ISSN:0008-4166    

DOI:10.1139/m96-099a

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

A strain ofPseudomonas marginalisPD-14B, isolated from polycyclic aromatic hydrocarbon (PAH) contaminated soil, produced an extracellular surface-active factor of high molecular weight containing protein and lipopolysaccharide. A crude preparation of the factor, obtained from the culture broth of cells grown in mineral salts (MS) medium with succinate and yeast extract, affected the extent of PAH degradation by the bacterial cells and prevented flocculation of PAHs in an aqueous suspension. A washed suspension ofP.marginaliscells also prevented flocculation of PAH suspensions and emulsified liquid hydrocarbons. Incubation of the factor and the factor-producing strain in the presence of different PAHs resulted in gradual increase of turbidity of the PAH dispersions. The factor markedly stimulated rate and extent of turbidity generation by bacterial cells. The surface-active factor may promote infection of lettuce and other plants by this known pathogen and may also have application in bioremediation.Key words: biosurfactant, polycyclic aromatic hydrocarbons,Pseudomonas marginalis, bioremediation, plant pathogenesis.

ISSN:0008-4166    

DOI:10.1139/m96-099

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The production of cold shock proteins (csps) and cold acclimation proteins (caps) was characterized in the psychrotrophic bacteriumPseudomonas putidaQ5 and its transconjugantP.putidaQ5T which contains the toluene-degradative TOL (pWWO) plasmid, using two-dimensional gel electrophoresis and computing scanning laser densitometry. Similar growth rates for the psychrotrophic bacteriumP.putidaQ5 and the transconjugant were found at temperatures ranging from 30 to 0 °C. Sixteen proteins were quantified and compared inP.putidaQ5 andP.putidaQ5T following a 25 to 5 °C cold shock or constant growth at 5 °C. During constant growth at 25 °C, a decrease in the synthesis of various proteins occurred in the transconjugant. Following cold shock to 5 °C or constant growth at 5 °C, csps and caps were produced with a greater number occurring in the transconjugant. This may suggest an additional stress response in the transconjugant owing to metabolic load exerted by the TOL plasmid. Growth ofP.putidaQ5T with toluate produced seven proteins that appeared to be TOL-plasmid mediated and of which some were also designated as caps.Key words: cold shock proteins, cold acclimation proteins, TOL pWWO plasmid, psychrotrophic bacterium.

ISSN:0008-4166    

DOI:10.1139/m96-100

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The esterases from the cell-free extracts (CFEs) ofAspergillus parasiticusATCC15517, an aflatoxin-producing strain, catalyzing the hydrolytic conversion of versiconal hemiacetal acetate (VHA) to versiconal was biochemically studied. The specific activity of the enzymes increased 2.5-fold during incubation of mycelia through 40–55 h. No metal ions were required for enzyme stability, but EDTA at 1 mM and dithiothreitol at 0.5–5 mM increased its stability. Three peaks of VHA esterase activity were resolved when the proteins in the CFEs prepared from the mycelia of different ages were separated by anion-exchange column chromatography, suggesting that at least three VHA esterases were present in the eluate of this purification step. One of these esterases extracted from the mycelia of a 55-h culture was partially purified in five steps by means of preparative chromatography and fast protein liquid chromatogaphy. The partially purified enzyme when reacted with [14C]diisopropylfluorophosphate followed by sodium dodecyl sulfate – polyacrylamide gel electrophoresis gave a single radiolabelled band, which corresponded to a protein of 32 kDa. The molecular mass of the partially purified VHA esterase determined with gel filtration was around 60 kDa. The results suggested that the enzyme consists of two isomeric subunits.Key words: aflatoxin biosynthesis, esterase, versiconal hemiacetal acetate,Aspergillus parasiticus.

ISSN:0008-4166    

DOI:10.1139/m96-101

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The decontamination ofLegionella pneumophilaand other heterotrophic microbes by heat flushing in four legionellae-positive hot water systems was studied. Before the decontamination procedure, the concentration of legionellae varied from 3.0 × 10−3to 3.5 × 10−5 cfu/L and the hot water temperature from 43.6 to 51.5 °C. During the contamination the temperature was raised to 60–70 °C. All taps and showers were cleaned from sediments and flushed with hot water twice a day for several minutes. The decontamination lasted for 2–4 weeks. In a few weeks the heat-flushing method reduced the concentration of legionellae below the detection limit (50 cfu/L) in the hot circulating water system just before and after the heat exchanger. The high hot water temperature also decreased the viable counts of heterotrophic bacteria, fungi, and total microbial cells determined by the epifluorescent microscopy. However, the eradication of legionellae failed in a water system where the water temperature remained below 60 °C in some parts of the system. After the decontamination, the temperature of hot water was lowered to 55 °C. Thereafter, all the studied hot water systems were recolonized by legionellae within a few months, showing that the decontamination by heat flushing was temporary. Also, the contamination of other bacteria increased in a few months to the level before decontamination.Key words: legionellae, hot water system, decontamination, water temperature, heterotrophic bacteria.

ISSN:0008-4166    

DOI:10.1139/m96-102

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The aim of this study was to assess whether isozyme polymorphism in different members of theMorchellaceaecould be used to improve the systematics in this fungal group and to characterize intraspecific crossings between monosporal strains inMorchella esculenta. For this purpose, isozyme electrophoretic analysis of the following enzymes was performed: glutamine synthetase, NAD–glutamate dehydrogenase, NADP–glutamate dehydrogenase, aspartate aminotransferase, malate dehydrogenase, NAD–glyceraldehyde phosphate dehydrogenase, glucose phosphate isomerase, and superoxide dismutase. The analyses allowed discrimination at the inter- or intra-specific levels and could help to establish a method of identification for strains in theMorchellaceae. To a certain extent they appeared to be suitable to analyze interactions of monosporal strains ofMorchella esculentain pairing experiments. The polymorphism shown in this study was consistent with the phylogenetic relationships between the investigated strains only at the genus level.Key words: isozyme analysis, electrophoresis,Morchellasp., polymorphism.

