摘要:

The acetylene-reduction assay was used forin situand laboratory assessment of biological nitrogen fixation in the acidic, waterlogged, muskeg ecosystem of the southern James Bay area, in the region of Moosonee, Ontario.In situassays and subsequent laboratory experimentation revealed that nitrogenase activity was predominately a function of the activities of heterocystic blue-green bacteria associated with surface water, with the phyllosphere of mosses, and with at least one lichen, a species ofPeltigera. No suchin situactivity was detected in the subsurface organic material, even when such material was amended with glucose. However, under laboratory conditions at 20 °C, nitrogenase activity was evident in the subsurface layers after an extended lag and was shown to be higher under anaerobic than under aerobic conditions, to have an optimum temperature range extending about a mean of 20 °C, and to be stimulated by glucose. This potential for subsurface nitrogen fixation proved to be related to the presence of microorganisms existing in anaerobic microsites within the organic layers and no microorganisms capable of fixation could be detected under aerobic incubation.

ISSN:0008-4166    

DOI:10.1139/m76-130

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Several strains of mycobacteria grown as surface pellicle on liquid Sauton's medium under semianaerobic conditions dissociated into three phenotypes: phenotypes 1, 2, and 3. Only phenotype 1 could be obtained in a pure state. None of these phenotypes was found to be stable: they convert from one into another and all revert to the parental strain when replaced in their usual aerobic cultural conditions. Comparative studies of phenotypes 1 and 3 have shown that significant differences exist in their physiological behaviour and antigenic composition.

ISSN:0008-4166    

DOI:10.1139/m76-131

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Chitin synthase (EC 2.4.1.16) has been characterized inAspergillus flavus. AKmvalue of 2.5 mMwas obtained for the substrate UDPGlcNAc. The enzyme had a requirement for GlcNAc, and Mg2+and activity was increased in the presence of soluble chitodextrins F1and F2. The optimum activity was obtained using Tris–HCl buffer, pH 7.5, with a secondary peak at pH 6.2 and an incubation temperature of 29.5 °C.Distribution patterns of chitin synthase in protoplasts and mycelial material were very similar. The highest specific activity was found in a 200 000 × gfraction.Enzyme levels in growing mycelium increased during the exponential growth phase after which they declined. Activity also increased during the early stages of regeneration of both conidial and mycelial protoplasts, despite an initial lack in net protein synthesis. Chitin synthase levels were also dependent upon the carbon source available during regeneration.

ISSN:0008-4166    

DOI:10.1139/m76-132

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The amino acidL-leucine serves as a good auxiliary nitrogen source forEscherichia coliK12, and in so doing is converted to alpha-ketoisocaproic acid which is excreted into the medium.L-Leucine does not serve as sole nitrogen source. Cells incubated withL-leucine as sole nitrogen source do not grow, although they do metabolize leucine, and accumulate ketoisocaproic acid in the medium.Where glycine is the only other nitrogen source, the presence ofL-leucine greatly increases the growth rate even at concentrations so low that its contribution as nitrogen donor is unlikely to be important.

ISSN:0008-4166    

DOI:10.1139/m76-133

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Cell walls of the fungusHelminthosporium spiciferum, prepared by mechanical grinding of the cells, were treated chemically and with helicase. The purified cell walls and the fractions were analyzed chemically and micromorphologically to localize the major cell-wall constituents and to determine the protective role of the pigments against degradative processes. The encrusting of the external area by the pigments associated with chitin formation leads to an increased resistance of this cell-wall area against the degradative processes.

