摘要:

Five yeast extracts (YE) were fractionated by ultrafiltration (UF) with 1, 3, and 10 kDa molecular weight cutoff membranes, concentrated by freeze-drying, and the resulting powders of yeast extract filtrates (YEF) were evaluated for their growth-promoting properties on nine cultures of lactic acid bacteria (LAB). There was an increase in &agr;-amino nitrogen content of the YEF powders as the pore size of the UF membranes used to filter the YE solutions decreased. The source of YE had a much greater effect than UF on the growth of LAB. This was also the case for the YEF contents in total and &agr;-amino nitrogen. Growth curves of the LAB showed that maximum growth rate (&mgr;max) data were on average 30% higher with bakers' YE than with brewers' YE, while maximum optical density (ODmax) values were on average 16% higher with bakers' YE. This could be related to the higher nitrogen content of the bakers' YE used in this study. Modification by UF of the YE had no significant influence on the growth of 4 of the 9 LAB strains. The three strains ofLactobacillus caseiwere negatively influenced by UF, as they did not grow as well in the media containing the YEF obtained after filtering with 1 and 3 kDa membranes. On a total solids basis, the 2.5× retentates from the 10 kDa membrane gave, on average, 4% lower &mgr;maxand 5% lower ODmaxvalues as compared to cultures where the corresponding YEF was used as medium supplement. This could also be partially related to the different nitrogen contents of the filtrates and retentates.Key words:Lactococcus, Pediococcus, Lactobacillus, amino acids

ISSN:0008-4166    

DOI:10.1139/w99-089

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Strain mX was isolated from a petrol-contaminated soil, after enrichment on minimal medium with 0.5% (v/v)meta-xylene as a sole carbon source. The strain was tentatively characterized asPseudomonas putidaand harboured a large plasmid (pMX) containingxylgenes involved in toluene ormeta-xylene degradation pathways via an alkyl monooxygenase and a catechol 2,3-dioxygenase. This new TOL-like plasmid was stable over two hundred generations and was self-transferable. After conjugal transfer toP. putidaF1, which possesses the Tod chromosomal toluene biodegradative pathway, the transconjugantP. putidaF1(pMX) was able to grow on benzene, toluene,meta-xylene, para-xylene, and ethylbenzene compounds as the sole carbon sources. Catechol 2,3-dioxygenases of the transconjugant cells presented a more relaxed substrate specificity than those of parental cells (strain mX andP. putidaF1).Key words: biodegradation, conjugative transfer, toluene, xylene,Pseudomonas.

ISSN:0008-4166    

DOI:10.1139/w99-093

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Thiomicrospirastrain CVO andArcobacterstrain FWKO B are two nitrate-reducing, sulfide-oxidizing bacteria (NR-SOB) isolated from the Coleville field in western Canada. Analysis by reverse sample genome probing (RSGP) indicates that both can be enriched from Coleville produced water samples by addition of nitrate. Neither could be enriched from waters produced from oil fields with a high resident temperature (40-60°C). In co-cultures of the two microorganisms, CVO dominated at lower and FWKO B at higher sulfide concentrations. Sulfide concentrations of up to 15 mM (480 ppm) could be controlled (i.e., reduced to lower values) by the co-culture. Mixed cultures of a sulfate-reducing bacterium (Desulfovibriostrain Lac6) and CVO or FWKO B produced considerably less sulfide than cultures of Lac6 alone, indicating that these NR-SOB can efficiently oxidize sulfide generated by sulfate reduction provided nitrate is present. The same observations were made for mixed cultures of a sulfur-oxidizing bacterium (Desulfuromonas acetoxidans) and CVO. The results indicate that successful nitrate-mediated conversion of sulfide to oxidized forms (sulfur, sulfate) in oil field production waters by NR-SOB requires the absence of high concentrations of electron donors (e.g., lactate, acetate) that can reverse the nitrate-mediated oxidation reaction

