ISSN:0008-4166    

DOI:10.1139/m94-069

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Thirteen isolates ofLegionella pneumophilaserogroup 1 (five from patients, eight from water) were screened for their virulence in guinea pigs after intraperitoneal injection and for their infectivity in L929 mouse cells. Since these isolates included three monoclonal antibody subtypes and four genotypes, the relative influence of these parameters on the pathogenicity of naturally occurringL.pneumophilacould be assessed. There was no correlation between infectivity in the L929 assay and virulence for guinea pigs. The source of the isolate, patient or environmental, as well as the isolate's monoclonal antibody subtype did not correlate with virulence. At thep < 0.05 level, isolates with genotype IIb (20-MDa plasmid andEcoRI fragmentation patternb) were significantly more virulent (mean log LD506.84) than genotype VIb (100-MDa plasmid, patternb), IIId (72- and 96-MDa plasmids, patternd) or Oc (no detectable plasmid, patternc) isolates. Genotype IIId isolates were the least virulent (mean log LD509.49). Plasmid-containing isolates were more infective than plasmidless ones in L929 cells (p = 0.0001). We conclude that our strain types ofL.pneumophilaexhibit a gradation in virulence for guinea pigs and that infectivity in L929 cells does not correlate with virulence for guinea pigs.Key words:Legionella, virulence, genotype, plasmids.

ISSN:0008-4166    

DOI:10.1139/m94-070

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Two species of bacteria, identified asPseudomonas stutzeri(P-16) andPseudomonas saccharophila(P-15) by fatty acid methyl ester analysis, were found in a phenanthrene enrichment culture of a creosote-contaminated soil. The organisms are shown to be physiologically dissimilar, and their genetic relatedness is discussed. Phenanthrene degradation by both organisms followed Michaelis–Menten kinetics, allowing for the determination of half-saturation (Ks) and maximum activity coefficients, using nonlinear regression. Both organisms utilized kinetically similar enzymes for phenanthrene uptake and oxidation, as evidenced by similarKscoefficients of approximately 0.2 mg/L and temperature optima of 40 °C, but levels of expression differed with different media. Each organism degraded phenanthrene via salicylic acid, but patterns of intermediate metabolism were shown to differ. P-15 excreted 1-hydroxy-2-naphthoic acid during growth on phenanthrene and demonstrated Michaelis–Menten kinetics for the oxidation of 1-hydroxy-2-naphthoic acid by resting cells. P-16 excreted only trace amounts of 1-hydroxy-2-naphthoic acid and demonstrated linear kinetics in response to 1-hydroxy-2-naphthoic acid concentration. P-15 was found to form thick biofilms on phenanthrene crystals and was characterized by a hydrophobic cell surface, whereas P-16 grew mostly in suspension and was hydrophilic. Neither organism produced significant amounts of biosurfactants when grown on phenanthrene. The implications of these findings for the design of systems to remediate contaminated soil are discussed.Key words: phenanthrene, 1-hydroxy-2-naphthoic acid, biodegradation, kinetics, polycyclic aromatic hydrocarbons.

ISSN:0008-4166    

DOI:10.1139/m94-071

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The fluorescent probe fura-2 was used to measure the intracellular free calcium concentration [Ca2+]iin the Gram-positive skin bacteriumPropionibacterium acnes. Three methods for loading the probe intoP.acneswere used. Two consisted of using the membrane permeable acetoxymethyl ester of fura-2, fura-2/AM, whereas in the third method, fura-2 was loaded directly into the bacteria by means of an acid shock procedure. One method using fura-2/AM was found to be satisfactory. In this case, a statistical experimental designwas used to devise a suitable loading procedure. [Ca2+]iofP.acneswas dependent upon the external calcium concentration. At low external concentrations (0.2 < [Ca2+]o < 5 μM), [Ca2+]iwas 135 ± 13 nM (n = 20). An increase in [Ca2+]oto 1 mM resulted in an increase in [Ca2+]ito approximately 280 ± 40 nM whereas in a Ca-free solution ([Ca2+]o < 5 nM), [Ca2+]idecreased to a lower resting value of 70 ± 7 nM. The time constants for calcium regulation upon step changes in the external concentration were of the order of 10 min. Intracellular alkalinization induced by changes in the external pH (pHo) resulted in an increase in [Ca2+]iwhen [Ca2+]owas in the range 0.2–5 μM. [Ca2+]iwas approximately constant in the range pHo5.5–7.7 but increased when pHo > 8.0. This increase was partially reversed when pHowas again lowered to below 8.0. In a Ca-free solution, little or no increase in [Ca2+]iwas observed when pHo > 8.0.Key words:Propionibacterium acnes, fura-2, calcium.

