摘要:

To elucidate the phylogenetic relationships between Thai soybean bradyrhizobia and USDA strains ofBradyrhizobium, restriction fragment length polymorphism (RFLP) analysis using thenifDKgene probe and sequencing of the partial 16S rRNA gene were performed. In our previous work, Thai isolates ofBradyrhizobiumsp. (Glycine max) were separated clearly fromBradyrhizobium japonicumandBradyrhizobium elkaniibased on the RFLP analysis using thenodDYABCgene probe. RFLP analysis using thenifDKgene probe divided 14 Thai isolates and eight USDA strains ofB.japonicuminto different groups, respectively, but categorized into the same cluster. All of seven strains within these Thai isolates had the same sequence of the partial 16S rRNA gene, and it was an intermediate sequence between those ofB.japonicumUSDA 110 andB.elkaniiUSDA 76T. Furthermore, three USDA strains ofB.japonicum, USDA 6 (B.japonicumATCC 10324T), USDA 115 and USDA 129, had the same partial 16S rRNA gene sequence that seven Thai isolates had. These results suggest that Thai isolates ofBradyrhizobiumsp. (Glycine max) are genetically distinct from USDA strains ofB.japonicumandB.elkanii, but also indicate a close relationship between Thai isolates and USDA strains ofB.japonicum.Key words:Bradyrhizobium, 16S rRNA gene,nifgene, soybean, Thailand.

ISSN:0008-4166    

DOI:10.1139/w99-061

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The nucleotide sequence of a region downstream of theListeria monocytogenesflagellin gene,flaA, revealed two putative chemotaxis genes,cheYandcheA. These genes have been shown to be transcribed as a bicistronic unit. In this study Tn916&Dgr;Emutagenesis was used to generate two mutants, PF10 and PF16, which contain transposon inserts in the promoter region of this operon. These mutants were motile in liquid, but had reduced flagellin expression and were unable to burrow or swarm on soft agar plates. Complementation of the single transposon-copy mutant PF16 with clonedcheYandcheAin trans partially restored microaerotaxis and swarming on soft agar. The complemented strain did not exhibit any increase in flagellin production. Both PF10 and PF16 appear deficient in their ability to attach to the mouse fibroblast cell line 3T3.Key words:Listeria, motility, flagella, chemotaxis.

ISSN:0008-4166    

DOI:10.1139/w99-052

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A monokaryotic strain of the white-rot fungusPycnoporus cinnabarinuswas shown to produce, in a 2-L bioreactor culture, 100 mg·L-1benzaldehyde (bitter almond aroma) fromL-phenylalanine with a productivity of 33 mg·L-1·day-1. The addition of HP20 resin, a styrene divinylbenzene copolymer highly selective for benzaldehyde, enabled an eightfold increase in the production of benzaldehyde and a twofold increase in productivity. In the presence of HP20 resin, the production of 790 mg·L-1benzaldehyde was concomitant with the synthesis of cinnamic acid derivatives of high organoleptic notes such as cinnamaldehyde, cinnamyl alcohol, and methyl cinnamate.Key words: benzaldehyde,L-phenylalanine,Pycnoporus cinnabarinus, adsorbents.

ISSN:0008-4166    

DOI:10.1139/w99-056

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Macrophages recognize, adhere to, and phagocytoseSalmonella typhimurium. The major outer membrane protein OmpC is a candidate ligand for macrophage recognition. To confirm this we used transposon mutagenesis to develop anompC-deficient mutant in a known virulent strain ofS. typhimurium; mutant and wild type were compared in macrophage adherence and association assays. Radiolabeled wild typeS. typhimuriumbound to macrophages at five-fold higher levels than did theompCmutant. In association assays, macrophages in monolayers bound and internalized three-fold more wild type than mutant, while macrophages in suspension bound and internalized 40-fold more wild type than mutant. TheompCgene of our test strain ofS. typhimuriumcontains several discrete differences compared with theompCgenes ofSalmonella typhiandEscherichia coli. The deduced OmpC amino acid sequence ofS. typhimuriumshares 77 and 98% identity with OmpC amino acid sequences ofE. coliandS. typhi, respectively. Evidence from this study supports a role for the OmpC protein in initial recognition by macrophages and distinguishes regions of this protein that potentially participate in host-cell recognition of bacteria by phagocytic cells.Key words: Salmonella, porin, macrophage, outer membrane protein, DNA sequencing.

ISSN:0008-4166    

DOI:10.1139/w99-053

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Fourteen monoclonal antibodies (Mabs) were isolated that react with surface antigens ofPediococcusbeer spoilage organisms, includingP. damnosus,P. pentosaceous,P. acidilactici, and unspeciated isolates. Immunoblotting, enzyme immunoassays (EIAs) of protease- and neuraminidase-treated surface antigen extracts, carbohydrate competition EIAs, and cardiolipin EIAs were used to characterize the bacterial antigens involved in Mab binding. Antigen stability in situ was tested by protease treatment or surface antigen extraction of washed bacteria. In most cases, the Mabs bind toPediococcussurface antigens that appear to be covalently bound cell wall polymers resistant to alteration or removal from the bacterial surface. These bacterial surface antigen reactive Mabs show good potential for rapid, sensitive, and specific immunoassay detection ofPediococcusbeer spoilage organisms.Key words: beer spoilage organism, immunoassay, monoclonal antibodies,Pediococcus, surface antigens.

