摘要:

Thirteen resin acid degrading bacteria enriched on abietic or dehydroabietic acids were isolated from waste water from the aerated stabilization basin of a bleached kraft pulp mill. Standard biochemical tests were used to characterize each isolate. Each isolate was tested for its ability to degrade six abietane- and pimarane-type resin acids. Resin acid concentrations were determined by high pressure liquid chromatography and UV absorbance. Cluster analysis based on phenotypic characteristics identified two distinct clusters of degraders that differed in their ability to utilize carbohydrates as carbon sources. Fatty acid methyl ester analysis of representative isolates from each cluster identified A19-6a and D11-13 asComamonasandAlcaligenesspecies, respectively. To determine genotypic relatedness, enterobacterial repetitive intergenic consensus sequences were used to amplify genomic DNA fragments from 10 isolates. These results supported the phenotypic analysis for all isolates tested except A19-5 and A19-6b. These two organisms were clustered closely together based on phenotype but had distinctly different banding patterns, suggesting that they are not related genotypically. All isolates degraded a subset of the six resin acid congeners. Isolates A19-3, A19-6a, A19-6b, and D11-37 were the most effective at degrading all six congeners.Key words: biodegradation, resin acids, metabolism,Comamonas,Alcaligenes.

ISSN:0008-4166    

DOI:10.1139/m96-058

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The fermentation of cellobiose is a rare trait among yeasts. Of the 308 yeast species that utilize cellobiose aerobically, only 12 species ferment it, and only 2 species,Candida molischianaandCandida wickerhamii, also ferment cellodextrins.Candida molischianaproduced β-glucosidase activity on all carbon sources tested, except glucose, mannose, and fructose. When these sugars were added to cultures growing on cellobiose, the synthesis of β-glucosidase ceased. However, the total amount of enzyme activity remained constant, indicating that theC.molischianaβ-glucosidase is catabolite repressed and not catabolite inactivated. When grown in medium initially containing glucose plus xylose, cellobiose, maltose, mannitol, or glucitol,C.molischianapreferentially utilized glucose and produced little β-glucosidase activity until glucose was nearly depleted from the medium. When grown in medium containing cellobiose plus either fructose or mannose, the yeast preferentially utilized the monosaccharides and produced little β-glucosidase activity.Candida molischianaproduced β-glucosidase and co-utilized cellobiose and xylose, maltose, or trehalose. Glucose and fructose, mannose, or trehalose were co-utilized; however, no β-glucosidase activity was detected. Thus, the order of substrate preference groups appeared to be (glucose, trehalose, fructose, mannose) > (cellobiose, maltose, xylose) > (mannitol, glucitol).Key words: glucose repression, trehalase, diauxic utilization, yeast.

ISSN:0008-4166    

DOI:10.1139/m96-059

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Extracellular phenol oxidase activity was characterized and compared inPyricularia oryzaewild-type and albino cell types to determine if this phenol oxidase was responsible for lack of melanization in the albino culture. Filtrates of the albino mutant Alb-5 showed activity similar to those of the wild type, while those of a buff mutant (Cp62) showed weak phenol oxidase activity. This indicated that the lack of melanization in the albino mutant was not due to an absence of phenol oxidase activity. The phenol oxidase isoform patterns from the wild type and two mutants were similar when analyzed by polyacrylamide gel electrophoresis. The slowest migrating isoform of phenol oxidase from wild-typePyricularia oryzaewas the major form and had a molecular mass of 380 kDa. The molecular masses of two of the minor forms were 220 and 130 kDa. The isoforms oxidized 1,8-dihydroxynaphthalene, the terminal metabolite in the polyketide pathway to melanin. The major phenol oxidase isoform was also present in extracts from albino mutants and the buff mutant. The major form was enriched by a combination of ammonium sulfate precipitation, DEAE-Sepharose column chromatography, and elution from preparative polyacrylamide gels. The enriched isoform of phenol oxidase separated into two forms after a second electrophoresis, indicating that these two isoforms interconvert. Analysis of both forms by sodium dodecyl sulfate – polacrylamide gel electrophoresis indicated that both were composed of a single subunit with a molecular mass of 70 kDa. The enriched isoform preferred phloroglucinol as a substrate and had a Michaelis constant (Km) of 19.3 mM for phloroglucinol and a pH optimum between 6 and 7.5.Key words: phenol oxidase, laccase,Pyricularia oryzae, rice blast, melanin.