ISSN:0008-4166    

DOI:10.1139/w99-096

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The Canadian forest products industry suffers considerable losses due to discoloration caused by sapstain fungi. Although studied for a number of years, the identity, biology, and ecology of these fungi are still only partly understood. To determine which fungi caused stain problems, a detailed survey was conducted at seven selected sawmills across Canada. In summer 1997, fresh logs and lumber were set aside in the mills 1 month prior to sampling for fungi. We excluded bark-beetle-attacked wood and our logs remained free from their attack during storage. Five commercially important softwood species,Abies balsamea(L.) Mill.,Picea mariana(Mill.) B.S.P., Picea glauca(Moench) Voss, Pinus contortaDougl., andPinus banksianaLamb., were included in the studies. A total of 1863 isolates were isolated from stained and adjacent areas on test wood, and were identified based on their morphological and physiological characteristics and mating compatibility to 13 different species representing five genera. The most commonly encountered genus,Ophiostoma(97%), was represented by nine species. A more diverse range of fungi was found in logs than in lumber; some species were more frequently isolated from one type of substrate and rarely (or not at all) from the other. No fungal species occurred exclusively in a particular region or wood substrate.Key words: bluestain, lumber, logs,Ophiostoma,Ceratocystis.

ISSN:0008-4166    

DOI:10.1139/w99-090

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The importance of root and spore surface molecules in the interactions ofFusariumspp. with conifer roots, and cellular localization of proteins presumed to be involved in host defence, were investigated. For adhesion studies, using a combination of fluorescein isothiocyanate (FITC) labelled lectins and high perfomance liquid chromatography (HPLC), several sugars (pinitol, xylitol, galactose, mannose, and glucose) were detected in root surface mucilage. Both artificial substrata and detached living roots were used to evaluate the significance of selective removal of root or spore surface components on the adhesion process. The spores or roots were pretreated with either periodic acid, pronase E, potassium hydroxide or diethyl ether. Pretreatment of the spores with diethyl ether reduced significantly the level of spore adhesion, which suggests that the adhesive component is either a lipid, or is bound to lipid. Since oxidation of carbohydrate reactive sites with periodic acid on the root surface almost completely abolished the development of germ tubes by adherent spores, it was presumed that some of these periodate-sensitive substances serve as a nutrient source for the fungus. On inoculated roots,F. avenaceumandF. culmorumwere significantly pathogenic to both Norway spruce and Scots pine seedlings. Cytochemical labelling of sites of accumulation of host defence molecules within infected root tissues using anti-peroxidase demonstrated increased peroxidase activity in host cell walls. With anti-chitinase and anti-glucanase, gold labelling was found mainly on pathogen hyphal walls.Key words: conifer seedlings, adhesion,Fusariumspp., PR proteins, immunolocalization, lectins.

ISSN:0008-4166    

DOI:10.1139/w99-099

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The surface properties of aerial conidia (AC) from 24 strains of entomopathogenic fungi were studied and compared using the salt-mediated aggregation and sedimentation (SAS) assay, electron microscopy, FITC-labelled lectins, and spore dimensions. Spores with rugose surfaces were hydrophobic, whereas hydrophilic spores had smooth surfaces. Correlation analysis found no link between spore dimensions and either hydrophobicity or surface carbohydrates. However, there was a strong positive correlation between spore hydrophobicity and surface carbohydrates. The three spore types ofBeauveriabassianawere all shown to possess discrete surface hydrophobicities, which were also strongly linked to surface carbohydrate profiles. Various chemical treatments had pronounced effects on spore surface properties, with sodium dodecyl sulfate (SDS) and formic acid (FA) reducing both lectin binding and surface hydrophobicity. When FA-protein extracts were separated and analysed using SDS-PAGE, only the hydrophobic spores had low molecular weight hydrophobin-like peptides that were unglycosylated and contained disulfide bonds. The strains with hydrophilic AC had much lower levels of FA-extractable protein per spore dry weight compared to their more hydrophobic counterparts. Moreover, extracts of the more hydrophobic spores tended to have greater protein:carbohydrate ratios.Key words: fungi, spores, hydrophobicity, lectins, morphology, microbial insecticides, protein.

ISSN:0008-4166    

DOI:10.1139/w99-097

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The literature on sequencing as a tool for yeast molecular taxonomy is reviewed. Ribosomal DNA has been preferred for sequencing over other molecules such as mitochondrial DNA, and a large database is now available. rDNA consists of regions that evolve at different rates, allowing comparison of different levels of relationship among yeasts. Sequences of the 18S rDNA and the 25S rDNA have been largely used for yeast systematics and phylogeny, but the search for regions with increased resolving power has led to the study of the spacer regions of the rDNA. Few studies are concerned with signature sequences.Key words: yeast, molecular taxonomy, rDNA, sequencing.