ISSN:0008-4166    

DOI:10.1139/m94-072

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Eighty regional strains ofVibrioisolated from the seasonally cold waters of coastal Newfoundland, and a number ofVibrioreference cultures, were studied. The regional strains had been isolated from the brown macroalgaAlaria esculentaand the giant scallopPlacopecten magellanicusand were known to grow at 4 °C. The strains were grouped according to their arginine-dihydrolase reactions and examined by numerical analysis. According to phenotypic properties the arginine-dihydrolase positive strains closely resembledVibrio splendidusbiovar I. Most clusters of the arginine-dihydrolase negative strains appeared to be unique but the closest phenotypic resemblance among some strains was withVibrio ordalii. Some strains were examined using the random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) technique for fingerprinting and it was shown that the regional strains were significantly different from eitherV.splendidusbiovar I orV.ordalii. Generally, the strains from seaweed clustered separately from those that were from scallops. Strains in some clusters, especially those from the seaweed, were able to utilize most of the compounds that were tested as sole sources of carbon and energy.Key words: numerical taxonomy, marine bacteria,Vibrio, psychrotrophs, RAPD-PCR.

ISSN:0008-4166    

DOI:10.1139/m94-073

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Competition from existing soil rhizobia has limited the benefits from nitrogen fixation for soybean grown in the American Midwest. A strategy being considered to overcome this problem is the use of varieties that are restricted in nodulation with soil strains, but nodulate normally with inoculant bradyrhizobia. In this study we examine the efficiency in nodulation of strains ofBradyrhizobium japonicumthat have been reported as restricted in nodulation with specific genotypes of soybean, using a root-tip marking procedure in growth pouches. WhenB.japonicumUSDA110 was applied to the soybean cultivars Hardee and Fiskeby V at the rate of 3.50 × 104 cells/pouch, more than 75% of the plants were nodulated above the root-tip mark, and average uppermost nodule position was above the root-tip mark. By contrast, when this strain was applied in similar concentration to the soybean cultivar Peking, few plants developed nodules above the root-tip mark, and the average position of the uppermost taproot nodule was nearly 30 mm below this mark. Nodulation was improved at higher rates of inoculation, but even when 3.50 × 106 cells were applied to each pouch, less than 50% of the plants were nodulated above the root-tip mark.Bradyrhizobium japonicumstrain CB1809 (=USDA136) was also efficient in nodulation with cv. Fiskeby V, but with cv. Hardee, less than 65% of plants were nodulated above the root-tip mark, irrespective of inoculation rate. Because restriction of nodulation with the strains initially tested was not absolute, we examined the patterns of nodulation obtained following the inoculation of two restriction hosts, Peking and PI371607. In pure culture, serogroup USDA110 strains failed to induce significant taproot nodulation of cv. Peking in Leonard jars, but did induce lateral root nodulation. However, in a glasshouse experiment contrasting soil- and seed-applied inoculant, lateral-root nodulation of the restriction host PI371607 by USDA123 was not significant.Key words:Glycine max, competition, restriction, nodulation.

ISSN:0008-4166    

DOI:10.1139/m94-074

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A mutant of the fungusAphanocladium album, characterized as chitinase-overproducing, does not grow on medium containingN-acetyl-D-glucosamine as sole carbon source. The lack of growth may indicate a defect either in the uptake system or in any subsequent step in the metabolism ofN-acetyl-D-glucosamine. Since transport is the first step at which control of metabolism could operate, the mutant strain was studied for its ability to transportN-acetyl-D-glucosamine. The results were compared with those obtained with the wild-type strain. Labelling experiments, designed to characterizeN-acetyl-D-glucosamine uptake, indicated that uptake was due to the simultaneous operation of two transport systems, one of high affinity and one of low affinity. Wild-type and mutant strains displayed differentKmvalues for the low-affinity system. TheKmvalue of the mutant's low-affinity system was very high compared with that of the wild-type strain.Key words: deuteromycete, filamentous fungus,Aphanocladium album, uptake,N-acetyl-D-glucosamine.