ISSN:0008-4166    

DOI:10.1139/m96-060

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The continuous cultivation technique was used to investigate the screening for lipase-producing microorganisms from four commercial starters suitable for the degradation of domestic wastes. Using this technique, three strains of lipase-producing bacteria were isolated and identified:Pantoea agglomerons(BB96CC1, BB168CC2) andPseudomonas fluorescens(BW96CC1). In addition, butter fat induced more lipase production when present in the growth medium. Interesterification of butter fat triacylglycerols by enzymatic extracts of the isolated strains of microorganisms resulted in an appreciable interesterification yield, implying that hydrolysis was suppressed and interesterification of butter fat triacylglycerols was maximized in a microemulsion free-cosurfactant system.Key words: continuous culture, screening, interesterification, lipases, butter fat.

ISSN:0008-4166    

DOI:10.1139/m96-061

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Fibrobacter succinogenespossesses seven cellulose-binding proteins (CBPs) of 40, 45, 50, 120, 180, 220, and 240 kDa. The 120-, 180-, 220-, and 240-kDa proteins were present in the outer membrane (OM), while the 40-, 45-, 50-, and 120-kDa proteins were either periplasmic or peripheral membrane proteins. The 120-kDa CBP, which was identified as endoglucanase 2, was a major component in both the OM and periplasm. Zymogram analysis for glucanases showed that the major membrane-associated CBPs, with the exception of endoglucanase 2, lacked endoglucanase activity. Affinity-purified antibodies against the 180-kDa CBP cross-reacted strongly with numerous cell envelope proteins of higher and lower molecular mass, including the previously characterized chloride-stimulated cellobiosidase. Treatment of the 180-kDa CBP and cell envelope proteins with periodate resulted in almost complete loss of antibody binding, suggesting that they possessed a common epitope that was carbohydrate in nature. Immunogold labelling of whole cells using antibodies against the 180-kDa CBP demonstrated that either the 180-kDa CBP or related proteins with a cross-reactive epitope were located at the cell surface. These epitopes were distributed uniformly on cells not bound to cellulose but congregated on the cell surface at sites of adhesion of cells to cellulose. Antibodies to the 180-kDa protein caused 62% inhibition of binding ofF.succinogenesto crystalline cellulose, which provides evidence that either the 180-kDa CBP and (or) other related cross-reactive surface proteins have a role in adhesion to cellulose.Key words: cellulose, adhesin, adhesion, binding,Fibrobacter,succinogenes, rumen.

ISSN:0008-4166    

DOI:10.1139/m96-062

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Fimbriae of the anther smut fungus,Microbotryum violaceumare polymers of six 74-kDa glycoprotein isoforms. Digestion of fimbrial monomers with α-mannosidase yielded two polypeptides with masses of 70 and 48 kDa. The 70-kDa polypeptide is probably a product of incomplete digestion and the 48-kDa polypeptide is the aglycone. Thus, most of the carbohydrate component of fimbrial protein is mannose. Previous observations have suggested that fimbriae are necessary for mating inM.violaceum. Further evidence for this role was obtained in the present study by showing that mating is inhibited by an anti-fimbrial protein antiserum, by mannose and related sugars glucose and arabinose, and by the lectin concanavalin A. Since inhibition was not complete, however, two mechanisms for adhesion between compatible cells were proposed, one fimbrial dependent and one independent. Lastly, fimbrial protein froma1but nota2mating types bound to a mannose–agarose column, suggesting a lectin-like capability. The fimbrial dependent mechanism of cell-to-cell adhesion may involve binding of the mannose residues of the fimbriae ofa2cells by the fimbriae ofa1cells.Key words: mating,Microbotryum violaceum, lectin, fimbriae.

