摘要:

Numerous ultrastructural and biochemical analyses have been performed to characterize the cell wall composition and structure ofCandida albicans. However, little investigation has focused on how subtle differences in cell wall structure influence the intracellular transport of amino acids and monosaccharides. In this studyC. albicans4918 and ATCC 10231 were grown in culture conditions capable of modifying surface mannoproteins and induced surface hydrophobic or hydrophilic yeast cell wall states. Subcultures of these hydrophobic and hydrophilic yeasts were subsequently incubated with one of seven L-[3H] amino acids: glycine, leucine, proline, serine, aspartic acid, lysine, or arginine. The transport of [3H] mannose and [3H] N-acetyl-D-glucosamine were also investigated. This study revealed significant strain differences (P0.05) between hydrophilic and hydrophobic yeast transport of these nutrients throughout a 2 h incubation. Hydrophilic cultures of 4918 and ATCC 10231 transported nearly two times more (pmol mg-1dry weight) proline, mannose, and N-acetyl-D-glucosamine than hydrophobic yeast. Hydrophobic cultures preferentially incorporated serine and aspartic acid in both these strains. Strain variation was indicated with the transport of leucine, lysine, and arginine, as follows: experiments showed that hydrophilic 4918 cultures selectively transported leucine, lysine, and arginine, whereas, the hydrophobic ATCC 10231 cultures incorporated these amino acids.Key words:Candida albicans, mannoproteins, amino acid transport.

ISSN:0008-4166    

DOI:10.1139/w99-035

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Previous studies showed that benzothiophene and 3- and 5-methylbenzothiophenes are oxidized by some bacteria to yield their corresponding sulfones, which were not subsequently degraded. In this study, a filamentous bacterium was isolated, which grew on each of these three sulfones as its sole carbon, sulfur, and energy source. Based on 16S rRNA gene sequencing and scanning electron microscopy, the isolate was found to belong to the genusPseudonocardiaand assigned the strain designation DB1. Benzothiophene sulfone and 3-methylbenzothiophene sulfone were more readily biodegraded than 5-methylbenzothiophene sulfone, and growth on these three compounds resulted in the release of 57, 62, and 28% of the substrate carbon as CO2, respectively. The thiophene ring was also cleaved, and between 44 and 88% of the sulfur from the consumed substrate was found as sulfate and (or) sulfite. Strain DB1 grew on benzoate, dibenzothiophene sulfone, and hexadecanoic acid, but it could not grow on benzofuran, dibenzothiophene, dibenzothiophene sulfoxide, hexadecane, indole, naphthalene, phenol, 2-sulfobenzoic acid, sulfolane, benzothiophene, or 3- or 5-methylbenzothiophenes. In addition, it did not oxidize the latter three compounds to their sulfones.Key words: benzothiophene sulfone, biodegradation, mineralization, sulfur heterocycles,Pseudonocardia.

ISSN:0008-4166    

DOI:10.1139/w99-019

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Mycobacteriumstrain S1, originally described asRhodococcusstrain S1 by chemotaxonomic criteria, was isolated by growth on anthracene, and is unable to use any of nine other polycyclic aromatic compounds as carbon source. Metabolism of phenanthrene during growth on anthracene as sole carbon source results in the accumulation of traces of a dihydrodiol metabolite in the growth medium, which, by comparison with authentic standards, has been tentatively identified as phenanthrenetrans-9,10-dihydrodiol. Anthracene metabolites were ruled out on the basis of comparisons with authentic anthracene dihydrodiols fromPseudomonas fluorescensD1 and chemically synthesized anthrols. The original source of phenanthrene for dihydrodiol production was phenanthrene present as a <1% contaminant in the anthracene used as carbon source. However, addition of further phenanthrene to the anthracene growth medium increased the level of phenanthrenetrans-9,10-dihydrodiol formed.Mycobacteriumstrain S1 also produced phenanthrenetrans-9,10-dihydrodiol when grown in a glucose-salts medium in the presence of phenanthrene. This dihydrodiol is a dead-end metabolite, and neither it nor its parent hydrocarbon are able to support the growth ofMycobacteriumstrain S1. Studies with metyrapone and ancimidol, which did not inhibit growth on anthracene but did inhibit formation of phenanthrenetrans-9,10-dihydrodiol, suggest it is likely the product of a cytochrome P450 monooxygenase-like activity.Key words: phenanthrenetrans-9,10-dihydrodiol,Mycobacterium.

