摘要:

Aquatic biofilms, which are widespread not only in nature but also in medical and dental devices, can be the source of serious nosocomial infections. In these hardy microbial communities, pathogens like nontuberculous mycobacteria,Pseudomonas aeruginosa,Legionella pneumophila, and other bacteria not only survive but proliferate and lie in wait for susceptible hosts. Not only are these organisms intrinsically resistant to high temperatures and biocides, but the biofilms they inhabit enhance their resistance. This should be of concern to infection control practitioners. The bacterial colonization of dental unit waterlines can be used as a model to investigate the problem of waterborne biofilms in health care settings.Key words: dental unit waterlines, biofilm, nosocomial pathogens, drinking water.

ISSN:0008-4166    

DOI:10.1139/w98-101

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The antimutagenicity and fermentation pattern of threeBifidobacterium longumstrains (B. longum,B. longumPS+, andB. longumPS-) in skim milk were studied. The increase in fermentation time significantly increased antimutagenicity with all strains tested against the mutagenicity of both 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) in an Ames-like test using streptomycin-dependent strain SD510 ofSalmonella typhimuriumTA98.Bifidobacterium longumPS+, a polysaccharide-producing strain, had a longer lag phase but showed the highest inhibition percentage against both mutagens tested. The viability ofB. longumPS+cells was not affected by the low pH of 4.1, probably owing to the protection offered by the polysaccharide produced. The antimutagenicity of the fermented milk against Trp-P-1 was dose dependent. The strains were also able to bind with different amino acid pyrolysates, andB. longumshowed the highest binding. Acetone extracts of fermented skim milk dissolved in water showed less antimutagenicity than extracts dissolved in dimethylsulfoxide. The isolated crude polysaccharide fromB. longumPS+showed a dose-dependent inhibition of the mutagenicity of Trp-P-1. Thus, we conclude that the polysaccharide ofB. longumPS+can be used as an antimutagen.Key words:Bifidobacterium longum, polysaccharides, fermented milk, heterocyclic amines.

ISSN:0008-4166    

DOI:10.1139/w98-103

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The first report of the gene inactivation system (GIS) inAspergillus nidulanscame from crosses involving a II Gene inactivation system extension into a unique sequence outside of the II →> I insertional duplication. Duplicated segments trigger the GIS that acts through the methylation of cytosines present within repeats. Duplicated genes are probably inactivated during the premeiotic period between fertilization and karyogamy, but reactivation may occur spontaneously or after 5-azacytidine treatment. The aim of the present study was to determine the action of GIS on a single copy gene located near a duplicated segment.Aspergillus nidulansstrains bearing the Dp(II,I) duplication were used in meiotic crosses homozygous for they+gene and yellow (y) segregants were recovered among the progenies. Data show that the GIS can act on a closely linked gene outside the duplicated segment, promoting reversible inactivation. Reduction of ascospore numbers and viability were observed in crosses parented by duplication strains. Inactivation of thew+gene in aw/w+duplication strain is also shown.Key words:Aspergillus nidulans, gene inactivation, DNA methylation, chromosomal duplication.

ISSN:0008-4166    

DOI:10.1139/w98-099

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Genetic hybridization and karyotypic analyses revealed the biological speciesSaccharomyces paradoxusandSaccharomyces cerevisiaein exudates from North American oaks for the first time. In addition, two strains collected from elm flux and fromDrosophilaby Phaff in 1961 and 1952 were reidentified asS. paradoxus. Each strain studied showed a unique profile of chromosomal hybridization with a probe for the retrotransposable element Ty1. The wild distribution of naturalSaccharomycessensu stricto yeasts is discussed.Key words: genetical taxonomy,Saccharomyces paradoxus, oak exudates, Ty elements, electrophoretic karyotyping.

