摘要:

The results of the present study show that whereas both BALB/c and C57BL/6 mice parenterally inoculated with a horse serum albumin -Escherichia coliO157 antigen conjugate vaccine develop systemic, specific antibodies to the carrier protein, only the former mice routinely develop antibodies to the carbohydrate O157 moiety. However, little convincing evidence was found to show that these antibodies transuded into the intestinal tract either naturally or in response to an oral inoculum of the pathogen. Moreover, this vaccination procedure failed to protect mice against intestinal colonization following oral challenge with the pathogen. Thus, the results of this study suggest that parenteral vaccination might be an unsuitable strategy for combattingE. coliO157:H7 organisms located in the gut.Key words:Escherichia coli, glycoconjugate vaccine, mice.

ISSN:0008-4166    

DOI:10.1139/w99-008

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Bacteria are known to rapidly produce new phenotypes, but it is unclear how phenotype "plasticity" relates to studies on the population ecology of bacteria in complex environments. We characterised a collection of 14 spontaneous phenotype variants, derived from in vitro and in vivo cultures (wheat roots) ofPseudomonas corrugata2140, using fatty acid methyl ester profiles (GC-FAME), carbon substrate utilisation (BIOLOG), and in vitro inhibition against seven soil microorganisms. All three phenotype profiles indicated marked differences between some variants and the parent isolate. Some variant types were classified taxonomically by GC-FAME as different species to their wild-type parent, and up to a Euclidian distance of 11 from their parent. Taxonomic identification by the BIOLOG assay was more consistent; however, use of 22 carbon sources were altered (lost or gained) in one or more variants. All variant types had a reduced ability to inhibit one or more test organisms, depending on the variant and test organism. Hierarchical cluster analysis of variants using GC-FAME, BIOLOG, and inhibition profiles produced different groupings. The ability of variants to cross taxonomic boundaries specified by the GC-FAME and BIOLOG libraries at the species level has implications for both taxonomy and the ecological study of bacterial communities.Key words:Pseudomonas corrugata, variants, phenotype plasticity, FAME, BIOLOG.

ISSN:0008-4166    

DOI:10.1139/w99-006

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A physical genome map of theMoraxella catarrhalistype strain (ATCC 25238) has been constructed using pulsed field gel electrophoresis. Macrorestriction analyses of the genome ofM. catarrhaliswere performed by digestion with the restriction enzymesSmaI,NotI, andRsrII, which cleave the single circular chromosome into 9, 10, and 6 fragments, respectively. The chromosomal fragments generated by pulsed field gel electrophoresis were converted to a linkage map utilizing a combination of partial digestions, and cross-hybridizations.Moraxella catarrhalis, like a number of other respiratory pathogens, has a relatively small genome estimated at 1750 kilobase pairs or about 40% of the size of theEscherichia coligenome. The locations of the four ribosomal RNA operons (rrnLS) were determined by Southern hybridization and by digestion with I-CeuI endonuclease. A number of genes involved in virulence have been placed onto the physical map by Southern hybridization including those encoding the predominant outer-membrane proteins and the chromosomal gene encoding beta-lactamase.Key words:Moraxella catarrhalis, physical map, genome analysis, pulsed-field gel electrophoresis, virulence.

ISSN:0008-4166    

DOI:10.1139/w99-005

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

In this study we have quantified the ionic content and volume of native aquatic, and two cultured bacteria, by X-ray microanalysis (XRMA) in the transmission electron microscope (TEM). The cellular concentrations of magnesium (means of 630 and 710 mM) were more than an order of a magnitude higher than the outside concentrations. The internal concentrations of sodium were on average 50-180 mM, and the [K+]/[Na+] ratios were in the range of 0.1-0.5; lowest for apparently nonactive bacteria. Magnesium and chloride probably act as the major components of cell turgor, since no other inorganic ions were present in comparable amounts. Our carbon and nitrogen measurements indicated that organic solutes are not likely to be present at significant concentrations. The estimated charge of inorganic ions (Na, Mg, P, Cl, K, and Ca) gave a positive net internal charge for most cells. However, in cultures ofVibrio natriegens, the high internal chloride concentration made the net inorganic charge negative in these cells. Our results suggest that growing marine bacterioplankton have an internal environment in which magnesium is the dominating cation. These results suggest that actively growing marine bacteria are physiologically adapted to high internal concentrations of both magnesium and chloride.Key words: X-ray microanalysis, magnesium, osmolyte, marine bacteria.

