摘要:

A radioimmunodiffusion technique for detecting low levels of diphtheria antitoxin was developed. Diphtheria toxoid was labelled with125I to facilitate detection of lines of precipitation by the use of X-ray film, the lower limit of detection being 0.001 unit per millilitre of diphtheria antitoxin.

ISSN:0008-4166    

DOI:10.1139/m77-125

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

It has been shown that 2,5-dihydroxy-1,4-benzoquinones decrease vegetative growth and inhibit spore germination of 12 species of fungi belonging to six diverse genera. The nature of the substituents at the 3 and 6 positions of the quinone ring also affected their growth-inhibitory properties; generally those substituents of lower polarity inhibited growth at lower concentrations. As in the case of cochliodinol, chemical modification of the quinone group, or the hydroxyl groups of the quinone ring, in compounds of the polyporic acid series, also led to loss of biological activity.

ISSN:0008-4166    

DOI:10.1139/m77-126

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Crude chemical fractions, homogenates, and whole cells ofMycoplasma boviswere tested for serological reactivity using agar gel diffusion, ring precipitation, indirect hemagglutination, inhibition of growth inhibition (IGI), and complement-fixation (CF) tests. Only the IGI and the CF tests gave sensitive and reproducible serological information. Preliminary studies indicated lipids to be the serologically reactive components ofM.bovis.

ISSN:0008-4166    

DOI:10.1139/m77-127

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

During a study of cyclopiazonic acid (total α- and β-cyclopiazonic acids, CA) production byPenicillium cyclopiumWestling, it was found that nitrogen depletion controlled the advent of secondary metabolism and that nitrate reduction was not rate-limiting. In concert with N depletion both tryptophan (Trp) biosynthesis and glucose catabolism fell. The rate of Trp production dropped to match the rate of CA biosynthesis. Glucose utilization varied between an early and late preference for the pentose cycle, with a mixture of pentose and Emden–Meyerhof pathways at an intermediate time. This pattern may well reflect the need for erythrose-4-phosphate in Trp biosynthesis. Additions of Trp caused a drop in CA production possibly because of repression of Trp synthetase. Exogeneous dimethylallylpyrophosphate (DMAPP) increased CA biosynthesis, while mevalonic acid had no effect which suggested a rate-limiting step between these two metabolites. These changes probably best fit Bu'Lock's hypothesis that secondary metabolism links fermentative and aerobic metabolism (ATP generation). In this case protein and polyisoprenoid biosynthesis, sugar utilization, and energy requirements would all be interlocked with the advent of secondary metabolism. The possible relationship between the observed metabolic changes and energy control were supported by electron-microscopic examination of the mitochondriain situ, when these ATP-generating organelles underwent major changes. Addition of ATP to the culture depressed CA production, as did excessive aeration. The metabolic regulator cAMP had no effect other than to increase autocatalysis.

ISSN:0008-4166    

DOI:10.1139/m77-128

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Ineffective nodules, formed on Clark-63 soybeans byRhizobium japonicumstrain 8-0 (Iowa), and effective nodules, formed on Clark-63 soybeans by strain 138 (U.S.D.A.), have been examined by electron microscopy at 10–12, 16, and 21 days after seed inoculation. Though strain 8-0 bacteria are able to infect the host cells in a normal manner, infection is followed closely by a progressive deterioration of the symbiosis involving selective autolysis of host cell contents and degeneration of the intracellular bacteria. The host cells, though disrupted, apparently survive the destruction of the bacteria. The observed ultrastructural changes suggest either a suddenly manifested incompatibility between host and rhizobia, or an acute, localized, nitrogen starvation in the infected cells.

ISSN:0008-4166    

DOI:10.1139/m77-129

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Four methods were compared in an international comparative study for the enumeration ofClostridium perfringens: the SFP (Shahidi-Ferguson perfringens) agar (A), TSC (tryptose–sulfite–cycloserine) agar (B), SC (sulfite–cycloserine) agar (C), and neomycin blood agar (D) methods. The confirmedC.perfringenscounts were slightly lower for D than for A–C. The percentages of presumptive colonies confirmed asC.perfringenswere essentially the same in each method. The relative numbers of nonspecific colonies were the lowest in C, followed by B, D, and A. The methods were also compared for simplicity and for aspects associated with the recognition and selection of presumptive colonies.

