摘要:

The specific aims of this research were to evaluate the combined effects of ethanol and high-pressure homogenization at different temperatures on cell viability inSaccharomyces cerevisiaeand to study the induced modification of fatty acid composition. The decrease in viability was weak at 10°C while a homogenization pressure over 1000 bar (1 bar = 100 kPa) induced a significant reduction in viability when the cells were incubated at 20 and 30°C. The cell tolerance to pressure decreased with an increase in ethanol concentration and temperature. Ethanol, particularly intracellular ethanol accumulated byS. cerevisiae, played an important role in the response to homogenization pressure and in modification of the cell fatty acid composition. In fact, an unusually elevated accumulation of ethyl esters in lipid extracts of yeast cells subjected to high homogenization pressure, especially in the presence of exogenous ethanol and at 30°C, was observed. Moreover, only unsaturated and traces of short chain fatty acids were esterified with ethanol.Key words: Homogenization pressure, ethanol, fatty acids,Saccharomyces cerevisi

ISSN:0008-4166    

DOI:10.1139/w99-079

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

APseudomonassp. (S1) isolated from a garden soil possessed a unique nitrilase, which is capable of catalyzing the direct hydrolysis of both potassium and organic cyanides to their corresponding carboxylic acids and ammonia, without the formation of amide as an intermediate. The nitrilase was purified with 4.8% recovery in three steps from a cell extract of the strain. The relative mobility of the homogenous enzyme preparation in SDS and native polyacrylamide gels indicated molecular weight of 41 kDa, approximately.Pseudomonassp. (S1) utilized all the nitriles as carbon and nitrogen sources. The enzyme was induced by both aliphatic and aromatic nitriles, while the aliphatic olefinic nitrile - acrylonitrile was the most suitable substrate. The nitrilase also catalyzed the hydrolysis of acetonitrile, adiponitrile, benzonitrile, butyronitrile, glutaronitrile, phenylacetonitrile, succinodinitrile, and potassium cyanide, with the formation of ammonia and the corresponding carboxylic acids. The Michaelis-Menten constant, Km, of the partially purified nitrilase for acetonitrile, acrylonitrile, adiponitrile, benzonitrile, and potassium cyanide presented values of 11.26, 5.88, 10.28, 12.27, and 0.75 mM, respectively.Key words: nitriles, enzyme kinetics, nitrilase, partial purification,Pseudomonassp.

ISSN:0008-4166    

DOI:10.1139/w99-087

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Commercial enzymes and insect gut juice at various concentrations were used to digestBacillus thuringiensissubsp.sottoCry1Aa protoxin and examine the fragmentation pattern and effect on insecticidal activity. Trypsin at both high (5 mg/mL) and low (0.05 mg/mL) concentrations converted protoxin to toxin with no difference in insecticidal activity againstBombyx morilarvae. In both cases, the toxin protein had an apparentMrof 58.4 kDa (SDS-PAGE). Active toxin of identicalMrwas also produced with low concentrations of Pronase and subtilisin, but at high concentration, it was degraded into two protease-resistant fragments of apparentMr31.8 and 29.6 kDa, and exhibited no insecticidal activity. Sequencing data established the primary cleavage site to be in domain II, the receptor-binding region of the toxin, in an exposed loop between two beta-sheet strands. Fragmentation was not observed, however, when the digests were analyzed by native protein techniques, but rather the toxin molecule appeared to be intact. The amount of activated toxin produced byChoristoneura fumiferanagut juice was markedly reduced when the gut-juice concentration was increased from 1 to 50% and correlated with a loss in insecticidal activity. However, no lowerMrprotease-resistant fragments were evident in the SDS-PAGE of these digests.Key words:Bacillus thuringiensisendotoxin, Lepidoptera, proteolytic enzymes, insect gut juice, activation, digestion.