ISSN:0008-4166    

DOI:10.1139/w99-060

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The GUS marker gene system has been developed for the study of bacterial ecology, particularly rhizobial competition. For high-throughput field screening of rhizobial competition, the technique must be robust and reliable under diverse conditions, with diverse cultivars and strains. Here we demonstrate its applicability to the evaluation of competition on five differentPhaseolus vulgariscultivars with 10 differentRhizobiumstrains. We describe refinements of the GUS assay, which make it more affordable and applicable to field-based studies, and use the assay to examine the effect of sample size on the accuracy of nodule occupancy measurements.Key words: GUS gene,Rhizobium, rhizobial competition, microbial ecology.

ISSN:0008-4166    

DOI:10.1139/w99-064

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A morphological and physiological description of an anamorphic basidiomycetous yeast species, namedTrichosporon guehoae(CBS 8521T), is presented. The ability to assimilate several aliphatic and aromatic compounds as sole source of carbon and energy is reported. The phylogenetic position within the genus, based on nuclear base sequencing of the D1/D2 region of the large subunit of rDNA is discussed.Key words: basidiomycetes, taxonomy,Trichosporon guehoaesp.nov., yeasts.

ISSN:0008-4166    

DOI:10.1139/w99-055

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

In this study, urine was collected from groups of volunteers following the consumption of water, ascorbic acid, or cranberry supplements. Only ascorbic acid intake consistently produced acidic urine. Photospectroscopy data indicated that increased water consumption produced urine with lower protein content. Surface tension measurements of the collected urine showed that both water and cranberry supplementation consistently produced urine with surface tensions higher than the control or urine collected following ascorbic acid intake. These urine samples were also employed to study uropathogen adhesion to silicone rubber in a parallel plate flow chamber. Urine obtained after ascorbic acid or cranberry supplementation reduced the initial deposition rates and numbers of adherentEscherichia coliandEnterococcus faecalis, but notPseudomonas aeruginosa, Staphylococcus epidermidis,orCandida albicans.Conversely, urine obtained from subjects with increased water intake vastly increased the initial deposition rates and numbers of adherentE. coliandE. faecalis(P< 0.05).Key words: adhesion, human urine, natural products, silicone rubber, uropathogens.

ISSN:0008-4166    

DOI:10.1139/w99-065

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The yeastsSaccharomyces cerevisiae,Candida boidinii,Pichia angusta, andPichia anomalawere tested for glycerol production both under osmotic stress and by addition of a sulfite-steering agent. The osmotic pressure was increased by employing glucose concentrations from 50 to 200 g/L and by supplementing with NaCl (40 g/L). Of all the yeasts,S. cerevisiaeexhibited the highest level of osmotolerance. The increased osmotic pressure affected glycerol formation the most inC. boidinii. In bothPichiaspecies, glycerol formation was not sufficiently induced when exposed to sugar and salt stress. The addition of 40 g/L Na2SO3to the medium containing 100 g/L glucose shifted the metabolism of all yeasts towards glycerol formation.Saccharomyces cerevisiaeachieved 68.6%, whileC. boidiniireached 25.5% of the theoretical glycerol yield, respectively. The highest glycerol yield, 82.3% of the theoretical, was produced byS. cerevisiaeunder microaerophilic conditions.Key words: glycerol, osmotolerant yeast, sulfite-tolerant yeast,Saccharomyces cerevisiae,Candida boidinii.

ISSN:0008-4166    

DOI:10.1139/w99-054

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The physiological criteria for the development of crude oil emulsifying activity in aRhodococcusspecies isolated from sea water was investigated. The bacterium was used as a model organism and all experiments were performed in shake flasks at 30°C. The development of emulsifying activity was inducible, but only under conditions of cell growth. A test was developed for assessing the ability of different chemical compounds to induce the crude oil emulsifying activity in acetate pre-grown cells, and a comprehensive survey of possible inducers carried out. The compounds that gave excellent or good emulsification in the test assay includedn-alkanes (C11to C18), pristane, 1-decene, fatty alcohols (C14to C18), the fatty aldehydes decanal and dodecanal, some unsaturated fatty acids and some oils containing glycerol esters of unsaturated fatty acids. All these compounds also served as sole carbon and energy sources. Alkanes and fatty acids behaving as solids at 30°C did not function as inducers in the assay. Heptamethylnonane served as a moderate inducer, but not as a growth substrate. The inducers had to be present in the concentration range of 0.01 to 0.05% (w/v) in order to give a detectable emulsion under the conditions of the assay. The development of the emulsifying activity, hypothesised to comprise compounds from the hydrophobic cell surface, is suggested to be coordinated with new cell wall synthesis.Key words: emulsification, crude oil, inducers, alkane-oxidation, bacteri

ISSN:0008-4166    

DOI:10.1139/w99-057

出版商:NRC Research Press    

年代:1999

数据来源: NRC