ISSN:0008-4166    

DOI:10.1139/w98-104

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The hyphae of the snow moldMicrodochium nivalecontained lipids in a yield of about 10% w/w of the dry matter of hyphae. The total lipid was fractionated into neutral and polar lipid fractions. In the neutral lipid fraction, triacylglylcerol was the sole major component. As minor components, ergosterol, diacylglycerol, free fatty acid, and fatty acyl ergosterol were identified. The polar lipid fraction contained phospholipids, glycolipids, and a lipid containing neither phosphorus nor sugar. Phosphatidylethanolamine, phosphatidylcholine, phosphatidylglycerol, phosphatidylserine, and phosphatidic acid were identified as phospholipids. The polar lipid fraction included at least four kinds of glycolipids that have not been identified. A very unusual lipid in fungi, a betaine lipid, diacylglyceryltrimethylhomoserine, was identified by chemical and physicochemical analyses. The level of the neutral lipid fraction, which accounted for 60% of the total lipid in hyphae at the exponential phase, was significantly increased compared with that of the polar lipid fraction and constituted 80% of the total at the stationary phase. The neutral and polar lipids ofMicrodochium nivalecontained 18:3 (9,12,15), 18:2 (9,12), 18:1 (9), and 16:0 as principal fatty acids. Among them, 18:2 (9,12) and 18:3 (9,12,15) were the major fatty acids of triacylglycerol, phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine, whereas in diacylglyceryltrimethylhomoserine, the major components were 16:0 and 18:3 (9,12,15).Key words: snow mold, phospholipids, betaine lipid, fatty acid,Microdochiumnivale.

ISSN:0008-4166    

DOI:10.1139/w98-094

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The effects of diamine (R1-NH-R2-NH2) biocides A and B on the microbial population from an oil field were investigated with reverse sample genome probing (RSGP), a technique designed to track multiple oil field bacteria in a single assay. RSGP studies of sessile microbial populations scraped from corrosion coupons obtained from biocide-treated oil field installations indicated dominance ofDesulfovibriospp. Lac6 and Eth3, or of selected heterotrophs. RSGP of planktonic production water samples indicated a broad distribution of microorganisms that changed with the addition of medium for the growth of sulfate-reducing bacteria, containing different organic acids as electron donors for sulfate reduction. Use of lactate, propionate, or acetate enrichedDesulfovibriospp.,Desulfobulbussp. Pro4, orDesulfobacterspp., respectively. Treatment of lactate- or mixed organic acid-fed planktonic populations with biocides indicated resistance of Lac6 and Eth3 to 400 ppm of biocide B and 40 ppm of biocide A. The dominance of these twoDesulfovibriospp. in many sessile field samples is, therefore, likely caused by biocide selection.Key words:Desulfovibrio, sulfate reduction, microbial corrosion, souring, biocide.

ISSN:0008-4166    

DOI:10.1139/w98-105

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

Antibiotic susceptibility tests and restriction enzyme analysis (REA) of genomic DNA were performed to characterize the relationship between sources of isolates of yellow-pigmented enterococci. Antibiotic susceptibility tests were conducted with 10 therapeutic antibiotics and 54 isolates grouped by source (wild and other) depending on their origin. In three antibiotics, cephalothin, erythromycin, and vancomycin, there was a significant (p=< 0.05) association between susceptibility and source. Vancomycin resistance was significantly (p=< 0.001) higher in isolates from wild sources compared with that in isolates from other sources. The REA technique was performed on genomic DNA obtained from 17Enterococcus mundtiiisolates from: human (3), dog (4), horse (4), Canada goose (4), domestic goose (1), andEnterococcus mundtiiATCC 43186. A total of 12 different DNA types (A-L) were identified. Except for type D, 11 DNA types were unique and were distributed among dog (A, B, and C), human (E), horse (F, G, and H), Canada goose (I, J, and K), and domestic goose (L). Results suggested that vancomycin-susceptibility testing of yellow-pigmented enterococci may have potential value in the identification of sources of faecal pollution, especially when combined with traditional quantitative methods.Key words: yellow-pigmented enterococci, faecal pollution, antibiotic susceptibility, DNA typing.

