摘要:

Erythrocytes of different animal species have variable hemolytic sensitivity to staphylococcal alpha toxin. Specific and non-specific binding of toxin was measured using fluorescein-labelled toxoid. These studies indicate that toxoid binding to erythrocytes increases with concentration for all species tested. Scatchard plot analyses of 35 animals representing seven species indicate that rabbit, pig, cow, and chicken erythrocytes possess 125 980, 103 920, 82 500, and 41 200 receptors per cell, respectively. The number of receptors remains constant over a period of at least 10 days. No detectable receptors were found for human, rat, and guinea pig erythrocytes. A correlation coefficient of 0.992 exists between receptor number and hemolytic sensitivity for those species having receptors. Variation in hemolytic sensitivity is governed by receptor number and not by variation in the dissociation constant. A threshold sensitivity of 37 000 receptors per cell has been calculated. Since species lacking detectable receptors have considerable sensitivity to hemolysis, it is proposed that two binding mechanisms, specific and non-specific, exist which prepare erythrocytes for destruction.

ISSN:0008-4166    

DOI:10.1139/m79-192

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Two strains ofBacillus sphaericus, SSII-1 and 1593, were bioassayed for toxic activity against second-instar larvae of the mosquitoCulex pipiens quinquefasciatus. It was found that strain 1593 developed a level of toxicity 3000 times that of strain SSII-1. Although the toxic activity ofB.sphaericusSSII-1 was relatively unchanged throughout growth, an increase in activity of strain 1593 occurred as the bacteria began to sporulate. Strain differences were examined by (i) growth cycle experiments, (ii) bioassays of the toxicity of oligosporogenous mutants, and (iii) manganese limitation experiments. The toxin of strain 1593 was shown to be more stable than that of strain SSII-1. Unlike the spores of strain SSII-1, the spores ofB.sphaericus1593 were found to be highly toxic. Thin sections of SSII-1 or 1593 cells did not reveal the presence of any inclusion body that might be related to toxicity.

ISSN:0008-4166    

DOI:10.1139/m79-193

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A broth-disc technique has been developed to demonstrate the antibiotic synergism of some broad-spectrum penicillins plus an aminoglycoside againstPseudomonas aeruginosaand enterococci. Utilizing the zone sizes obtained from Kirby–Bauer susceptibility tests, approximate minimum inhibitory concentrations of each antibiotic upon individual isolates were derived using standard regression curves. One-fourth of each value was calculated and the approximate desired concentration then prepared in Mueller–Hinton broth through use of the labelled antibiotic disc content. Tubes were inoculated with a standardized suspension of organism and incubated at 35 °C for 18–24 h. Subsequently, inhibitory end points were recorded.This approach to synergy testing showed good correlation with the standard checkerboard method. The broth-disc synergistic assay is also reproducible, financially feasible, and less time-consuming to execute.

ISSN:0008-4166    

DOI:10.1139/m79-194

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Lipid content and composition were determined inAzotobacter chroococcumgrown, under nitrogen-fixing conditions, in continuous culture with intense aeration under atmospheres containing between 5 and 40% O2. Total lipid content remained almost constant at approximately 9% of dry weight.Phospholipid content was maximal at 20% O2where it accounted for 92% of total lipid, and was minimal at 40% O2. Phosphatidylethanolamine was the only species of phosphatide detected in this fraction. Neutral lipid content was minimal at 20% O2and maximal at 40% O2where it represented approximately 30% of the total lipid. Glycolipid remained between 2 and 13% of total lipid throughout. The principal fatty acids ofA.chroococcumwere hexadecanoic (C16:0), hexadecenoic (C16:1), and octadecenoic acid (C18:1) at all O2tensions, but C18:1increased at the expense of C16:1at higher O2tensions, particularly in free fatty acid and phospholipid fractions. [U-14C]acetate was readily incorporated into lipid at both 20 and 40% O2but total incorporation was much greater at 20% O2.

ISSN:0008-4166    

DOI:10.1139/m79-195

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Lysosomal enzyme release from cells involved in inflammatory response could play a central role in the pathogenesis of endotoxin shock. Therefore we have studied the release of the lysosomal enzyme, β-glucuronidase, from peritoneal macrophages obtained from normal and endotoxin-tolerant B6CBF1 mice both before and after challenge with lethal doses of endotoxin. Unstimulated cells from tolerant mice spontaneously released a smaller percentage of their total β-glucuronidase content in culture than cells from normal mice during a 5-h incubation period. In support of the lysosomal enzyme release hypothesis, it was found that the invitrorelease of β-glucuronidase was accelerated when cells were collected from the mouse peritoneum 3 h after i.v. challenge with a lethal dose (1.0 mg) of endotoxin. The increasedin vitro"leakiness" of peritoneal macrophages following endotoxin challenge was less marked when tolerance was induced in mice by prior repeated injections of endotoxin. Furthermore, measurements of the total enzyme activities of peritoneal cells revealed a significant reduction in the β-glucuronidase content of cells from normal mice 3 h after endotoxin challenge but no such decrease for cells from tolerant mice. These results suggest that macrophages in endotoxin-sensitive mice release their lysosomal enzymesin vivoduring endotoxemia, whereas cells found in tolerant mice do not.In related experiments, the phagocytosis of latex particles and inhibition of bacterial growth by macrophages from normal and tolerant mice were compared. These studies suggest that cells from tolerant mice may also release a smaller percentage of their lysosomal enzymes during phagocytosis.

