摘要:

Enterococci, fomerly confounded with faecal streptococci, are recognized since the beginning of the century as being faecal in origin and are generally searched for in waste waters and food products; their detection may in fact indicate the presence of enteropathogenic organisms. Although nearly ubiquitous, their preferred ecological niche is the intestine sphere. Rejected in the environment by means of human faeces or animal dejecta, they are scattered afterwards in diverse niches. Once in the external environment, their survival is linked with their exceptional aptitude to resist or grow in hostile environments that are usually detrimental to the development of most mesophilic microorganisms. However, a certain ambiguity exists concerning their relationships with human beings. In fact, certain enterococcus strains or species are used in the elaboration of some milk products. Conversely, others are opportunists and may cause severe infections to people from infants to adults. Moreover, undergoing adaptation perpetually, they present a multiresistance pattern to antibiotics. Thus, the barrier that separates bacteria as nonoffensive contaminants from powerful pathogens appears most fragile, suggesting that people must systematically consider suspect the presence of enterococci in their near environment.Key words: enterococci, biochemical properties, resistance, biotopes, opportunism.

ISSN:0008-4166    

DOI:10.1139/m97-101

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Proteus mirabilisis a common causative agent of human urinary tract infections, especially in catheterized patients and in those patients with structural abnormalities of the urinary tract. In addition to the production of hemolysin and urease, fimbriae-mediated adherence to uroepithelial cells and kidney epithelium may be essential for virulence ofP.mirabilis. A singleP.mirabilisstrain is capable of expressing several morphologically distinct fimbrial species, which can each be favoured by specific in vitro growth conditions. The fimbrial species reported to date include mannose-resistant/Proteus-like fimbriae, ambient temperature fimbriae,P.mirabilisfimbriae, and nonagglutinating fimbriae (NAF). Here, using intact bacteria or purified NAF as immunogens, we have generated the first reported NAF-specific monoclonal antibodies (mAbs). Bacteria expressing NAF as their only fimbrial species adhered strongly to a number of cell lines in vitro, including uroepithelial cell lines. Binding ofP.mirabiliswas markedly reduced following preincubation with NAF-specific mAbs and Fab fragments. The presence of NAF with highly conserved N-terminal sequences on allP.mirabilisstrains so far examined, combined with the ability of both anti-NAF mAbs and purified NAF molecules to inhibitP.mirabilisadherence in vitro, suggests that NAF may contribute to the pathogenesis ofP.mirabilis.Key words: fimbriae, adherence, monoclonal antibodies,Proteus mirabilis, receptors.

ISSN:0008-4166    

DOI:10.1139/m97-102

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Twenty transformants obtained by transforming theargBstrain ofAspergillus nidulansby the biolistic process were analysed in detail. Eight lost the Arg+phenotype very frequently and the other 12 were mitotically stable, even after 15 successive subculturing. To analyse the integration events, the mitotically stable transformants were submited to genetic and molecular analyses; 16.7% resulted from the integration of the transforming DNA in tandem with the chromosomalargBlocus, 8.3% showed replacement of theargBmutation by wild type allele, 41.7% showed transforming DNA integrated into nonhomologous chromosomal regions at chromosome III, and 33.3% showed transforming DNA integrated into nonhomologous chromosomal regions at chromosomes others than III. Among the mitotically stable transformants, the frequency of integration into nonhomologous sites was higher by the biolistic process than that reported by the literature for protoplast-mediated transformation.Key words:Aspergillus nidulans, fungal transformation, biolistic gene transfer, gene integration,argBgene.

ISSN:0008-4166    

DOI:10.1139/m97-103

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Identification of some economically importantTuberspecies using classical morphological characteristics is sometimes difficult. We report here the molecular characterization of a species coming from China,Tuber indicum, mistaken withTuber melanosporumspecies. Using restriction analysis of the amplified internal transcribed spacer (ITS) of rDNA, ITS sequence analysis, and sequence characterized amplified region markers, with DNA from fruit bodies or mycorrhizae, genetic variation was found between these two species, allowing to differentiate and characterize them.Key words: molecular identification,Tuber, internal transcribed spacer, sequence characterized amplified region.

ISSN:0008-4166    

DOI:10.1139/m97-104

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Leukotoxic activity was assayed in clinical isolates ofEnterobacter cloacae. Two strains were selected out of 38 by their greater hemolytic activity in blood agar plates. Leukotoxin was purified by salt precipitation, dialysis, chromatography by gel filtration, and high pressure liquid chromatography (HPLC). Human leukocytes, when incubated with purifiedE.cloacaetoxin, showed high percentages of death and lysis, with time and dose dependence. The chromatographic profile of gel filtration presented three protein peaks and toxic activity was detected in the second peak. After HPLC, leukotoxin coeluted with the hemolytic activity and both activities were detected only after 2-mercaptoethanol treatment. Coomassie-stained sodium dodecyl sulfate – polyarylamide gels showed a single band. This band was estimated to represent a protein of 13 300 Da on the basis of both sodium dodecyl sulfate – polyacrylamide gel electrophoresis and gel filtration chromatography.Key words:Enterobacter clocae, leukotoxin, molecular mass, cytotoxin, leukocytes.

