摘要:

Transformation of the plant growth promoting rhizobacteriumPseudomonas putidaGR12-2 with broad-host-range vectors can affect the growth of the bacterium, its ability to promote root elongation of canola seedlings under gnotobiotic conditions, and its persistence in soil. Plasmid transformants, and a transposon-mutagenized derivative ofP.putidaGR12-2, fell into two classes with respect to these three attributes: strains that were clearly diminished in these capabilities and strains that behaved like the nontransformed wild type. These differences can be accounted for by the imposition of a metabolic load that is created by some types of genetic modification that results in a physiological impairment of the modified bacterium and decreases its ability to function as a plant growth promoting rhizobacterium.Key words: plant growth promoting rhizobacteria, PGPR, bacterial fertilizer, soil bacteria, soil persistence, microcosm.

ISSN:0008-4166    

DOI:10.1139/m95-060

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Eukaryotic fimbriae are extracellular structures that have been shown to play a key role in mating and pathogenesis. Previous work has established that the major component of the fimbriae of the anther smut fungusMicrobotryum violaceum(Pers.) G. Deml & Oberw. (Ustilago violacea(Pers.) Rouss.) is a 74-kDa glycoprotein subunit. This study analyzes the carbohydrate moiety in the fimbrial subunit and reveals that it is composed of mannose and possibly some acetylated sugars that are anchored to an asparagine residue of the protein via twoN-acetylglucosamine residues. The carbohydrate component comprises 35% of the fimbrial subunit and the aglycone has an apparent molecular mass of 47 kDa. Using polyclonal antibodies, we have examined the conservation of the two components of the fimbrial subunits (protein and carbohydrate) in four divisions of fungi. Antibodies raised against native intact fimbriae ofM.violaceumdetected only the unique glycosylation pattern of these fimbriae, whilst antibodies raised against denatured fimbrial subunits were able to detect protein epitopes. Our results indicate that the fimbrial subunits ofM.violaceumare composed of a protein moiety that is highly conserved amongst fungal species and a carbohydrate moiety that has a pattern that is unique to members of the dicot-infecting smut fungi. The possible implications of a conserved glycosylation pattern and the limited host range of this phylogenetic line of smut fungi are discussed in relation to current attempts to reclassify these species into the taxon Microbotryales.Key words: fimbriae,Ustilago,Microbotryum, glycoprotein, antibodies, systematics, basidiomycetes.

ISSN:0008-4166    

DOI:10.1139/m95-061

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

ThelacZYgene cassette inserted into the chromosome ofPseudomonas aeruginosaUG2Lr andPseudomonas aureofaciensPs3732RNL11 was used as a genetic marker to study the fate of thePseudomonasstrains in river water microcosms. Expression of thelacZmarker in UG2Lr and Ps3732RNL11 was detected in microcosms containing as few as 12 and 14 colony-forming units (cfu)/mL of river water, respectively, by fluorimetric measurement of the β-galactosidase activity against 4-methylumbelliferyl-β-D-galactoside as the substrate. The persistence of andlacZexpression in thePseudomonasstrains were monitored in sterile and nonsterile river water in the presence and absence of added nutrients by dilution plating and fluorimetry, respectively. After incubation for 10 d at 10 °C, culturable populations of strain UG2Lr in sterile water samples, with and without nutrient added, decreased from an initial density of 1.5 × 104to 1.7 × 103and 4.6 × 103 cfu/mL, respectively. Despite similar numbers of UG2Lr cells in the two treatments, expression of thelacZmarker in the surviving cells of the nutrient-supplemented sample was 24 times higher than in the cells of the unamended sample. In nonsterile water samples, the density of UG2Lr declined to less than 6 cfu/mL in 30 d regardless of the nutrient conditions. A nutrient supplement increased the growth of the native bacterial population but did not enhance growth of andlacZexpression in the bacteria. Polymerase chain reaction analysis showed a decrease in amplification signal indicating a genuine decline in viable UG2Lr cell density in the water samples. Ps3732RNL11 cells established themselves in both sterile and nonsterile water samples. In nonsterile water samples, Ps3732RNL11 maintained a density of 20–40% of the culturable bacterial population. However,lacZexpression in both UG2Lr and Ps3732RNL11 cells was undetectable in nonsterile water samples after 30 d.Key words: survival, genetic marker,lacZexpression, polymerase chain reaction, recombinantPseudomonasstrains.

