摘要:

The accumulation of both activity and protein of a methyltransferase (MTase) fromAspergillus parasiticus, which catalyzes conversion of sterigmatocystin toO-methylsterigmatocystin in the aflatoxin pathway, was detected in fungal mycelia slightly before the onset of aflatoxin biosynthesis in the same cultures. MTase protein was identified in mycelial postmicrosomal (soluble protein) fractions by electrophoresis and subsequent immunoblotting using antiserum raised against purified MTase protein; MTase activity was determined by measuring the rate of conversion of sterigmatocystin toO-methylsterigmatocystin in the presence of soluble protein fractions. Using the above technique, it was determined that MTase protein as well as MTase activity increased sharply in mycelia 30 to 45 h after inoculation, shortly after which, mycelial growth rate began to decline. During the subsequent time interval (45 to 70 h after inoculation), a sharp increase in aflatoxin levels was detected in the culture medium. Results obtained from an experiment in which cycloheximide was added to cultures at various times to inhibit protein synthesis and from an experiment in which mycelial proteins were radiolabelled to identify newly synthesized proteins indicated that accumulation of MTase activity and protein in late growth phase mycelia is due tode novoprotein synthesis.Key words: aflatoxin, methyltransferase, biosynthetic pathway.

ISSN:0008-4166    

DOI:10.1139/m90-001

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Protoplasts from two auxotrophic mutants ofTrichoderma harzianumRifai (ATCC 32173), obtained from young thalli following cell wall digestion by NovoZym 234, were fused in 33% PEG suspended in 10 mM Tris-HCl and 10 mM CaCl2, pH 7.5. The frequency of fusion between lysine- and arginine-requiring auxotrophs resulting in prototrophic strains was about 5%. These prototrophic strains were classified into parental and nonparental types. Colonies developed from single conidia of the nonparental phenotype exhibited prototrophic parental or recombinant phenotypes. The ability of both prototrophic and parental strains to overgrow the soil-borne pathogenic fungiRhizoctonia solani,Sclerotium rolfsii, andPythium aphanidermatumin dual cultures was used to evaluate their antagonistic capability. The antagonistic abilities of the prototrophic strains were found to vary with each pathogenic fungus. The prototrophic strain A2 overgrew all the pathogenic fungi more rapidly than the parental strains. Strain A2 effectively controlledRhizoctoniadamping-off of cotton seedlings, in the greenhouse, when compared with the parental strains. Protoplast fusion appears to be a useful tool for combining desirable traits from parental strains to produce improved biocontrol strains.Key words:Trichoderma harzianum, biocontrol, protoplast fusion.

ISSN:0008-4166    

DOI:10.1139/m90-002

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The mechanism(s) involved in the effect ofAzospirillum brasilensestrain Cd on root susceptibility to nodulation was studied in medic seedlings grown in pouches. The number of nodules above the position of the root-tip mark at the time of inoculation and the position of the uppermost nodule were used as parameters for determining the rate of nodule initiation. Cell-free extracts and culture supernatants prepared fromAzospirillumand the cytokinin benzyladenine (10−9 M) significantly increased the number of nodules formed above the root-tip mark when applied together withRhizobiumcompared with those formed withRhizobiumalone. The application of indoleacetic acid did not cause an increase in the number of nodules. In the absence ofRhizobium, exposure toAzospirillumat a concentration of 109 cfu/mL or to compounds excreted by the bacteria into the growth medium caused a 40% increase in endogenous ethylene production by the roots. A less concentrated inoculum did not increase ethylene production. Inoculation withAzospirillumsignificantly increased the specific activity of the enzymes glucose-6-phosphate dehydrogenase,L-phenylalanine ammonia-lyase, and shikimate dehydrogenase compared with roots inoculated withRhizobiumalone.Key words:Azospirillum,Rhizobium,Medicago polymorpha, root morphology, nodule initiation.