ISSN:0008-4166    

DOI:10.1139/m97-105

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

We have cloned the inorganic pyrophosphatase gene (ppa) from the facultative intracellular pathogenBartonella bacilliformisand characterized its encoded product. The 531-bp gene is located approximately 1 kb downstream of, and in opposite orientation to, the invasion-associated locus (ialAB) ofB.bacilliformis. The predicted protein encoded byppais 177 amino acid residues, which is in agreement with in vitro and in vivo synthesis of a protein with an apparent molecular mass of 22–23 kDa. The predictedB.bacilliformispyrophosphatase (PPase) sequence is 53% identical and 85% similar to theE.coliPPase (EC 3.6.1.1), and contains all 12 of the amino acid residues implicated in the catalytic active site. The isolatedB.bacilliformisPPase exhibits an activity of 51 ± 2 μmol PO4released/(mg protein∙min) at 28 °C and pH 8, and is sensitive to inhibition by Ca2+. In keeping with other prokaryotic PPases,B.bacilliformisPPase activity occurs from pH 6 to 10 (optimal pH = 8) and demonstrates high thermostability in the presence of Mg2+(highest activity at 55 °C, relative activity = 80 ± 3% at pH 8). The clonedB.bacilliformis ppais able to genetically complement appa−mutant strain ofE.coli.Key words:Bartonella, invasion-associated locus, inorganic pyrophosphatas

ISSN:0008-4166    

DOI:10.1139/m97-106

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

The distribution of protein antigens in purified subcellular fractions ofMycobacterium bovisbacillus Calmette–Guérin (BCG) was comparatively analysed by sodium dodecyl sulfate – polyacrylamide gel electrophoresis and immunoblotting with specific monoclonal antibodies and polyclonal sera. The 19- and 38-kDa lipoproteins were mainly detected in the cell wall and cell membrane enriched fractions, and they were extracted from the former by Triton X-114 and Nonidet P-40. The 65-kDa heat-shock protein (hsp) was present in the cytoplasmic fraction and only trace amounts were found in the crude cell wall preparation. In contrast, the 14-kDa hsp was highly represented in the cell wall fraction, besides being present in cytoplasmic fraction. Both superoxide dismutase (SOD) and antigen 85 complex (Ag 85) were abundantly released in culture medium, and to a lower extent, they were present in the cell wall fraction; SOD was present in comparable amounts also in the cytoplasmic fraction, while Ag 85 was far less represented in the same. Sera from mice immunized with culture filtrate (CF) proteins of BCG recognized several antigens in CFs, which were not detectable in cell wall, cell membrane, and cytoplasmic fractions, indicating that CF proteins include secreted antigens which have not yet been identified.Key words: bacillus Calmette–Guérin, monoclonal antibodies, subcellular localization.

ISSN:0008-4166    

DOI:10.1139/m97-107

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

This study examines the controversial efficacy of chlorine and monochloramine against biofilms that differ in their extracellular polysaccharide (EPS) content. The results point out a net variability of bacterial biofilm susceptibility according to the nutrients present. Chlorine and monochloramine showed an equal biocidal activity on lactose medium-grownE.coliATCC 10 536 and glycerol – ammonium nitrate medium-grown nonmucoidPseudomonas aeruginosabiofilms. In contrast, the effect of monochloramine is greater compared with that of chlorine onE.coliand mucoidP.aeruginosabiofilms grown in sucrose and glycerol – ammonium nitrate media, respectively. In these culture conditions, treatment with 25 mg monochloramine/L for 2 h reduced culturable cells by 4.5 logs (99.997%) forE.coliand about 3 logs (99.87%) for mucoidP.aeruginosawhile the similar treatment with chlorine reduced culturable cells in these biofilms by 2.2 logs (99.4%) and 1 log (10%), respectively. The decrease of chlorine disinfection efficacy on sucrose and glycerol – ammonium nitrate medium-grown biofilms is postulated to be linked to the higher polysaccharide production observed in these media. It seems likely that monochloramine produces a high leakage of material absorbing at 260 nm from sucrose medium-grownE.colibiofilm, which could indicate its better penetration into biofilms.Key words: biofilm, chlorine, monochloramine,E.coli, mucoidPseudomonas aeruginosa.

ISSN:0008-4166    

DOI:10.1139/m97-108

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

Nitrogen fixation was measured in different habitats in the area of Ny-Ålesund, Spitsbergen, using the acetylene reduction method on intact soil cores andNostoc communegrowing in macroscopic sheet communities. The samples were incubated both under constant conditions (19 °C and 200 μE∙m−2∙s−1) and under in situ conditions. Cyanobacteria were considered to be the major nitrogen-fixing organisms. The nitrogen fixation rates showed a seasonal variation during the growing season of 1994, with low activities just after the snow melt, increasing until the middle of August and showing a rapid decline after the snow fell on August 29. The soil temperature at the time of sampling showed a positive, linear correlation with the nitrogen fixation activities measured on intact soil cores, whereas the nitrogen fixation activities measured in situ ofN.communeshowed a positive, linear dependence on the moisture content in the sheets and the incubation temperatures inside the incubation vessels during the experiments. The optimal temperature of the nitrogen fixation activity was about 20 °C, both forN.communeand aPuccinelliasalt marsh. The highest nitrogen fixation rate measured in situ was at a patterned ground, which had the highest pH, the highest concentrations of extractable calcium and magnesium, and the highest C:N ratio measured.Key words: nitrogen fixation, cyanobacteria,Nostoc commune, high arc

ISSN:0008-4166    

DOI:10.1139/m97-109

出版商:NRC Research Press    

年代:1997

数据来源: NRC

摘要:

A new antibiotic, nematophin, was isolated from strain BC1 ofXenorhabdus nematophilusand detected in all strains ofX.nematophilusstudied. Its structure is fully established as 3-indoleethyl (3′-methyl-2′-oxo)pentanamide by extensive spectroscopic study. The production of nematophin is affected by the strain type and culture conditions. The compound shows strong in vitro bioactivity against a series of fungal and bacterial species.Key words: nematophin, symbiotic bacteria,Xenorhabdus nematophilus, antibiotic.

ISSN:0008-4166    

DOI:10.1139/m97-110

出版商:NRC Research Press    

年代:1997

数据来源: NRC