ISSN:0008-4166    

DOI:10.1139/w99-086

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The Arga River is an interesting system in which to study the impact of urban effluent pollution because it receives a single effluent in the form of wastewater discharge from the city of Pamplona. To analyze the extent of this discharge, total bacteria, culturable heterotrophic bacteria, and Gram-negative heterotrophic bacteria were enumerated and 409 isolates of the latter were identified. One sampling station was located upstream from the inflow, while five were located up to 30 km downstream. Bacterial counts increased drastically downstream from the wastewater inflow. Total bacterial numbers decreased along the 30 km downstream, the last station attaining similar values to those recorded upstream from the discharge. However, culturable heterotrophic and Gram-negative heterotrophic bacteria levels generally remained significantly higher within the 30 km zone investigated. Among the 409 isolates identified,Aeromonasspp. were the most frequent both upstream and downstream from the discharge. In contrast, although strains belonging to different genera ofEnterobacteriaceaewere found in all stations, their occurrence was significantly higher just downstream from the polluted discharge.Acinetobacterspp., which were never found upstream, were detected in all stations below the discharge. Our results clearly show that the bacterial community structure changes definitively downstream from the discharge and thatAeromonaswere common throughout the sampling zone. Thus they cannot be considered good indicators of pollution in this setting compared to some genera ofEnterobacteriaceaeor some species ofAcinetobacter,the distribution of which correlated better with the distance from the wastewater discharge.Key words:Aeromonas,Enterobacteriaceae, sewage, freshwater.

ISSN:0008-4166    

DOI:10.1139/w99-073

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A soluble cytochrome P450 (P450EP1A) induced by 2-ethoxyphenol was purified to apparent homogeneity fromCorynebacteriumsp. strain EP1. The P450EP1Ashowed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a molecular weight of about 45 kDa. The CO-reduced difference spectra of P450EP1Ahad a Soret maximum at 447.6 nm. The substrate difference spectra with 2-ethoxyphenol showed an absorption maximum at 394.0 nm. The purified P450EP1Adegraded 2-ethoxyphenol in an assay system composed of spinach ferredoxin-NADP+oxidoreductase and NADPH. The reaction activity decreased to 1.4% of its original activity by addition of CO. The existence of catechol in the reaction mixture was confirmed after the metabolic reaction, indicating that P450EP1Acatalyzes O-dealkylation of 2-ethoxyphenol. In addition to 2-ethoxyphenol, the P450EP1Ametabolized 2-methoxyphenol, 1,1,1-trichloroethane, carbon tetrachloride, benzene, and toluene.Key words: cytochrome P450,Corynebacteriumsp., 2-ethoxyphenol, enzyme purification, biodegradation.

ISSN:0008-4166    

DOI:10.1139/w99-082

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Sphingomonasstrain UG30 mineralizes bothp-nitrophenol (PNP) and pentachlorophenol (PCP). Our current studies showed that UG30 oxidatively metabolized certain otherp-substituted nitrophenols, i.e.,p-nitrocatechol, 2,4-dinitrophenol (2,4-DNP), and 4,6-dinitrocresol with liberation of nitrite. 2,6-DNP,o- orm-nitrophenol, picric acid, or the herbicide dinoseb were not metabolized. Studies using14C-labelled 2,4-DNP indicated that in glucose-glutamate broth cultures of UG30, greater than 90% of 103 µM 2,4-DNP was transformed to other compounds, while 8-19% of the 2,4-DNP was mineralized within 5 days. A significant portion (20-50%) of the 2,4-DNP was metabolized to highly polar metabolite(s) with one major unidentified metabolite accumulating from 5 to 25% of the initial radioactivity. The amounts of 2,4-DNP mineralized and converted to polar metabolites was affected by glutamate concentration in the medium. Nitrophenolic compounds metabolized by UG30 were also suitable substrates for the UG30 PCP-4-monooxygenase (pcpBgene expressed inEscherichia coli) which is likely central to degradation of these compounds. The wide substrate range of UG30 could render this strain useful in bioremediation of some chemically contaminated soils.Key words: bioremediation, dinitrophenol, metabolism, nitroaromatic, pentachlorophenol,Sphingomonas.