ISSN:0008-4166    

DOI:10.1139/m90-003

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

The relationship between chemical structure and the enhancement of microbial degradation of three benzimidazole compounds in soil was determined. Preapplication of methyl benzimidazole-2-ylcarbamate (carbendazim or MBC), 2-aminobenzimidazole (2AB), and benzimidazole enhanced their degradation upon repeated application (self-enhanced degradation). MBC and 2AB cross-enhanced the degradation of each of these two compounds, whereas benzimidazole did not enhance the degradation of MBC. Thiabendazole (TBZ) did not enhance its own degradation or cross-enhance the degradation of MBC. No increase in the number of MBC-degrading fungi or in the capacity of soilborne fungi to degrade MBC was detected in soil exhibiting enhanced MBC degradation (MBC-history). A sharp increase in esterolytic activity in the microsomal fraction ofAlternaria alternatacapable of degrading MBC in culture was induced by the presence of MBC in the growth medium. 2AB was the main metabolite of MBC that accumulated inA.alternatacultures and in cell-free preparations. MBC was degraded much faster by mixed bacterial cultures that originated from MBC-history soil than in cultures from MBC-nonhistory soil. Fluctuations in the MBC degrading capacity of mixed bacterial cultures occurred during repeated subculturing of the mixed culture. Inoculation of nonhistory soil with mixed bacterial cultures resulted in enhanced MBC degradation, whereas inoculation withA.alternatadid not enhance MBC degradation. It is suggested that while fungi contribute to MBC dissipation in soil, bacteria have a greater role in enhanced biodegradation of MBC in soil.Key words: accelerated degradation, fungicide, problem soils.

ISSN:0008-4166    

DOI:10.1139/m90-004

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Restriction endonuclease fingerprinting (REF) analysis was used to examine total cellular DNA prepared from 56 independent field isolates of the fish pathogen,Aeromonas salmonicida. DNA was digested singly with the restriction enzymesEcoRI andHindIII, and the resulting fragments separated by polyacrylamide gel electrophoresis and visualized by silver staining. The REF patterns of typical isolates ofA.salmonicidasubsp.salmonicidawere distinct from those ofA.hydrophila,A.salmonicidasubsp.achromogenes,A.salmonicidasubsp.masoucida, and atypical isolates ofA.salmonicidasubsp.salmonicida. Differences between strains of typicalA.salmonicidasubsp.salmonicidacould also be distinguished. Canadian isolates examined could be assigned to 1 of 12 different groups (REF groups), with the majority of the isolates belonging to REF groups 1 and 5. REF group 1 strains were isolated from British Columbia and New Brunswick while REF group 5 isolates were found in Ontario. None of the European strains examined had REF patterns identical to those of Canadian isolates. Based on REF analysis, there was little genetic heterogeneity detected among 23 isolates from two short-term studies of naturally occurring infections. Several different REF groups were seen amongA.salmonicidacollected over a 10-year period from coho salmon from the Credit River. Consistent with earlier biochemical and hybridization studies, the REF data suggest thatA.salmonicidais a clonal pathogen. REF analysis can, however, permit the identification of subgroups, which may be useful in epidemiological studies.Key words:Aeromonas salmonicida, restriction fragment length polymorphism, restriction endonuclease fingerprinting, furunculosis, epidemiologic method.

ISSN:0008-4166    

DOI:10.1139/m90-005

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Two fractions exhibiting acid protease activity (AFPI and AFPII) were isolated by extraction of membrane vesicles ofAspergillus fumigatuswith Triton X-100. These two fractions produced single bands in both polyacrylamide and sodium dodecyl sulfate polyacrylamide gel electrophoresis and showed apparent molecular weights of 73 000 and 43 000, respectively. Molecular weights determined by gel filtration in the absence and presence of Triton X-100 and sedimentation velocities in analytical ultracentrifugation indicated hydrophobic characteristics, since both fractions readily aggregated and complexed with Triton X-100; both exhibited elevated enzyme activities in the presence of Triton X-100. Carbohydrate content was 93% for AFPI and 85% for AFPII. The enzymatic fractions demonstrated different pH optima in the acid range as well as different temperature stabilities. Both protease fractions cross reacted in double immunodiffusion, while in crossed immunoelectrophoresis both demonstrated five precipitin peaks, each with similar patterns. AFPI demonstrated two additional precipitin peaks in crossed immunoelectrophoresis. As determined by crossed immunoaffinoelectrophoresis, the protease fractions demonstrated galactose and mannose residues. In biotin–avidin enzyme-linked immunosorbent assay both fractions reacted with allergic bronchopulmonary aspergillosis and aspergilloma sera. It can be concluded that the two fractions with protease activity ofA.fumigatusreported here may be of significance inAspergillus-induced diseases.Key words:Aspergillus, membrane, allergens, proteases, aspergillosis.