ISSN:0008-4166    

DOI:10.1139/w99-013

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

A number of nitrogen-fixing bacteria were screened using PCR for genes (vnfGandanfG) unique to the V-containing nitrogenase (vnf) and the Fe-only nitrogenase(anf) systems. Products with sequences similar to that ofvnfGwere obtained fromAzotobacter paspaliandAzotobacter salinestrisgenomic DNAs, and products with sequences similar to that ofanfGwere obtained fromAzomonas macrocytogenes,Rhodospirillum rubrum, andAzotobacter paspaliDNAs. Phylogenetic analysis of the deduced amino acid sequences ofanfGandvnfGgenes shows that each gene product forms a distinct cluster. Furthermore, amplification of an internal 839-bp region inanfDandvnfDyielded a product similar toanfDfromHeliobacterium gestiiand a product similar tovnfDfromAzotobacter paspaliandAzotobacter salinestris. Phylogenetic analysis of NifD, VnfD, and AnfD amino acid sequences indicates that AnfD and VnfD sequences are more closely related to each other than either is to NifD. The results of this study suggest thatAzotobacter salinestrispossesses the potential to express the vanadium (V)-containing nitrogenase (nitrogenase 2) and thatR. rubrum,Azomonas macrocytogenes, andH. gestiipossess the potential to express the Fe-only nitrogenase (nitrogenase 3). LikeAzotobacter vinelandii,Azotobacter paspaliappears to have the potential to express both the V-containing nitrogenase and the Fe-only nitrogenase.Key words: Mo-independent nitrogenase systems, diverse diazotrophs,vnfG,anfG.

ISSN:0008-4166    

DOI:10.1139/w99-007

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Two different anerobic consortia, one removing phenol andortho- (o-) cresol and the other removingpara- (p-) cresol, were cultivated in serum bottles using whey as cosubstrate substitute for proteose peptone. Phenol andp-cresol removal with the phenol-removing consortium were the same with 0.0125% (w/v) whey as with 0.05% proteose peptone. For the other consortium, 8 days were required to decrease thep-cresol concentration from 35 to 2 mg/L with 0.025% whey, while 35 days were required to achieve a similar removal with 0.5% proteose peptone. The two consortia were mixed and cultivated with 0.025% whey. Phenolic compound removal with the mixed consortia was as good as that achieved by each of the two initial consortia against their respective substrates. This removal activity was maintained after several transfers. In a continuous upflow fixed-film reactor, the mixed consortia removed over 98% of 150 mg/L of phenol and 35 mg/L of eacho- andp-cresol in the influent at 29°C, with 0.025% whey as cosubstrate. The hydraulic retention time (HRT) was 0.25 day, corresponding to a phenolic compound volumic loading rate of 880 mg/(L of reactor × day). Once the continuous flow reactor achieved constant phenolic compound removal, no intermediates were found in the effluent, while in serum bottles,m-toluic acid, ano-cresol intermediate, accumulated. Measurements of the specific activity for the uptake of different substrates demonstrated the presence of all trophic groups involved in methanogenic fermentation. These activities were, in mg of substrate/(g of volatile suspended solids × day), as follows: 849 ± 25 for the acidogens; 554 ± 15 for the acetogens; 934 ± 37 for the aceticlastic methanogens; and 135 ± 15 for the hydrogenophilic methanogens. Electron micrographs of the mixed consortia showed seven different morphological bacterial types, includingMethanotrix-like bacteria.Key words: anaerobic degradation, fixed-film reactor, proteose peptone, whey, phenolic compoun