ISSN:0008-4166    

DOI:10.1139/w99-017

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Diisopropanolamine (DIPA) is a "sweetening agent" used to remove hydrogen sulfide from sour natural gas, and it is a contaminant at some sour gas treatment facilities in western Canada. To investigate the biodegradation of this alkanolamine,14C-DIPA was used in anaerobic and aerobic mineralization studies. Between 3 and 78% of the radioactivity from this compound was released as14CO2in sediment-enrichment cultures incubated under nitrate-reducing conditions. Similarly, 12-78% of the label was converted to14CO2in sediment-enrichment cultures incubated under Mn(IV)-reducing conditions. These activities were observed at 8°C, a typical groundwater temperature in western Canada, and at 28°C. In contrast, DIPA-degrading activity was difficult to sustain under Fe(III)-reducing conditions, and <25% of the radioactive label from14C-DIPA was liberated as14CO2. Two mixed cultures and two isolates (both irregular, non-sporeforming, Gram-positive rods) were used to assess aerobic mineralization of14C-DIPA. The aerobic mixed cultures released 73 and 79% of the radioactive label as14CO2, whereas the pure cultures liberated only 39 and 47% as14CO2. Between one-third and one-half of the nitrogen from DIPA was found as ammonium-N in aerobic batch cultures. These results clearly demonstrate that DIPA is mineralized under a variety of incubation conditions.Key words: alkanolamine, biodegradation, diisopropanolamine, mineralization, natural ga

ISSN:0008-4166    

DOI:10.1139/w99-016

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Rhizoctonia solanianastomosis group (AG) 11 causes serious damping-off and hypocotyl rot of lupins (Lupinus angustifoliusL.) and is wide-spread in the northern grain-belt of Western Australia. We compared growth of AG-11 to AG-8, which causes bare-patch of grain crops including lupin. AG-11 grew significantly faster than AG-8 on potato dextrose agar (PDA) at several temperatures (10, 15, 20, 25, or 30°C) and also grew best within the pH range of 4-7. Growth of AG-8 was best at pH 7. There was no difference in the linear growth in soil of both AGs at 10°C, but AG-11 grew at a significantly faster rate at 20°C. Reduction in growth of AG-11 on osmotically adjusted PDA at temperatures between 10 and 30°C was more pronounced than that of AG-8. AG-11 caused very little lupin pre-emergence damping-off and hypocotyl rot at 10°C, and most severe hypocotyl rot was recorded at 20 and 25°C. Severity of hypocotyl rot caused by AG-11 at soil water potentials of -0.1, -0.07, and -0.05 MPa was higher than at -0.03 MPa. It appears that AG-11 is well suited to the environmental conditions of the relatively small area in Western Australia from which it is readily isolated.Key words:Rhizoctonia solani, anastomosis groups, osmotic potential,

ISSN:0008-4166    

DOI:10.1139/w99-027

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Yersinia enterocolitica, an invasive foodborne human pathogen, degrades polypectate by producing two depolymerizing enzymes, pectate lyase (PL) and polygalacturonase (PG). The gene encoding the PG activity, designatedpehY, was located in a 3-kb genomic fragment ofY. enterocoliticaATCC 49397. The complete nucleotide sequence of this 3-kb fragment was determined and an open reading frame consisting of 1803 bp was predicted to encode a PG protein with an estimatedMrof 66 kDa and pI of 6.3. The amino acid sequence of prePG showed 59 and 43% identity to that of the exopolygalacturonase (exoPG) ofErwinia chrysanthemiandRalstonia solanacearum, respectively. TheY. enterocoliticaPG overproduced inEscherichia coliwas purified to near homogeneity using perfusion cation exchange chromatography. Analysis of the PG depolymerization products by high performance anion-exchange chromatography and pulsed amperometric detection (HPAEC-PAD) revealed the exolytic nature of this enzyme. TheY. enterocoliticaPL overproduced inE. coliwas also partially purified and theMrand pI were estimated to be 55 kDa and 5.2, respectively. HPAEC-PAD analysis of the PL depolymerization products indicated the endolytic nature of this enzyme. Southern hybridization analyses revealed thatpehYandpelgenes ofY. enterocoliticaare possibly encoded in the chromosome rather than in the plasmid. Purified exopolygalacturonase (over 10 activity units) was unable to macerate plant tissues.Key words: pectinase activities, human pathogen, HPLC analysis,pehYgene.

