor/L culture medium or by nitrapyrin at 10 mg/L. However, commercial formulations of etridiazole at 100 mg/L and nitrapyrin at 100 mg/L were apparently fatal to ammonium-oxidizing bacteria. In laboratory experiments with soil amended with nitrapyrin or etridiazole, both inhibitors were more bactericidal than in aqueous culture. Nitrification did not resume until 4 to 5 weeks after adding 0.5 mg inhibitor/kg soil and, especially with etridiazole, the population of ammonium oxidizers was drastically diminished and did not fully recover. However, in field experiments, nitrapyrin and etridiazole injected at 1.5 kg/ha with aqueous urea did not affect numbers of ammonium-oxidizing bacteria in cross-sections of the injected band of soil taken after injection in autumn or spring, although the inhibitors were present in concentrations that effectively inhibited nitrification.

ISSN:0008-4166    

DOI:10.1139/m82-163

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

When strain C3 ofKlebsiella pneumoniaeis grown on a minimal medium with excess glucose, isocitrate dehydrogenase, malate dehydrogenase, and succinate dehydrogenase specific activities increase in the last period of the exponential growth phase and in the beginning of the stationary phase. Glucose exhaustion does not alter the development of malate dehydrogenase and succinate dehydrogenase, but specific activities are higher than those obtained with excess glucose. In contrast, glucose exhaustion can be correlated with a decrease of isocitrate dehydrogenase specific activity in the stationary phase. Induction of strain C3 isocitrate dehydrogenase by glucose in complex medium and repression by cAMP in mineral medium were observed. Glucose induction and the NADP/NADPH ratio are suggested as regulatory mechanisms controlling isocitrate dehydrogenase synthesis in theEnterobacteriaceae, but the former appears to be restricted to someKlebsiellastrains.

ISSN:0008-4166    

DOI:10.1139/m82-164

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The cells ofZymomonas mobilisvar.mobiliscontained 6.3% of the chloroform–methanol–water extractable lipids (dry weight basis) and 1.5% of bound lipids. The extractable lipids were 96.8% polar lipids and 3.2% neutral lipids. The neutral lipids contained squalene, and 21 pentacyclic triterpene hydrocarbons comprised 1.4% of the total lipids. The remaining neutral lipids consisted of relatively small quantities of components tentatively identified as free fatty acids, tri-, di-, and mono-glycerides, lipoamino compounds, and pigments. The polar lipids consisted of methanol-soluble and -insoluble fractions. The methanol-soluble fraction consisted of phosphatidylethanolamine as the principal lipid and lysophosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, dimethylphosphatidylethanolamine, and phosphatide acid as the minor lipids. The methanol-insoluble fraction consisted of glycolipoproteins comprising glucosamine, galactosamine, myristic acid, and amino acids. This glycolipoprotein fraction differed from the material isolated by standard procedures for extracting lipopolysaccharides. The lipopolysaccharide fraction, in turn, was distinctly different from the lipopolysaccharides of other Gram-negative species, since deoxyhexoses, pentoses, hexoses, aminopentose, uronic acid, phosphate, and myristic acid were the principal constitutents. There was no evidence for ketodeoxyoctulonic acid, heptoses, or hydroxy fatty acids. Hexosamines were detected in trace amounts only by colorimetric analysis.

ISSN:0008-4166    

DOI:10.1139/m82-165

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The early events in the interaction of two polyene (amphotericin B and nystatin) and five imidazole (clotrimazole, ketoconazole, miconazole, isoconazole, and econazole) antimycotics used at fungicidal concentrations with the surface ofCandida albicanswere studied by scanning electron microscopic examination of treated intact young yeast cells, treated spheroplasts, and spheroplasts liberated from treated young yeast cells. In all cases, treatment lasted 2 h. The polyenes passed through the yeast cell wall and interacted with the cytoplasmic membrane causing the spheroplasts to lose their characteristic spheric form and to liberate their contents. Clotrimazole caused the formation of numerous circular openings in the cytoplasmic membrane, but only when the agent was used to treat spheroplasts directly. Ketoconazole, miconazole, isoconazole, and econazole interacted with the cell wall causing formation of convolutions and wrinkles. The three imidazole derivatives that are structurally closely related, miconazole, isoconazole, and econazole, inhibited the enzyme-catalyzed release of spheroplasts from young yeast cells.

ISSN:0008-4166    

DOI:10.1139/m82-166

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

When rabbits were injected with the heat-denatured alpha toxin (toxoid) ofStaphylococcus aureus, the immune response was demonstrated by an increase in antitoxin that fixed complement. Such antitoxin was detected in 72% of normal human sera. After fractionation of the antitoxin into two types (the antibinding antibodies and the indirect hemagglutinating antibodies), both types of antibodies were found to fix complement in the standard serological complement fixation test. In addition, the indirect hemagglutinating antibodies were capable of fixing complement when the antigen (alpha toxin or toxoid) was covalently or noncovalently bound to erythrocyte membranes. The fixation of complement by membrane-bound immune complexes did not result in lysis of the carrier erythrocytes. The prevalence of complement-fixing antitoxin in normal humans and animals raised the concern that the outcome ofin vivoexperiments involving alpha toxin could be influenced by the immune status of the host.