ISSN:0008-4166    

DOI:10.1139/m90-006

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Eighteen isolates ofGiardia duodenalisfrom animal and human sources were studied for protein differences by polyacrylamide gel electrophoresis and for antigenic differences by immunoblot analysis. The polyacrylamide gels showed that whilst the isolates were for the most part homogeneous in their protein banding patterns, some isolates did show some differences. The immunoblot analysis yielded many bands, including prominent bands of 32 and 66 kilodaltons. Five of the six isolates that showed differences in protein banding pattern also showed differences in antigenic reactivity. Our findings suggest that differences can be seen with the use of immunoblotting and that this technique is a tool that may be useful for isolate differentiation when used in conjunction with other techniques.Key words:Giardia, giardiasis, characterization, immunoblot.

ISSN:0008-4166    

DOI:10.1139/m90-007

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Annual variations of vibrios able to proliferate at 37 °C have been studied in various conditions: in urban waste water discharged in the Toulon harbour, in mussels subjected or not to those discharges, and in seawater far from the waste water effluent (for reference). Mean concentration values were nearly similar in the effluent and seawater samples, in the order of 500 bacteria/100 mL, and 400 bacteria/mL in ground mussels, with concentrations showing great variability. In all cases, seasonal abundance fluctuations occurred, with a minimum in winter. A total of 214 vibrio strains were analyzed and identified. The effluent population was the most diversified, including several species of sanitary interest such asVibrio fluvialis(29.3%),V.cholerae(non O1) (13.4%), andV.metschnikovii(11.0%), as well as other species more typically marine, notablyV.alginolyticus(11.0%). In seawater, the latter species was largely represented (48.6%), but other representatives of this genus were also present, such asV.harveyi,V.campbellii, orV.fishcheri; no strain ofV.metschnikoviiwas isolated. The specific composition of the population associated with mussels was similar to that found in seawater.Key words: vibrios, urban sewage, mussels, seawater, annual fluctuations. [Journal translation]

ISSN:0008-4166    

DOI:10.1139/m90-008

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

An intracellular β-1, 4-D-glucosidase (EC 3.2.1.21) was isolated from the mutant strain HP-3 ofStreptomyces lividans66 which produced about 12 times more enzyme than the wild-type strain. The purification was carried out by anion exchange column chromatography followed by high-performance liquid chromatography on DEAE and on molecular sieve columns. The enzyme is glycosylated and has an apparent Mrof 51 000 and a pI of 4.3. Its activity was optimal at pH 6.5 and at a temperature of 40 °C. TheKmand theVmaxon cellobiose were 3.1 mM and 65.6 μmol min−1mg−1of enzyme.Key words: β-glucosidase,Streptomyces lividans, purification, characterization.

ISSN:0008-4166    

DOI:10.1139/m90-009

出版商:NRC Research Press    

年代:1990

数据来源: NRC

摘要:

Of 24 bacterial species examined for lisinopril refractive peptidyl dipeptidase activity, only 8 contained activity. Activity inPseudomonas maltophiliawas more than fourfold higher than that of any other species.Pseudomonas maltophiliamay be unique among bacteria in possessing high peptidyl dipeptidase activity that is both EDTA inhibitable and lisinopril resistant.Key words:Pseudomonas maltophilia, peptidyl dipeptidase.

ISSN:0008-4166    

DOI:10.1139/m90-010

出版商:NRC Research Press    

年代:1990

数据来源: NRC