ISSN:0008-4166    

DOI:10.1139/w98-107

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The types of metabolites produced byPhotorhabdus luminescensC9 when it is introduced byHeterorhabditis megidis90 intoGalleria mellonellalarvae are different from those produced in tryptic soy broth. Only 3,5-dihydroxy-4-isopropylstilbene1was identified from the organic extracts ofP.luminescensculture broth, but both 3,5-dihydroxy-4-isopropylstilbene1and 3,5-dihydroxy-4-ethylstilbene3were isolated from the organic extracts of nematode-bacterium infectedG.mellonellalarvae. In addition to two pigments, both of which had been previously reported fromP.luminescensC9 culture broth, three pigments, 1,8-dihydroxy-3-methoxy-9,10-anthraquinone2, 1-hydroxy-2,6,8-trimethoxy-9,10-anthraquinone6, and 1,4-dihydroxy-2,5-dimethoxy-9,10-anthraquinone7were isolated from the organic extracts ofG.mellonellalarvae infected by the nematode-bacterium complex. Among these, compounds6and7are novel and isolated from a natural source for the first time.Key words:Photorhabdus luminescens,Heterorhabditis megidis, 1-hydroxy-2,6,8-trimethoxy-9,10-anthraquinone, 1,4-dihydroxy-2,5-dimethoxy-9,10-anthraquinone, pigment.

ISSN:0008-4166    

DOI:10.1139/w98-098

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

The arginine deiminase system in oral streptococci is highly regulated. It requires induction and is repressed by catabolites such as glucose or by aeration. A comparative study of regulation of the system inStreptococcus gordoniiATCC 10558,Streptococcus rattusFA-1, andStreptococcus sanguisNCTC 10904 showed an increase in activity of the system inS.sanguisof some 1467-fold associated with induction-derepression of cells previously uninduced-repressed. The activity of the system was assayed in terms of levels of arginine deiminase, the signature enzyme of the system, in permeabilized cells. Increases in enzyme levels associated with induction-derepression were less for the other two organisms, mainly because of less severe repression, especially forS.rattusFA-1, which was the least sensitive to catabolite repression or aeration. Regulation of the arginine deiminase system involving induction and catabolite repression was demonstrated also with monoorganism biofilms composed of cells ofS.sanguisadherent to glass slides. Fully uninduced-repressed cells from suspension cultures or biofilms were compromised in their abilities to catabolize arginine to protect themselves against acid damage. However, it was found that the system can be rapidly turned on or turned off, although induction-derepression did appear to require cell growth. Still, the system could respond rapidly to the availability of arginine to reestablish high capacity for alkali production.Key words: arginine deiminase, oral streptococci, induction-derepression, acid damage, biofilms.

ISSN:0008-4166    

DOI:10.1139/w98-106

出版商:NRC Research Press    

年代:1998

数据来源: NRC

摘要:

TThe uptake of naphthalene has been investigated in the metabolizing cells ofPseudomonas fluorescensutilizing [1-14C]naphthalene. The uptake displayed an affinity constant (Kt) of 11 &mgr;M and a maximal velocity (Vmax) of 17 nmol·h-1·mg-1cellular dry weight. Naphthalene uptake was not observed in a mutant strain, TG-5, which was unable to utilize naphthalene as a sole source of carbon for growth. Uptake was significantly inhibited (~90%) by the presence of growth-inhibiting levels of either azide or 2,4-dinitrophenol and was sensitive to the presence of structural analogues of naphthalene. The intracellular levels of ATP were not significantly reduced by the presence of either azide or 2,4-dinitrophenol. The presence of alpha-naphthol was found to noncompetitively inhibit naphthalene uptake, displaying aKiof 0.041 &mgr;M. It is concluded that the first step in the utilization of naphthalene byPseudomonas fluorescensis its transport into the cell by a specific energy-linked transport system.Key words: naphthalene, PAH, biodegradation, transport.

ISSN:0008-4166    

DOI:10.1139/w98-110

出版商:NRC Research Press    

年代:1998

数据来源: NRC