ISSN:0008-4166    

DOI:10.1139/m82-167

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Using the OsO4isolation method, more than 200Frankiastrains were obtained from 27 provenances of the two alder species represented in Quebec, i.e.,Alnus crispa(Ait.) Pursh. andAlnus rugosa(Du Roi) Spreng. TheFrankiaisolates were evaluated for morphological characteristics, infectivity, and efficiency. Variations in these factors were noted between provenances and also between isolates from a single provenance. The distribution of sporulating (Sp+) and nonsporulating (Sp−) type isolates was found to be related to host plants and provenance. The sporulating or nonsporulating endophytic character was found to significantly affect efficiency. This endophytic character was recognized as one of the valid criteria that should be used in the awaited species definition in the genusFrankia.

ISSN:0008-4166    

DOI:10.1139/m82-168

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Submerged cultures of wild-typePolysphondylium pallidum(WS320) undergo a developmental sequence in which cells agglutinate and form tight aggregates within which extensive stalk and some spore differentiation occurs. Development of submerged cultures ofP.pallidumbears many similarities to fruiting body cultures except that differentiation occurs in the absence of morphogenesis. Here we extend the results of an earlier study of submerged cultures ofP.pallidumWS320 (Paterno and O'Day. 1981. Can. J. Microbiol. 27: 924–936) by showing that these cultures respond to several exogenous agents (cyclic AMP, lithium chloride, ammonium chloride, colchicine, and concanavalin A) in the same way as slime mould fruiting body cultures. However, two mutants abnormal in cyclic AMP production which complement to form fruiting bodies on agar plates could not form normal submerged culture aggregates when mixed together. Complementation tests with mutant and wild-type cells also failed. The inability of the mutants (PN507 and PN518) to complement in submerged cultures suggests that their fruiting complementarity may be based on a morphogenetic event. A low molecular weight fraction from wild-type cells could enhance development and stalk cell differentiation in WS320 and one mutant, PN507, but not in PN518. Together these data reveal that submerged cultures can be utilized to test the effects of extracellular factors on development and used as a source for the isolation of factors that regulate cellular differentiation.

ISSN:0008-4166    

DOI:10.1139/m82-169

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Gel electrophoresis of DNA from 70 clinical strains ofSalmonellarevealed a heterogeneous plasmid population. Plasmid DNA, ranging in molecular weight from 1.4 × 106to 145 × 106, was demonstrated in 26 of 32 antibiotic-resistant strains. Several resistant strains carried up to six plasmids; however, of these, five strains which were multiply resistant contained a single plasmid of molecular weight 54 × 106to 145 × 106. Only one incompatibility group H2 (IncH2) plasmid (pDT28) was detected in a strain ofS.heidelberg; thus, this represents a reduction in the prevalence of these plasmids in OntarioSalmonellastrains since 1974. The pDT28 plasmid resembled other IncH2 plasmids by its high molecular weight (145 × 106) and by virtue of its temperature-sensitive mode of transfer, resistance to tellurium, and inhibition of coliphage development. Of the 38 antibiotic-susceptibleSalmonellastrains, approximately half contained plasmids, ranging in molecular weight from 1.4 × 106to 60 × 106. The plasmid-containing antibiotic-susceptible strains carried either a group of two to four small plasmids, with molecular weights less than 4.5 × 106, or a single large plasmid of molecular weight 23 × 106or 60 × 106.

ISSN:0008-4166    

DOI:10.1139/m82-170

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

The cellulose-solubilizing and carboxymethylcellulase activities ofAcetivibrio cellulolyticuswere observed to exist largely in a soluble form whereas β-glucosidase activity was cell associated. Reducing agents significantly enhanced cellulose-solubilizing activity, and thiol-binding agents at micromolar concentrations resulted in almost total inhibition of this activity. Carboxymethylcellulase activity was also inhibited by these agents but to a lesser degree. Cellulose-solubilizing activity was strongly stimulated by Mg2+and Ca2+but these ions had a negligible effect on carboxymethylcellulase activity. Cellulase activity was not inhibited by glucose and only slightly by cellobiose. A strong preference forp-nitrophenylglucoside over cellobiose by β-glucosidase activity was observed.

ISSN:0008-4166    

DOI:10.1139/m82-171

出版商:NRC Research Press    

年代:1982

数据来源: NRC

摘要:

Approximately 30 purine compounds were examined for their influence on the energy-linked amino acid transport systems ofAchlya(a freshwater mold). Most of them were inhibitory, and their effectiveness was related to (a) the presence of a substituent group at position 6 of the purine ring, (b) the length of hydrocarbon chain as substituent, and (c) the type of linkage between the substituent group and the heterocyclic ring. The most effective linkage group was SH followed by an NH2group, and an oxygen bridge which was the least effective. Inhibition was immediate (suggesting an interaction with the cell membrane) and pH and temperature dependent. Only tryptophan uptake was anomalous, for while its transport was inhibited, its binding to a cell wall – membrane proteoglycan was stimulated severalfold. From kinetic studies, we deduced that the analogues and tryptophan were interacting with the same cell entity. Nucleoside forms of the analogues did not inhibit amino acid transport; this was understandable, since nucleosides are transported by an energy-linked system whereas nucleic acid bases are not. The purine analogues themselves were taken up very poorly by this organism.

ISSN:0008-4166    

DOI:10.1139/m82-172

出版商:NRC Research Press    

年代:1982

数据来源: NRC