ISSN:0008-4166    

DOI:10.1139/m96-063

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

TherpoN(ntrA) gene (encoding sigma 54) ofAzospirillum brasilenseSp7 was isolated by using conservedrpoNprimers and the polymerase chain reaction, and its nucleotide sequence was determined. The deduced amino acid sequence of the RpoN protein was found to share a high degree of homology with other members of the sigma 54 family. Two additional open reading frames were found in theAzospirillum brasilense rpoNregion, with significant similarity to equivalent regions surrounding therpoNlocus in other bacteria. AnrpoNmutant ofAzospirillum brasilenseSp7 was constructed by gene replacement and found to be defective in nitrogen fixation, nitrate assimilation, and ammonium uptake. Lack of ammonium uptake was also found in previously isolatedAzospirillum brasilense ntrBandntrCmutants, further supporting the role of thentrsystem in this process. In addition, therpoNmutant was found to be nonmotile, suggesting a role of RpoN inAzospirillum brasilenseflagellar biosynthesis.Key words:Azospirillum brasilense, sigma factor, nitrogen fixation, ammonium assimilation, motility.

ISSN:0008-4166    

DOI:10.1139/m96-064

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Pseudomonas aeruginosaandCandida albicanswere reported to adhere to the glycosphingolipid asialo-GM1by means of pili and fimbriae, respectively. These diverse adhesins have been previously reported to have an immunologically conserved antigenic epitope and the role of this cross-reactive epitope in adherence to asialo-GM1 was investigated in this study. Both the unbiotinylated PAK pilus and fimbrial adhesins inhibited biotinylated pili fromP.aeruginosaPAK and biotinylatedC.albicansfimbriae binding to asialo-GM1and receptors present on human buccal epithelial cells (BECs), which suggested that the same receptor sites were recognized by the two adhesins. Monoclonal antibodies PK99H and Fm16 raised against theP.aeruginosaPAK pili andC.albicansfimbriae, respectively, recognized a conserved epitope present on the two adhesins. Both Fm16 and PK99H blocked fimbriae binding to asialo-GM1and BEC receptors and also inhibitedP.aeruginosaandC.albicanswhole cell binding to BECs. These data suggested that the conserved epitope confers receptor-binding properties to the adhesins, demonstrated that (i) asialo-GM1-like receptors present on epithelial cell surfaces are utilized by the pilus and fimbrial adhesins and (ii) the binding to these glycoreceptors is mediated by a conserved epitope that has receptor-binding properties.Key words: adhesins, pilus, fimbria, receptors.

ISSN:0008-4166    

DOI:10.1139/m96-065

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Ninety-three strains ofStreptomyceswere isolated from lenticels of potato tubers grown in naturally disease-suppressive and disease-conducive soils. Twenty-two strains showed more antibiotic activity against virulentStreptomyces scabiesRB3II than the standard pathogen-suppressive strains PonR and PonSSII. These 22 suppressive strains were non-pathogenic on leaf-bud tubers in the greenhouse. These suppressive strains plus standard strains PonR and PonSSII, 4 Minnesota (MN) virulentS.scabiesstrains, 11 virulentS.scabiesstrains, and 2 virulentStreptomyces acidiscabiesstrains from the eastern United States were evaluated in all possible paired combinations for antibiotic activity and competitive interactions in antibiotic and co-plating assays. A significant positive correlation between the ability of a strain to inhibit others and the ability of that strain to resist inhibition was observed in antibiotic assays (r = 0.6,P < 0.01). On average, suppressive strains inhibited other strains more and were less inhibited by other strains than virulent strains. Suppressive strains significantly reduced scab and did not affect tuber yield in a field-pot test. Taxonomic tests were used to characterize theStreptomycesstrains used in this study. All the virulent strains and 54% of suppressive strains were classified asS.scabies.Key words:Streptomyces, suppressive soil, potato scab.

ISSN:0008-4166    

DOI:10.1139/m96-066

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

A DNA probe containing the structural gene for dicarboxylate transport (dctA) ofRhizobium melilotihybridized strongly with the fragments ofAzospirillum lipoferumgenomic DNA. A genomic library ofA.lipoferumwas screened for thedctAgene by complementation of adctAmutant ofRhizobium meliloti. A recombinant cosmid, p37D, capable of restoring growth of thedctAmutant on dicarboxylates was isolated and found to hybridize to thedctAprobe. The ability of p37D to complement thedctBmutant ofR.melolitiindicated thatdctAanddctBgenes inA.lipoferummay be organized adjacent to each other.Key words:Azospirillum lipoferum, dicarboxylate transport gene, complementation cloning.

ISSN:0008-4166    

DOI:10.1139/m96-067

出版商:NRC Research Press    

年代:1996

数据来源: NRC