ISSN:0008-4166    

DOI:10.1139/m79-196

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Mixtures of anionic HgCl3−/HgCl42−comhplexes were less toxic to terrestrial bacteria (Erwinia herbicola,Agrobacterium tumefaciens), to marine bacteria (Acinetobactersp.,Aeromonassp.), and to bacteriophages (11M15 ofStaphylococcus aureusand P1 ofEscherichia coli) than were equivalent concentrations of Hg as cationic Hg2+. The toxicity of 1 ppm Hg toA.tumefaciens,Aeromonassp., and (11M15 was less in seawater than in lake water. Inasmuch as the Hg–Cl species are formed in environments of high chloride concentration, it was postulated that the lower toxicity of Hg in seawater was a result of the formation of HgCl3−/HgCl42−complexes.

ISSN:0008-4166    

DOI:10.1139/m79-197

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Liquid poultry manure was applied to three forest sites at 35, 70, and 225 metric tonnes (1 tonne = 1000 kg) per hectare (1 ha = 10 000 m2) for 1 to 3 years. Two of the sites were white pine plantations, one dry, one moist, and the third site was mixed hardwoods. Over a period of 35 months the total bacterial population in litter and in soil, in both control and manure plots, was studied as well as the ability of the population to produce extracellular proteases, cellulases, lipases, pectinases, and amylases. Total bacterial counts in litter tended to be higher in the autumn and lower in the spring. Litter always contained about 10-fold more bacteria than soil and the number of bacteria in soil fluctuated little with season or treatment. In white pine litter, bacteria able to excrete protease were more numerous than other enzyme-producing bacteria. More bacteria able to excrete lipases were found on moist than on dry sites, especially on manured plots. At the end of the 35-month test period, all bacterial counts in manured plots had returned nearly to the original level of the control. Statistical analysis revealed significant differences in total bacterial count and counts of specific enzyme producers between manured and control plots. Little difference was seen among rates of manure application. Adding large amounts of poultry manure to these forest plots did not greatly change the bacterial ecology of the soil or litter.

ISSN:0008-4166    

DOI:10.1139/m79-198

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The percentage of low-level streptomycin-resistant (20 μg/mL) bacteria in surface-sterilized or washed maize roots was more than a thousand times higher than that in soil populations. There was also a higher incidence of resistant bacteria in rhizosphere as compared with non-rhizosphere soil and bacteria isolated from maize roots were relatively tolerant to several other antibiotics.Azospirillum lipoferumwas predominant in surface-sterilized roots of field-grown maize and was low-level streptomycin-resistant while most soil isolates were sensitive. Inoculation withA.brasilenseisolated from wheat roots was unsuccessful in terms of establishment even when streptomycin-resistant strains were used. Unidentified causes of specific plant–bacteria affinities therefore transcend the role of antibiotic resistance in maize root infection.

ISSN:0008-4166    

DOI:10.1139/m79-199

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Forty-two actinomycete strains were isolated by enrichment techniques from soils and other lignocellulose-containing natural habitats. Isolates were screened for their lignocellulose-decomposing abilities using a substrate weight loss –14C-labeled lignocellulose degradation assay which determined the relative abilities of each isolate to attack lignin versus glucan components of lignocellulose. SixStreptomycesstrains were selected for further study, based upon their abilities to decompose significantly both lignin and glucan components of lignocellulose. The selected strains were examined under defined cultural conditions for their abilities to decompose14C-labeled lignocelluloses prepared from Douglas fir. The14C-labeled lignocellulose substrates included specifically lignin-labeled or glucan-labeled lignocelluloses, and two [14C]lignin lignocelluloses labeled specifically in only the lignin side chain or ring components. Results showed that theStreptomycesstrains decomposed substantial amounts of both lignin and glucan components to14CO2, and14C-labeled water-soluble products. As compared with previously described lignocellulose-degrading streptomycetes, these strains were generally more efficient decomposers of the lignin component of lignocellulose, but were similar in their abilities to decompose the glucan component. Characterization of growth on specifically labeled lignins showed that aromatic ring structures within the lignin were cleaved and a substantial percentage of the ring carbons were released as CO2. In contrast, side-chain components were attacked to only a limited degree. These streptomycetes were similar to other recently characterized lignin-decomposing bacteria in their overall abilities to degrade lignin, but their specificity of attack on the structural components of lignin appears to be different.

ISSN:0008-4166    

DOI:10.1139/m79-200

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

AnArthrobacterspecies, which utilized thiocyanate (SCN−) as a nitrogen source, was isolated from soil by the enrichment culture method. The organism tolerated SCN−concentrations up to 0.1 M. On addition of nitrate or ammonium ion to cultures of the isolate growing in the presence of SCN−, the organism continued to degrade SCN−. Degradation could be followed by release of14CO2from SCN−(14C). The SCN−-degrading activity diminished to low levels as the stationary phase of growth was approached.

ISSN:0008-4166    

DOI:10.1139/m79-201

出版商:NRC Research Press    

年代:1979

数据来源: NRC