ISSN:0008-4166    

DOI:10.1139/w99-003

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The bacterial community of a zinc-contaminated soil (Maatheide soil in Lommel, Belgium) was studied using cultivation as well as cultivation-independent techniques. Colony-forming units (CFU) were determined by plating on media with or without metals. Dominant isolates were characterized by fatty acid methyl ester analysis (FAME analysis) and PCR fingerprinting using repetitive extragenic palindromic sequences as primers. DNA was directly extracted from soil samples and used as a template for the PCR amplification of the 16S rDNA (8-1511) or a 16S rDNA fragment (968-1401). Clones resulting from cloning the 16S rDNA from soil DNA were sequenced. Temperature gradient gel electrophoresis (TGGE analysis) was performed for 16S rDNA fragments (968-1401) amplified from the dominant isolates, the clones, and the total soil DNA extracted according to two protocols differing in strength of lysis. Total CFU ranged from 104to 105/g soil. The majority of the isolates were identified by FAME analysis asArthrobacterspp. (18 out of 23). None of the isolates were identified as aRalstonia eutrophalike strain (formerlyAlcaligenes eutrophus). MetalloresistantRastomia eutrophalike strains were previously shown to be dominant in the analyzed biotope. Most of the isolates were zinc tolerant but only seven could be considered zinc resistant. Sequences of the 16S rDNA clones obtained from total soil DNA were affiliated with genes of different bacteria such as alpha-proteobacteria, beta-proteobacteria, and theCytophaga-Flexibacter-Bacteroidesgroup. None of the sequenced clones aligned with theRalstonia eutropha16S rRNA gene. TGGE analysis of the 16S rDNA fragments (968-1401) amplified from the dominant strains, the clones, and the total soil DNA showed that isolates and clones represented only a part of the bands present in the TGGE pattern from total DNA. The 968-1401 fragment amplified from allArthrobacterstrains had a similar electrophoretic mobility. This band was seen as a major band in the pattern of DNA extracted from soil using a harsh cell lysis, whereas it did not appear, or appeared only as a weak band, in patterns obtained from soil DNA extracted using gentle lysis. The previously reported predominance of aRalstonia eutrophalike strain in this soil was no longer observed. This may suggest a population replacement by less resistant bacteria, concomitant with a progressive decrease of the zinc toxicity in the Maatheide soil.Key words: microbial community analysis, cultivation, 16S rDNA analysis, TGGE, sequencing, Zn-polluted soil.

ISSN:0008-4166    

DOI:10.1139/w99-012

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Maize seeds were inoculated with a commercial inoculant containing 1.3 × 107Azospirillum lipoferumCRT1 cells. After 24 or 48 h, bacteria were washed from the seed surface. Washed and unwashed seeds were then planted in pots containing perlite and grown for 28 days under greenhouse conditions. Whatever the density ofAzospirillumat planting, the number of these bacteria at the end of the experiment was similar (1.9-8.0 × 107bacteria·plant-1). However, comparison of root surface areas of the plants were different depending on the period of contact between seeds and the density of the inoculum. Twenty-four hours of contact was not sufficient to increase root growth surface areas. Contact for 48 h permitted us to obtain root surface areas comparable with those measured after a continuous contact. These results showed that in order to promote maize root surface areas, an optimal density ofAzospirillumis not required during the whole cultural cycle. This optimal density is indispensable only up to the emergence of the radicle.Key words:Azospirillum, maize, inoculation, PGP

ISSN:0008-4166    

DOI:10.1139/w99-023

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

Hydrogen sulphide formation is a problem in winemaking. One of the factors affecting formation of this unwanted metabolite is the yeast strain responsible for the process. In this experiment wines were made on a laboratory scale with different strains of H2S-producingSaccharomyces cerevisiae. The relationship between H2S production and various fermentation conditions was examined (SO2, methionine, (NH4)2SO4, (NH4)3PO4, steel, and steel-lees). The results show that in fermentations in the presence of stainless steel and lees, H2S formation is high but declines when (NH4)3PO4is added to the must.Key words: H2S formation, wine-yeast, steel-lees, wine-making, alcoholic fermentation.

ISSN:0008-4166    

DOI:10.1139/w99-010

出版商:NRC Research Press    

年代:1999

数据来源: NRC

摘要:

The deduced amino acid sequence ofGluconobacter oxydansRecA protein shows 75.2, 69.4, and 66.2% homology with those fromAquaspirillum magnetotacticum,Escherichia coli, andPseudomonas aeruginosa, respectively. The amino acid residues essential for function of the recombinase, protease, and ATPase inE. coli recAprotein are conserved inG. oxydans.Of 24 amino acid residues believed to be the ATP binding domain ofE. coliRecA, 17 are found to be identical inG.oxydansRecA. Interestingly, nucleotide sequence alignment between the SOS box ofG. orphans recAgene and those from different microorganisms revealed that all the DNA sequences examined have dyad symmetry that can form a stem-loop structure. AG. oxydans recA-deficient mutant (LCC96) was created by allelic exchange using the clonedrecAgene that had been insertionally inactivated by a kanamycin-resistance cassette. Such replacement of the wild-typerecAwith a kanamycin resistance gene in the chromosome was further verified by Southern hybridization. Phenotypically, therecA-deficient mutant is significantly more sensitive to UV irradiation than the wild-type strain, suggesting that therecAgene ofG. oxydansATCC9324 plays a role in repairing DNA damage caused by UV irradiation. Moreover, the mutant strain is much more plasmid transformable than its parent strain, illustrating thatG. oxydansLCC96 could be used as a host to take up the recombinant plasmid for gene manipulation.Key words:Gluconobacter orphans, recAgene, DNA repair,recAmutant, SOS box.

ISSN:0008-4166    

DOI:10.1139/w99-009

出版商:NRC Research Press    

年代:1999

数据来源: NRC