ISSN:0008-4166    

DOI:10.1139/m96-103

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

3-Acetyldeoxynivalenol is the major trichothecene produced by the fungusFusarium culmorum. Studies in vivo withF.culmorumhave established the following biosynthetic precursors of 3-acetyldeoxynivalenol: isotrichool → isotrichodiol → isotrichodermin → 15-deacetylcalonectrin, 7α-hydroxyisotrichodermin, 8α-hydroxyisotrichodermin → calonectrin → deoxynivalenol. In this paper, we describe in vitro investigations of one of these metabolic steps. The cell-free system ofF.culmorumthat converts isotrichodermin into 15-deacetylcalonectrin, 7α-hydroxyisotrichodermin, and 8α-hydroxyisotrichodermin is described here. This preparation requires NADPH but not NADH for activity and is not inhibited by carbon monoxide, cyanide, or known oxygenase inhibitors, such as SKF-525-A or ancymidol.Key words: trichothecene,Fusarium culmorum, cell-free system, isotrichodermin, 15-deacetylcalonectrin.

ISSN:0008-4166    

DOI:10.1139/m96-104

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The antitumor drug bleomycin can produce a variety of lesions in the cellular DNA by a free radical dependent mechanism. To understand how these DNA lesions are repaired, bleomycin-hypersensitive mutants were isolated from the yeastSaccharomyces cerevisiae. We report here the analysis of one mutant, DRY25, that showed extreme sensitivity to bleomycin. This mutant also exhibited hypersensitivity to hydrogen peroxide andt-butyl hydroperoxide, but showed no sensitivity to other DNA-damaging agents, including γ-rays, ultraviolet light, and methyl methanesulfonate. Subsequent analysis revealed that strain DRY25 was severely deficient in the repair of bleomycin-induced DNA lesions. Under normal growth conditions, DRY25 displayed a 3-fold increase in the frequency of chromosomal translocation that was further stimulated by 5- to 15-fold when the cells were treated with either bleomycin or hydrogen peroxide, but not by methyl methanesulfonate, as compared with the wild type. Genetic analysis indicated that the mutant defect was independent of the nucleotide excision, postreplication, or recombinational DNA-repair pathways. These data suggest that one conceivable defect of DRY25 is that it lacks a protein that protects the cell against oxidative damage to DNA. A clone that fully complemented DRY25 defect was isolated and the possible roles of the complementing gene are discussed.Key words: yeast, bleomycin, DNA repair, mutations.

ISSN:0008-4166    

DOI:10.1139/m96-105

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Common bean (Phaseolus vulgarisL.) is a traditional crop in much of Latin America, where it is often planted into soils containing numerous, sometimes ineffective, indigenous rhizobia. The presence of these indigenous organisms can limit response to inoculation. Because of this, we have sought bean cultivars that will nodulate preferentially with the inoculant strain, and have previously reported on the preference between the bean cultivar RAB39 and strains ofRhizobium tropici. We have detailed this interaction using the inoculant-quality strain UMR1899. In the present study the root tip marking (RTM) technique was used to demonstrate that this preference in nodulation was evident, even when inoculation with UMR1899 was delayed up to 8 relative to that withRhizobium etliUMR1632. In contrast to studies with other legumes, roots of RAB39 were not predisposed to nodulate with UMR1632, even though preexposed to this strain for considerable periods of time. The presence of UMR1899 actually reduced nodulation by UMR1632 substantially, even when inoculation with UMR1899 was significantly delayed. When UMR1899 and UMR1632 were applied to separate halves of a split-root system, the number of nodules on the side receiving UMR1632 was less than for the half root inoculated with UMR1899, but the differences were not significant. This suggests that the preference response is not systemic but requires proximity between the strains involved. UMR1899 produced more than 50% of the nodules even when the ratio of UMR1632:UMR1899 in the inoculant was 10:1. The results are further evidence of a stable and marked preference of RAB39 for UMR1899, which warrants a more detailed study at the field level.Key words:Phaseolus vulgarisL., common bean, delayed inoculation, strain preference, cell proportions.

ISSN:0008-4166    

DOI:10.1139/m96-106

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The biotransformation of 3,4-methylenedioxy-N-methylarnphetamine (MDMA) and 3,4-methylenedioxyamphetamine (MDA) was examined in the fungusCunninghamella echinulata. In addition to the reported mammalian metabolites (MDA, 3,4-methylenedioxybenzyl methyl ketoxime, 3,4-methylenedioxybenzyl methyl ketone) and the parent substrate, there were six novel metabolites detected.N-Acetyl-3,4-methylenedioxyamphetamine (NAcMDA) was unequivocally identified and three unidentified metabolites related to NAcMDA were also detected.N-Acetyl-3,4-methylenedioxy-1-phenyl-1-hydroxy-2-aminopropane was tentatively identified as a metabolite of MDMA. The only metabolite of MDA identified was NAcMDA. Two metabolites related to MDA remain unidentified.Key words:Cunninghamella, amphetamine, biotransformation, 3,4-methylenedioxy-N-methylamphetamine, 3,4-methylenedioxyamphetamine.

ISSN:0008-4166    

DOI:10.1139/m96-107

出版商:NRC Research Press    

年代:1996

数据来源: NRC