ISSN:0008-4166    

DOI:10.1139/w99-034

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Sphingomonassp. strain RW1 is able to mineralise dibenzofuran and dibenzo-p-dioxin. Three mutants were constructed that could not use dibenzofuran or dibenzo-p-dioxin as a carbon source but were able to grow with the succeeding metabolites of the pathway. Two different mutagenic agents were applied, a chemical treatment with 1-methyl-3-nitro-1-nitrosoguanidine, resulting in mutants RW1-N6 and RW1-N7, and a biological insertion mutagenesis with the mini-Tn5transposon pBSL118, resulting in mutant RW1-M3. Southern blot analysis and PCR experiments confirmed a single insertion of the mini-Tn5into one of the genes coding for the oxygenase component of the dibenzofuran 4,4a-dioxygenase system. The genetic stability of these mutants was examined after growth with complex medium under nonselective conditions. All three mutants failed to revert to wild-type metabolic functions.Key words:Sphingomonas, mutation, stability, mini-Tn5, 1-methyl-3-nitro-1-nitrosoguanidine.

ISSN:0008-4166    

DOI:10.1139/w99-029

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Thirteen strains of chromoblastomycosis and phaeohyphomycosis etiologic agent fungi were obtained from different geographical origins. These strains were genotypically compared by means of the RAPD (Random Amplified Polymorphic DNA) technique. The data generated showed a high degree of polymorphism between distinct species and a low polymorphism between strains of the same species. The results generated by these tests were subjected to a numerical taxonomy analysis, using the unweighted pair-group method. A phenogram was constructed for the set of strains studied. Based on its structure, we concluded that genotypical data provide enough information to us to use the unweighted pair-group method to cluster the strains in accordance to their respective species. The phenogram grouped in a single branch the strains ofFonsecaea pedrosoiandF. compactaspecies, indicating a great similarity between these fungi, and suggesting that the classification as distinct species may not be appropriate for these species of the genusFonsecaea.Key words: chromoblastomycosis, phaeohyphomycosis, dematiaceous fungi, RAPD,Fonsecaea pedrosoi.

ISSN:0008-4166    

DOI:10.1139/w99-030

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Expression of theSUC2gene encoding invertase was studied using free and gelatin-immobilized yeast cells to try to explain the high activity of this enzyme exhibited by immobilized cells when allowed to grow in a nutrient medium. The results indicated that at least two factors are probably responsible for the accumulation of invertase in immobilized cells. First, the expression of theSUC2gene was maintained throughout growth in immobilized cells, whereas its expression was only transient in free cells. Second, invertase of immobilized cells was shown to be less susceptible to endogenous proteolytic attack than that of the corresponding free cells. These results have been interpreted, respectively, in terms of diffusional limitations and changes in the pattern of invertase glycosylation due to growth of yeast in an immobilized state.Key words: immobilization, invertase, yeast, proteases.

ISSN:0008-4166    

DOI:10.1139/w99-024

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

We have isolated a 2.5-kb DNA fragment from plasmid pST5R7 encoding a sucrose utilization system fromEscherichia coliB-62 which confers a sucrose-fermenting phenotype to transformedE. coliK-12 strains. DNA-sequence determination revealed one full-length open reading frame 98% identical tocscA, the sucrose-hydrolase (invertase) gene of thecscregulon fromE. coliEC3132. Functional characterization indicates that high-level expression and limited periplasmic release of invertase is responsible for the sucrose-fermenting capacity of transformedE. coliK-12 strains carryingcscA.Key words: sucrose utilization, sucrose hydrolase, invertase, recombinant protein production.

ISSN:0008-4166    

DOI:10.1139/w99-031

出版商:NRC Research Press    

年代:1999

数据来源: NRC