ISSN:0008-4166    

DOI:10.1139/w99-083

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Mucosal immunity was established in the rat prostate by stimulating the common mucosal system through serosal exposure of formalin-killedEscherichia coli. Immunized but not sham-immunized rats developed bacterial specific IgG and IgA in prostatic fluid, and IgA in urine. Immunized (n= 21) and sham-immunized control rats (n= 30) were challenged by transurethral injection ofE. coliinto the prostate ducts. Mortality, gross and microscopic pathology, tissue bacterial counts, bacterial associated immunoglobulins, and antibody titers in serum and urine were assessed at 7 days following the challenge. IncreasedE. colispecific immunoglobulin titers were seen in immunized rats, andE. coli,but notProteus, found in the prostates of immunized animals were coated with IgG and IgA. Immunization protected against toxaemia and septicemia, seen as a rare complication of acute prostatitis, but did not protect against acute prostatitis, nor alter the degree of tissue damage seen in the rat model.Key words: prostatitis, mucosal immunity, rat model.

ISSN:0008-4166    

DOI:10.1139/w99-088

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The insect and plant pathogens within the fungal genusVerticilliumshowed enzymatic adaptation (production and regulation) directed to the degradation of some of the polymers found in the integument of their respective hosts. For example, the facultative plant pathogens (V. albo-atrumandV. dahliae) produced greater levels of cellulase and xylanase than the facultative insect pathogen (V. lecanii).Verticillium lecaniiproduced extracellular subtilisin-like protease when grown in insect cuticle medium but not in plant cell wall medium, while the plant pathogenV. albo-atrumshowed a diminished regulatory component in the production of this enzyme. The opportunistic pathogens (V. fungicolaandV. coccosporum) and the saprobic species (V. rexianum) were less specific in the production and regulation of several proteases as well as cellulases and xylanases. A dendrogram based on cluster analysis compiled from fungal API-ZYM profiles showed commonalties in a broad array of extracellular enzymes within a host-pathogen group (i.e. insect or plant pathogen). The opportunistic pathogens were dispersed throughout the dendrogram, suggestive of the diversity in type and expression of extracellular enzymes.Key words: extracellular enzymes, pathogenic fungi.

ISSN:0008-4166    

DOI:10.1139/w99-085

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Axenic culture of myxomycete plasmodia has been attempted from time to time by various authors, but with very little success. From over 500 known species of myxomycetes, fewer than 20 species have been reported in axenic culture to date, including axenic myxamoebal cultures. In these cultures, the plasmodia required either complex media, or a killed bacterial supplement for growth. Furthermore, the time required for attaining the axenic state varied from several months to years. In the present study, a simple, rapid procedure has been developed to render monoxenic plasmodial cultures axenic. This procedure is based on our discovery that plasmodia have certain unusual substrate preferences that are inhibitory to the associated bacteria usingPhysarella oblongaas a model. The presence or absence of the bacteria could be ascertained through incubation in four different bacteriological media and by the use of a differential staining technique.Key words: myxomycetes, axenic culture, hydrocarbon utilization, bacterial associates.

ISSN:0008-4166    

DOI:10.1139/w99-080

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A comparative study of visual and spectrophotometric MIC endpoint determinations for antifungal susceptibility testing ofAspergillusspecies was performed. A broth microdilution method adapted from the National Committee for Clinical Laboratory Standards (NCCLS) was used for susceptibility testing of 180 clinical isolates ofAspergillusspecies against amphotericin B and itraconazole. MICs were determined visually and spectrophotometrically at 490 nm after 24, 48, and 72h of incubation, and MIC pairs were compared. The agreement between the two methods was 99% for amphotericin B and ranged from 95 to 98% for itraconazole. It is concluded that spectrophotometric MIC endpoint determination is a valuable alternative to the visual reference method for susceptibility testing ofAspergillusspecies.Key words: antifungal, susceptibility testing,Aspergillus, spectrophotometric reading.

ISSN:0008-4166    

DOI:10.1139/w99-075

出版商:NRC Research Press    

年代:1999

数据来源: NRC