摘要:

In our studies on keratinophilic fungi in Spain, an arthroconidial anamorphic species has been recovered and is herein described as new.Arthrographis albasp.nov. is characterized by having arthroconidia borne from laterally or pseudodichotomously branched conidiophores, white colonies, and nil or restricted growth at 37 °C. Analysis of restriction fragment length polymorphisms of ribosomal DNA reveals differences withArthrographis kalrae, a morphologically similar species.Key words:Arthrographis alba, Hyphomycetes, rDNA.

ISSN:0008-4166    

DOI:10.1139/m96-152

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Hybrid yeast strains were constructed using haploidSaccharomyces cerevisiaeandSaccharomyces cerevisiaevar.diastaticusstrains to get haploid meiotic recombinants having more than one copy ofSTA1,STA2, andSTA3genes.STAgenes were localized on the chromosomes by pulsed field gel electrophoresis. Working gene dosage effects were found amongSTAgenes in liquid starch medium, indicating low levels of glucose repression. Growth of strains, however, was not influenced by theirSTAcopy number.Key words: yeast,STAgenes, gene dosage, karyotyping.

ISSN:0008-4166    

DOI:10.1139/m96-153

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Pentachlorophenol (PCP) caused a rapid and pronounced increase in the rate of biosynthesis of the superoxide dismutase (SOD) in fungal strainHumicola lutea110. Mn-containing SOD (Mn-SOD) was mainly responsible for modulating total cell SOD. The kinetics of SOD synthesis in the presence of PCP demonstrated the induction model of enzyme formation. This model was also supported by deinduction experiments, because the removal of the PCP was followed by a marked decrease in SOD activity. PCP also caused a moderate induction of catalase. The concentrations, which were effective in inducing the Mn-SOD, increased the cyanide-resistant respiration. It seems likely that PCP increased the rate of intracellular production of superoxide. Addition of inhibitors of transcription and translation to cultures in the presence of inducer (PCP) inhibited further accumulation of SOD activity. These data suggest that PCP, probably by the increase ofcontent, accelerates new enzyme synthesis in fungal strainHumicola lutea110.Key words: superoxide dismutase, superoxide, induction, pentachlorophenol, fungi,Humicola lutea.

ISSN:0008-4166    

DOI:10.1139/m96-154

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The anaerobic degradative pathway for metabolism of 2,4,6-trinitrotoluene (TNT) by a consortium ofDesulfovibriospp. isolated from a creek sediment was studied. This consortium has the metabolic capability to degrade TNT to fatty acids. The growth of the consortium and the metabolism of TNT were greatly enhanced in the presence of an additional carbon source like pyruvate. The optimal concentration of pyruvate for the maximum rate of TNT degradation was 15–20 mM. Various intermediates of TNT metabolism were identified. The first step in the pathway was reduction of TNT to 4-amino-2,6-dinitrotoluene and 2-amino-4,6-dinitrotoluene, which were further reduced to 2,4-diamino,6-nitrotoluene. The next intermediate to appear in the culture medium was nitrobenzoic acid, followed by cyclohexanone, 2-methyl pentanoic acid, butyric acid, and acetic acid. A study using radiolabeled TNT showed that no CO2was produced from TNT during metabolism. The mass balance of the radiolabeled study showed that 49.6% of the TNT was converted to acetic acid, 28% was assimilated into biomass as trichloroacetic acid precipitable materials, and the rest was distributed as various TNT intermediates. MostDesulfovibriospp. are incomplete oxidizers that are unable to carry out the terminal oxidation of organic substrates. The major end product of TNT metabolism was acetic acid. The bacteria grew on all the TNT intermediates tested as sole source of carbon, except on acetic acid, confirming that theDesulfovibriospp. have the enzymes necessary for complete degradation of TNT to acetate.Key words: TNT, bioremediation, sulfate reducers, anaerobic process, butyric acid,Desulfovibrio, spp.

ISSN:0008-4166    

DOI:10.1139/m96-155

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

To determine the taxonomic relationship between Thai soybean bradyrhizobia and soybean bradyrhizobia from other regions, a total of 62Bradyrhizobiumstrains were isolated in Thailand. The genetic diversity of the strains was examined with reference to 46 Japanese and 15 USDA strains. The degree of sequence divergence in and around commonnodgene regions of the 123 strains was estimated by restriction fragment length polymorphism analysis using theBradyrhizobium japonicumUSDA 110 commonnodDYABCgene probe. The phylogenetic grouping of the strains resulted in four major clusters. Cluster 1 comprised the Japanese and USDA strains, which originated in temperate regions, whereas clusters 3 and 4 comprised the tropical Thai strains. Cluster 1 strains comprised the DNA homology groups I and Ia, and hence, were classified asB.japonicum. Cluster 2 strains were in the DNA homology group II, and hence, were classified asBradyrhizobium elkanii. Clusters 3 and 4 strains, however, did not correspond to any known DNA homology groups. These results indicate that Thai soybean bradyrhizobia are distantly related toB.japonicumandB.elkanii.Key words:Bradyrhizobium japonicum,Bradyrhizobium elkanii, commonnodgene, RFLP, genetic diversity.