ISSN:0008-4166    

DOI:10.1139/m76-134

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Antigenic analysis ofChlamydia psittaci,C.trachomatis, andLymphogranuloma venereum(LGV) revealed basic physicochemical differences among the three chlamydial strains. These were manifested in structural, isoelectric points, absorption spectra, and in the characteristics of the chromophobe-containing proteins. The effective period of sonication forC.psittaciandC.trachomatisis around 60 min during which the linkages most susceptible to external sonication forces were broken, releasing all attainable cellular components. Denaturation studies demonstrated that less than 50% of protein content ofC.psittaciwas denatured after 1 h of sonication, only 5% in the case ofC.trachomatis. The protein and carbohydrate content of the most reactive fractions in macrophage-spreading inhibition test were different for LGV andC.trachomatis. The structural differences appear to determine the antigenic properties observed among the chlamydial strains as well as the specificity and probably the mechanisms (s) of cellular immune reactivity to Chlamydiae. This in turn may explain the failure of chlamydial vaccines, prepared from stock strains, to protect immunized children against 'wild' chlamydial strains.

ISSN:0008-4166    

DOI:10.1139/m76-135

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Stock cultures ofXanthomonas campestrisNRRL B-1459 require special attention to maintenance and propagation to assure consistent production in good yields of the extracellular polysaccharide xanthan. Under customary conditions of propagative maintenance on agar slants, variant colony types develop that are smaller in size than the normal type. The rate of regression of the normal to the variant forms was diminished when theD-glucose content of the stock medium was sufficient to avoid depletion during storage and when transfer to fresh medium was reduced to 14-day intervals. Under conditions for polysaccharide production, the normal large-colony type gives crude culture liquors after 48 h of 7000 centipoise (cp) viscosity; the predominant variant form gives only 4000 cp. On the basis of 2.1% initialD-glucose, biopolymer yields for the normal and variant strains were 62 and 43%, respectively. Polysaccharide produced by the variant (small-colony type) differs adversely in solution properties from that of the parent strain (large-colony type); it differs also in its lower content of pyruvic acid andO-acetyl substituents. The molar ratios of constituent sugars (D-glucose,D-mannose, andD-glucuronic acid), however, were identical in polysaccharides with the normal and variant strains. Exclusion of colonial variants from fermentations is prerequisite to production of xanthan optimum in properties and yield.

ISSN:0008-4166    

DOI:10.1139/m76-136

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The reduction of acetylene to ethylene by stationary (non-shaking) cultures of free-living rhizobia under atmospheric oxygen levels has been demonstrated. Under these conditions the development of the activity is inhibited by 10 mMNH4Cl and about 20% of oxygen is required for maximal activity. When the stationary cultures were shaken, oxygen concentrations of 1% and higher were found to be inhibitory. Specific activities of 20 and 40 nmol of acetylene reduced h−1mg−1protein were observed.

ISSN:0008-4166    

DOI:10.1139/m76-137

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

L-forms ofClostridium perfringenswere induced in brain heart infusion broth containing 10% sucrose and 2 units of penicillin. After a few hours of growth, spheroplasts, granules, and elongated bacilli were apparent. At 24-h intervals, serial subcultures were made in the above medium which resulted in a culture composed entirely of spheroplasts (or protoplasts) and granules. Upon the withdrawal of penicillin these L-form cultures grew well and, after 100 passages, there was no reversion to the bacillary form. Sucrose could also be withdrawn from the medium. The effects of centrifugation, osmotic stabilizer, ultraviolet light, temperature, pH, and lyophilization upon stable L-forms were examined. L-forms were found to attach to the walls of culture tubes during growth and sheets of L-form growth were obtained on cover slips in Leighton tubes and on the sides of medicine bottles.

ISSN:0008-4166    

DOI:10.1139/m76-138

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Conjugation inGuilliermondella selenosporatook place via conjugation tubes from cells in different hyphae. Afterwards, a septum was formed in the channel connecting the two cells which turned into asci or formed buds which became asci. Conjugation between adjacent hyphal cells was also found. Cell contact without fusion with denticles and stalks, which occurs inG.selenospora, was compared with conjugation.

ISSN:0008-4166    

DOI:10.1139/m76-139

出版商:NRC Research Press    

年代:1976

数据来源: NRC