ISSN:0008-4166    

DOI:10.1139/m77-130

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

The effect of up to 263.7 mMsodium chloride on the growth and methane production by pure cultures ofMethanospirillum hungatiiGP1,MethanobacteriumMOH,Methanobacterium thermoautotrophicum, and an unidentified methanogen was studied. Growth and methane production byM.hungatiiGP1 were not affected up to 97.3 mMNaCl but there was some inhibition of growth at higher concentrations. Growth ofMethanobacteriumMOH was independent of sodium chloride concentration within the range investigated. For the unidentified methanogen, optimum growth and methane production occurred at 15.2 mMNaCl, while growth ofM.thermoautotrophicumwas not affected by sodium chloride concentrations up to 15.2 mM. Concentrations over 15.2 mMwere inhibitory to these two organisms. The 15 mMsodium chloride concentration used by some investigators appears suitable for isolation and cultivation of methanogens since all the organisms tested in this study exhibited good growth and methane production at this salt concentration.

ISSN:0008-4166    

DOI:10.1139/m77-131

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Studies with a methanogenic culture enriched for use of acetic acid showed that this culture had an optimum growth temperature of 35 °C, with only small differences for other temperatures between 30 and 40 °C. The optimum temperature was the same when determined on the basis of biomass production rate during the exponential (log) phase of growth (0.08–0.09 day−1, at 35 °C), amount of biomass present at the end of the log phase (100 mg/ℓ), activity of the biomass (rate of conversion in millimoles per day per milligram (dry wt.) biomass present, 0.08 at end of log phase), or biomass yield (mg (dry wt.) biomass produced per millimole acetic acid converted, 1.0–1.1). Temperatures outside the range 30 to 40 °C caused marked reductions in the above parameters. The maximum temperature for growth was 42–44 °C; the minimum, below 15 °C, the lowest temperature studied. Acetic acid conversion to methane was 0.8–1.0 mol/mol, and was independent of temperatur

ISSN:0008-4166    

DOI:10.1139/m77-132

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Growing cultures of several strains ofPseudomonas fluorescensandPseudomonas chlororaphisproduced N2O as the only detectable gaseous product of denitrification, and other strains produced N2as the gaseous end product of denitrification. All of the nitrogen in NO3−or NO2−added to cell suspensions of the N2O-producing strainsP.fluorescensPJ 185 andP.chlororaphisB-560 was recovered as N2O. All of the nitrogen in NO3−or NO2−added to cell suspensions of the N2-producing strainP.fluorescenPJ 70 was converted to N2. Cell extracts ofP.fluorescensPJ 70, PJ 185, andP.chlororaphisB-560 exhibited NO3−reductase activity when sodium succinate was the electron donor. Reduced nicotinamide adenine dinucleotide and flavine adenine dinucleotide were required to demonstrate NO2−reductase activity in cell extracts.

ISSN:0008-4166    

DOI:10.1139/m77-133

出版商:NRC Research Press    

年代:1977

数据来源: NRC

摘要:

Fluorescein isothiocyanate-conjugated antibody to purified enterotoxin ofClostridium perfringenswas used to study the intracellular formation of enterotoxin by this organism. Enterotoxin was detected at 4 h of growth at the end of the cell containing forespore. With the development of the spore, enterotoxin accumulation continued and involved the entire length of the cell until its lysis with the release of enterotoxin and mature spore. The spores did not contain demonstrable enterotoxin. Only a certain number of the sporulated cells of the enterotoxigenic strains studied produced this toxin. The amount of enterotoxin produced varied with sporulation percentage, and between strains and individual cells.

ISSN:0008-4166    

DOI:10.1139/m77-134

出版商:NRC Research Press    

年代:1977

数据来源: NRC