ISSN:0008-4166    

DOI:10.1139/w99-094

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Arginine biosynthetic genes fromCampylobacter jejuniTGH9011 were cloned by functional complementation of the respectiveEscherichia coliarginine biosynthetic mutants. Complementation ofargA,argB,argC,argD,argE,argF, andargHauxotrophs was accomplished using a pBR322-basedC. jejuniTGH9011 plasmid library. By cross-complementation analyses, the first four steps of arginine biosynthesis were shown to be closely linked on the genome. Two additional clones complementing the first (ArgA) and fifth (ArgE) steps in arginine biosynthesis were obtained. Neither recombinant showed linkage to theargcluster, to each other, nor to other arginine biosynthetic functions by cross-complementation. GenesargFandargHwere not linked to other arginine biosynthetic genes by cross-complementation analysis. Restriction enzyme patterns of recombinant plasmids fell into five groups. Group I contained thearg(ABCD) complementing locus. Group II and Group III were the two genetic loci corresponding to theargAandargEcomplementing genes. Group II contains thehipOgene encodingN-benzoylglycine-amino-acid amidohydrolase, also known as hippurate hydrolase. Group III contains thehipOhomolog ofC. jejuni. Group IV represents theargFgene. GroupV is theargHgene. Functional complementation of mutations in the first four steps of the arginine biosynthetic pathway was obtained on recombinant plasmid pARGC2. The predicted order of gene complementation wasargCargA(argBargD). The sequence of the insert in plasmid pARGC2 revealed direct homologs forargC,argB, andargD. However, sequence analysis of the gene complementing ArgA function in two separateE. coliargAmutants determined that theC. jejunigene was not a canonicalargAgene. The gene complementing theargAdefect, which we callargO, showed limited homology to the streptothricin acetyltransferase gene (sat) ofEscherichia coli. The flanking open reading frames in pARGC2 showed no homologies to arginine biosynthetic genes. The structure of theargCOBDgene arrangement is discussed with reference to the presence and location of other arginine biosynthetic genes on the genome ofC. jejuniand other bacterial organisms.Key words: arginine synthesis,Campylobacter jejuni, arginine biosynthetic genes, gene sequence, gene arrangement.

ISSN:0008-4166    

DOI:10.1139/w99-095

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A xylanase gene (xynC) isolated from the anaerobic ruminal fungusNeocallimastixpatriciarumwas characterized. The gene consists of an N-terminal catalytic domain that exhibited homology to family 11 of glycosyl hydrolases, a C-terminal cellulose binding domain (CBD) and a putative dockerin domain in between. Each domain was linked by a short linker domain rich in proline and alanine. Deletion analysis demonstrated that the CBD was essential for optimal xylanase activity of the enzyme, while the putative dockerin domain may not be required for enzyme function.Key words: xylanase, cellulose binding domain,Neocallimastix patriciarum.

ISSN:0008-4166    

DOI:10.1139/w99-092

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Helicobacter pylorican colonize the human stomach for prolonged periods of time, and this colonization uniformly leads to the development of chronic active gastritis. In a small percentage of individuals, gastric pathology progresses to peptic ulceration or more rarely certain gastric cancers. In addition to non-specific inflammation, specific systemic and local immunity develops in response to gastric colonization by this pathogen. However, these responses combined appear inadequate for eliminatingH. pylorifrom the gastric mucosa. This is also the case in a mouse model of gastric colonization byH. pylori. In the present study, we attempted to determine whether the mammalian host response to infection withH. pyloriexerts any overt antibacterial effects. To this end we examinedH. pyloricolonization in normal mice, and mice immunosuppressed by treatment with a corticosteroid. Despite obvious suppression of the immune response in the latter mice,H. pyloriburdens remained similar in both groups after three months of colonization. This suggests that the murine host response, at least, exerts little obvious protection againstH. pyloricolonization.Key words:Helicobacter pylori, immunosuppression, mice.

ISSN:0008-4166    

DOI:10.1139/w99-101

出版商:NRC Research Press    

年代:1999

数据来源: NRC