ISSN:0008-4166    

DOI:10.1139/m95-062

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

A mixed culture, isolated from soil contaminated with polycyclic aromatic hydrocarbons (PAHs), grew on and degraded fluoranthene in aqueous media supplemented with glucose, yeast extract, and peptone. Increased complex nitrogen levels in the medium promoted bacterial growth and a greater extent of fluoranthene degradation. Amendment of the media with high glucose levels also diminished specific fluoranthene degradation. The mixed culture was capable of degrading a range of other PAHs, including benzo[a]pyrene, anthracene, phenanthrene, acenaphthene, and fluorene. The mixed culture contained four predominant isolates, all of which were Gram-negative rods, three of which were identified asPseudomonas putida,Flavobacteriumsp., andPseudomonas aeruginosa. Better degradation of a defined PAH mixture was observed with the mixed culture than with individual isolates. A reconstituted culture, prepared by combining the four individual isolates, manifested a similar PAH biodegradation performance to the original mixed culture. When compared with the mixed culture, individual isolates exhibited a relatively good capacity to remove more water-soluble PAHs (acenaphthene, fluorene, phenanthrene, fluoranthene). In contrast, removal of less water-soluble PAHs (anthracene and pyrene) was low or negligible with isolated cultures compared with the mixed culture.Key words: polycyclic aromatic hydrocarbons, mixed culture, fluoranthene,Pseudomonas,Flavobacterium.

ISSN:0008-4166    

DOI:10.1139/m95-063

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The purpose of this study was to determine the ability of nonbasidiomycete soil fungi to oxidize pyrene (four rings) and benzo[a]pyrene (BaP) (five rings). Fungi were isolated from five different soils in which the polycyclic aromatic hydrocarbon content ranged from 0.8 to 80 μg/g dry soil. Approximately 50% of the isolates in all sites were able to oxidize pyrene. The pyrene-oxidizing species belonged to all fungal divisions except basidiomycetes. The most common werePenicilliumspp. of the subgenusFurcatumand these dominated the more contaminated soils.Penicillium janthinellumandSyncephalastrum racemosumexhibited the most rapid rates of pyrene oxidation. The major pyrene metabolites were identified by proton NMR and mass spectrometry as 1-pyrenol, 1,6- and 1,8-pyrenediol, and the 1,6- and 1,8-pyrenequinones. A high correlation was found between the ability to oxidize pyrene and BaP. As with pyrene, approximately 50% of the fungal isolates tested oxidized BaP to 9-hydroxy-BaP. Eighty percent of the pyrene-oxidizing strains were also able to metabolize BaP.Key words: fungi, polycyclic aromatic hydrocarbons, biotransformation, bioremediation, cytochrome P-450.

ISSN:0008-4166    

DOI:10.1139/m95-064

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

We studied the spatial-temporal dynamics of non-O1Vibrio choleraenumbers at a stabilization pond treatment plant. This bacterium's seasonal dynamics were the inverse of those of fecal coliforms, with high levels in hot periods and low levels in cold periods. Stabilization pond treatment did not significantly reduce non-O1V.choleraenumbers between the system's inflow and outflow points. In contrast, fecal coliforms were reduced by 98.95% in hot periods and by 94.91% in cold periods. Significant rho coefficient values for the Spearman correlation between numbers of non-O1V.choleraeand temperature and pH of 0.91 and 0.76, respectively, were found at the system's outflow point. An experimental study of the effects of pH, temperature, and sunlight on the survival of non-O1V.choleraeand fecal coliforms confirmed the inverse behaviour of the two bacterial groups noted in the stabilization ponds. Alkaline pH values of 8 and 8.8 promoted the survival of non-O1V.choleraeand inhibited that ofEscherichia coli. Low temperatures (8 °C) prolongedE.colisurvival (k = 0.002/h), while a temperature of 23 °C reduced it markedly (k = 0.022/h). Non-O1V.choleraedid not survive as well asE.coliat 8 °C (k = 0.009/h). The effect of temperature on non-O1V.choleraeappeared to be closely linked to nutrient levels. Non-O1V.choleraeappeared to be less sensitive to sunlight thanE.coliwhose survival was markedly reduced, particularly during summer periods. Non-O1V.choleraeandE.colidid not behave in the same way in water subjected to stabilization pond treatment. The use of fecal coliforms as an indicator of the potential health hazard of the effluent may not be adequate for this treatment procedure.Key words: stabilization pond, non-O1Vibrio cholerae,Escherichia coli, pH, temperature, sunlight.