ISSN:0008-4166    

DOI:10.1139/m94-075

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Organic acids, similar in structure to naphthenic acids, have been associated with the acute toxicity of tailings produced by the oil sands industry in northeastern Alberta, Canada. Bacterial cultures enriched from oil sands tailings were found to utilize as their sole carbon source both a commercial mixture of naphthenic acids and a mixture of organic acids extracted from oil sands tailings. Gas chromatographic analysis of both the commercial naphthenic acids and the extracted organic acids revealed an unresolved "hump" formed by the presence of many overlapping peaks. Microbial activity directed against the commercial mixture of naphthenic acids converted approximately 50% of organic carbon into CO2and resulted in a reduction in many of the gas chromatographic peaks associated with this mixture. Acute toxicity testing utilizing the Microtox test revealed a complete absence of detectable toxicity following the biodegradation of the naphthenic acids. Microbial activity mineralized approximately 20% of the organic carbon present in the extracted organic acids mixture, although there was no indication of a reduction in any gas chromatographic peaks with biodegradation. Microbial attack on the organic acids mixture reduced acute toxicity to approximately one half of the original level. Respirometric measurements of microbial activity within microcosms containing oil sands tailings were used to provide further evidence that the indigenous microbial community could biodegrade naphthenic acids and components within the extracted organic acids mixture.Key words: naphthenic acids, biodegradation, oil sands tailings, toxicity testing.

ISSN:0008-4166    

DOI:10.1139/m94-076

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Possible mechanisms involved in the suppression of the take-all fungus (Gaeumannomyces graminisvar.tritici) by a sterile red fungus were examined. Studies on the effects of foliar application of thiamine to plants showed a reduction in take-all suppression by the sterile red fungus thereby indicating that competition for this particular vitamin, required by both fungi, could be one of the mechanisms of antagonism. Treatment with the exudate produced by the sterile red fungus on solid substrates resulted in lysis of the hyphae of the take-all fungus. Exudate produced on sterilised wheat seeds was more inhibitory to the take-all fungus than that produced on ryegrass seeds. Fungal inhibition increased as the duration of exposure to the exudate increased. The primary effects of hyphal interactions between the sterile red fungus and the take-all fungus were evident as coiling and contact lysis. It is possible that a combination of mechanisms including the above may be involved in suppression of the take-all fungus by the sterile red fungus.Key words: take-all suppression, sterile red fungus.

ISSN:0008-4166    

DOI:10.1139/m94-077

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Two extracellular β-xylosidases, xylosidase I and II, were isolated from the ruminal fungusNeocallimastix patriciarum27 after growth in a barley straw medium. Xylosidase I was purified 88-fold to apparent homogeneity by ion-exchange, affinity, and gel filtration chromatography. The purified xylosidase I had an isoelectric point (pI) of 4.7 and was a monomelic protein with a molecular mass of 39.5 kDa as estimated by both SDS-PAGE and gel filtration. Xylosidase II was partially purified to approximately 95% purity. Xylosidase II had the same pI (4.7) as xylosidase I, and appeared to be a dimeric enzyme composed of two polypeptides with molecular masses of 85 and 45 kDa, respectively, on SDS-PAGE. Peptide mapping of the three proteins suggested that xylosidase I was a truncated product originating from xylosidase II. Xylosidases I and II had similar pH optima of 6.0, but different temperature optima of 50 and 40 °C, respectively. TheKmandVmaxfor xylosidase I were 0.59 mM ofp-nitrophenyl-β-D-xylopyranoside and 38.04 U∙mg protein−1, respectively, and those for xylosidase II were 0.13 mM and 8.9 U∙mg protein−1, respectively. Both enzymes hydrolysed pNPX and xylobiose with the production of xylose, but only xylosidase I exhibited activity towardp-nitrophenyl-α-L-arabinofuranoside.Key words: xylosidase,Neocallimastix,patriciarum, glycosid

ISSN:0008-4166    

DOI:10.1139/m94-078

出版商:NRC Research Press    

年代:1994

数据来源: NRC