ISSN:0008-4166    

DOI:10.1139/m96-156

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

The gram-negative anaerobeOxalobacter formigenes, grows on oxalate as the principal carbon and energy source, but a small amount of acetate is also required for growth. Experiments were conducted to determine the distribution and the position of label in cellular amino acids from cells grown on [13C]oxalate, [13C]acetate (1-13C, 2-13C, and U-13C), and13CCO3. The labeling pattern (determined with NMR spectroscopy) of amino acids was consistent with their formation through common biosynthetic pathways. The majority of the carbons in the amino acids that are usually derived from pyruvate, oxaloacetate, α-ketoglutarate, 3-phosphoglycerate, and carbon in the aromatic amino acids were labeled by oxalate. Carbon from13CO3was assimilated primarily into amino acids expected to be derived from oxaloacetate and α-ketoglutarate. Approximately 60% of the acetate that was assimilated into amino acids was incorporated as a C2unit into proline, arginine, glutamate, and leucine. The pattern of labeling from acetate in glutamate, arginine, and proline was consistent with acetate incorporation via citrate (si)-synthase and subsequent formation of α-ketoglutarate via the first third of the tricarboxylic acid pathway. Acetate was also assimilated into amino acids derived from pyruvate and oxaloacetate, but results indicated that this incorporation was as single carbon atoms. Based on these findings, cell-free extracts were assayed for several key biosynthetic enzymes. Enzymatic activities found included glutamate dehydrogenase, phosphoenolpyruvate carboxylase, and pyruvate carboxylase. These findings are consistent with proposed biosynthetic mechanisms.Key words: oxalate, carbon flow, carbon assimilation.

ISSN:0008-4166    

DOI:10.1139/m96-157

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Acinetobacter calcoaceticusS30 could grow (doubling time, 7 h) on octacosane (C28) and degraded about 70% of the substrate during growth. Octacosanol, octacosanoic acid, and other lower carboxylic acids were identified during degradation of octacosane.Acinetobacter calcoaceticusS30 could also grow on intermediate metabolites, namely octacosanol and octacosanoic acid, although the doubling time was greater on octacosanoic acid (72 h on octacosanol and 120 h on octacosanoic acid). Whole cells ofA.calcoaceticusS30 using [18-14C]octacosane mineralized 65% of the octacosane to14CO2and 30% of the radiolabel was retained in the cell biomass in 24 h.Acinetobacter calcoaceticusS30 converts octacosane to octacosanol through an oxidation step, which is then oxidized to octacosanoic acid and then β-oxidized to CO2. Among several metabolic inhibitors, those of the sulphydryl group greatly inhibited the uptake of octacosanol and octacosanoic acid at much lower concentrations. The electron transport inhibitors were potent inhibitors of octacosane, octacosanol, and octacosanoic acid uptake, suggesting that the oxidation of these substrates is an energy-dependent process.Key words:Acinetobacter calcoaceticus, mineralization, octacosane, octacosanol, octacosanoic acid.

ISSN:0008-4166    

DOI:10.1139/m96-158

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Nuclear rDNA from 120 isolates of 34Fusariumspp. andMicrodochium nivalewas compared by restriction fragment length polymorphism (RFLP) analysis after polymerase chain reaction amplification. The RFLPs allowed differentiation between species or groups of species. The presence or absence of each of 75 DNA bands was also used to compile a similarity matrix for cluster analysis to show estimated phylogenetic relationships. There was mostly little diversity between isolates of the same species. However, there were at least two distinct genetic types among isolates that conformed morphologically to each of the speciesF.avenaceum,F.sambucinum,F.flocciferum, andF.proliferatum. Most relationships were consistent with current understanding ofFusariumtaxonomy. The division into taxonomic sections based on morphological characteristics was generally not supported.Key words:Fusarium, rDNA, phylogeny.

ISSN:0008-4166    

DOI:10.1139/m96-159

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

Isocitrate dehydrogenase is considered to be one of the key regulatory enzymes in the conversion of glucose into fatty acids by oleaginous microorganisms. A dual coenzyme-specific isocitrate dehydrogenase (EC 1.1.1.41) (IDH) was isolated from the primitive fungusPythium ultimumand purified by 211-fold by sequential ion-exchange, affinity, and gel filtration chromatographies. Specific activity of the partially purified enzyme was 76.2 μmol/(min∙mg protein) with NAD+and 40% less active with NADP+. Optimum pH for activity was 8.5–9.5.Kmvalues forthreo-D-isocitrate and NAD+were 0.031 and 0.55 mM, respectively. The estimated molecular mass of the IDH was 96 kDa under nondenaturing conditions and 48 kDa under denaturing conditions, suggesting that the enzyme is composed of two subunits of the same size. The enzyme was relatively stable up to 55 °C, but no activity was detected after exposure to 65 °C for 15 min. Mg2+or Mn2+were required for activity.Key words: isocitric dehydrogenase,Pythium ultimum, dual cofactor specific, oleaginicit

ISSN:0008-4166    

DOI:10.1139/m96-160

出版商:NRC Research Press    

年代:1996

数据来源: NRC

摘要:

A pair of oligonucleotide primers were designed from the nucleotide sequence of the gene encoding the small subunit ribosomal RNA (SrRNA) of the oral protozoan parasiteEntamoeba gingivalis. The primers amplified a 1.4-kb DNA fragment by polymerase chain reaction and were specific forEntamoeba gingivalisbut not for other protozoa, oral protists and bacteria, or human leukocytes. With this method, the DNA from as few as 30 cells ofEntamoeba gingivaliscould be detected. These results suggest that this approach is applicable to the detection and identification ofEntamoeba gingivalisin the human oral cavity.Key words:Entamoeba gingivalis, small subunit rRNA, polymerase chain reaction, diagnostics.

ISSN:0008-4166    

DOI:10.1139/m96-161

出版商:NRC Research Press    

年代:1996

数据来源: NRC