ISSN:0008-4166    

DOI:10.1139/m95-065

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

To determine whether heat shock genes (hsp) were expressed in a stage-specific manner, total RNA was isolated from dormant pycnidiospores, germinating spores, and mature mycelium of representatives of two pathotypes ofLeptosphaeria maculans: the weakly virulent (or avirulent) and the virulent. Northern blots prepared by using total RNA isolated from normally grown and heat-shocked samples were hybridized with DNA ofhspgenes ofNeurospora crassa,hsp70,hsp80, and the heat shock inducible manganese peroxidase cDNA ofPhanerochaete chrysosporium. No hybridization signal was apparent in RNA from dormant spores in the absence of heat shock treatment, while heat shock treatment resulted in the induction of mRNA corresponding to these threehspgenes. In contrast, substantial amounts ofhsptranscripts were observed in germinating spores, even in the complete absence of externally applied stress. The mature mycelium failed to show these transcripts under normal growth conditions, but following exposure to hyperthermal treatment, a characteristic set of heat shock specific transcripts was witnessed. The two strains exhibited a similar pattern. Expression of the fungalhspgenes was also detectable in the plant tissue, following infection by both the virulent and weakly virulent strain. These data suggest that products of stress-responsive genes may have a role in an early event during spore germination.Key words: fungal phytopathogen, canola, fungal gene expression.

ISSN:0008-4166    

DOI:10.1139/m95-066

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

The objective of this work was to determine solution- and solid-phase alterations associated with galena (PbS) oxidation byThiobacillus ferrooxidansandThiobacillus thiooxidans. InT.ferrooxidansexperiments with 2.5–5% (w/v) galena, the pH remained almost constant at pH 2, whereas the pH increased in uninoculated controls. InT.thiooxidanscultures, the pH initially increased from 2 to 4. This initial increase was comparable to the pH change in an abiotic control, but the oxidation reaction inT.thiooxidanscultures subsequently became acid producing. Anglesite (PbSO4) was detected by X-ray diffraction as a solid-phase product of galena decomposition in both abiotic and inoculated experiments. When ferrous sulfate was added as a supplementary energy source forT.ferrooxidans, jarosite (MFe3(SO4)(OH)6) was detected as a new solid phase. Elemental S was not detected in the residues.Key words: anglesite, bioleaching of galena, galena oxidation, jarosite, lead sulfide oxidation,Thiobacillus ferrooxidans,Thiobacillus thiooxidans.

ISSN:0008-4166    

DOI:10.1139/m95-067

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Naphthazarin toxins ofFusarium solaniwere detected and quantified by competitive enzyme-linked immunosorbent assay (ELISA) in xylem fluid of scaffold roots from blight-diseased trees. These toxins alter plant metabolic activity; this study examined their effects on xylem health by measuring physiological components in xylem fluid. Protein concentration in fluid was positively correlated with increases in toxin concentration. In fluid containing about 100 μg∙L−1toxin, total amino acids reached levels 2.5 to 3.0 times greater than those in fluid containing no detectable toxin; asparagine, glutamic acid, proline, glycine, and arginine were the most abundant. Levels of phenylalanine ammonia-lyase, polyphenol oxidase, chlorogenic acid oxidase, and superoxide dismutase activity did not increase in xylem fluid containing toxin, which may be a reason why vascular discoloration did not occur. Xylem fluid containing about 20 μg∙L−1toxin was associated with a 9-fold increase in total phenolics and a 15-fold increase in peroxidase. Peroxidases were predominantly anionic and may function in defense. Some of these peroxidases may function as lignases, releasing phenolic and other constituents from cells and cell walls. These toxins are known to enhance membrane permeability, which may be the main reason for the accumulation of these stress metabolites in xylem fluid. These data explain the disruption of hydraulic conductivity in blight tree roots and the eventual physiological breakdown of roots on diseased trees.Key words: phytotoxins, isomarticin, ELISA, fungi, ro

ISSN:0008-4166    

DOI:10.1139/m95-068

出版商:NRC Research Press    

年代:1995

数据来源: NRC

摘要:

Mutations in theexeC-Noperon ofAeromonas hydrophila, which block extracellular protein secretion, also result in large decreases in the level of the major outer membrane porin, protein II. Immunoblot analysis demonstrated that the porin missing from the outer membrane of the mutant was not accumulating elsewhere in the cell. Pulse-chase and immunoprecipitation analyses showed that the porin was as stable in the mutant as in the wild type, but that far less porin was synthesized in theexemutants. The relationship between extracellular secretion involving theexegenes and the assembly of other outer membrane and surface proteins was also examined. Both the wild type andexeEmutants ofA.hydrophilawere capable of assembling the protein I and protein III porins under inducing conditions.Aeromonas sohriaAs9071, which contains a surface array protein, could secreteA.hydrophilaaerolysin and required homologues of theA.hydrophila exegenes to do so; however, anexe−derivative of this bacteria was unaffected in its ability to assemble its surface array. These results demonstrate that theexegenes are not required for general outer membrane protein assembly in these bacteria, but that the synthesis of protein II is specifically downregulated in theexemutants.Key words: extracellular secretion, outer membrane assembly, surface layer,Aeromonas.

ISSN:0008-4166    

DOI:10.1139/m95-069

出版商:NRC Research Press    

年代:1995

数据来源: NRC