摘要:

EnterotoxigenicEscherichia coliwas studied in waste water, river water, and seawater from six locations along the west coast of Normandy by using the polymerase chain reaction (PCR) to amplify the heat labile (LT) gene. Cellular DNA was extracted from centrifugation pellets and amplified using PCR. The PCR products were detected by gel electrophoresis and confirmed by hybridization assay, using an 850 base pairHindIII DNA fragment probe from pEWD299 conjugated to digoxigenin and specific for the LT gene. Results of the PCR amplification were compared with those of GM1 enzyme-linked immunosorbent assay, latex agglutination, and colony hybridization. The PCR method was found to be more precise and less time consuming, especially when compared with methods requiring culture of isolates for enumeration of enterotoxigenicE.coliin water.Key words: enterotoxigenicEscherichia coli, PCR, environmental water, digoxigenin.

ISSN:0008-4166    

DOI:10.1139/m94-040

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Samples of submerged, decaying leaves of red, black, and white mangroves (Rhizophora mangle,Avicennia germinans, andLaguncularia racemosa) were incubated on plates of eight different combinations of fungal inhibitors, bacterial inhibitors, and sporangium inducers added to a standard agar medium for isolating oomycotes (Protoctista: Oomycota; alias Oomycetes). The broad spectrum of agar preparations revealed no new oomycotic species for red or white mangroves;Halophytophthora vesicula(the delicate form) andHalophytophthora spinosawere overwhelmingly the most frequent species (to 88–90%, depending on medium, mangrove, and site). Other described species ofHalophytophthorawere rare (e.g.,Halophytophthora bahamensisoccurred twice, versus a total of 263 occurrences forH.spinosa). For black mangrove, however, the predominant oomycote (frequency ranging up to 90%, depending on medium and site) was an undescribed species ofHalophytophthorawith a mechanism of zoospore release involving the expansion of a clear plug into a tubular vesicle.Halophytophthora vesiculaandH.spinosaoccurred at almost four times lower frequencies on black mangrove than the undescribedHalophytophthoraspecies. Media without inhibitors allowed interference from bacteria and labyrinthulas, with consequent reduction of oomycote frequencies by as much as a factor of four. Chloramphenicol application as the sole inhibitor at 150 mg∙L−1resulted in significant interference from eumycotic fungi (oomycote frequency reductions to × 10). The best medium for exposing maximum frequencies of all three of the principal halophytophthoras was one with amphotericin B (2 mg∙L−1) as the polyene-macrolide fungal inhibitor.Key words: oomycotes, oomycetes,Halophytophthora, mangrove, selective med

ISSN:0008-4166    

DOI:10.1139/m94-041

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Light-induced net H+efflux, photosynthetic oxygen evolution, and medium alkalization during the steady state of photosynthesis were specifically stimulated by K+from pH 6 through 8.5 in the marine cyanobacteriumSynechococcussp. strain UTEX 2380. Net proton efflux in the light was completely abolished by the uncoupler carbonylcyanidem-chlorophenylhydrazone and the membrane ATPase inhibitor diethylstilbestrol or partially abolished by the membrane ATPase inhibitorN,N′-dicyclohexyl-carbodiimide and by orthovanadate. H+extrusion in the light was accompanied by K+uptake at rates of 30 μmol∙mg chlorophyll−1∙h−1. During the steady state of CO2fixation, potassium was excreted simultaneously with medium alkalization. The K+content of the cells was 432 mM for air-grown cells. K+in the cells was displaced by diethanolamine, which was inhibited bym-chlorophenylhydrazone. Na+-loaded cells showed nearly complete inactivation of oxygen evolution and medium alkalization. Both activities were reactivated by the addition of K+or Rb+. A fivefold increase in inorganic carbon uptake in the light was observed in the presence of K+. The pH of the cytoplasm in the light increased from 7.2 to 8.04 in the pH range 6.6–8.6. These results suggest that a light-dependent, proton-excreting ATPase is active in conjunction with a K+uptake system in a marineSynechococcusspecies, while a K+–H+antiporter may function as a regulator of cytoplasmic pH during photosynthesis.Key words: potassium transport, oxygen, cyanobacterium,Synechococcus, proton extrus

ISSN:0008-4166    

DOI:10.1139/m94-042

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Cell surface hydrophobicity influences adhesion and virulence of the opportunistic fungal pathogenCandida albicans. Previous studies have shown that cell surface hydrophobicity is due to specific proteins that are exposed on hydrophobic cells but are masked by long fibrils on hydrophilic cells. This observation suggests that hydrophobic cell wall proteins may contain little or no mannosylation. In the present study, the glycosylation levels of three hydrophobic cell wall proteins (molecular mass range between 36 and 40 kDa) derived from yeast cells were examined. One hydrophilic protein (90 kDa) was also tested. Various endoglycosidases (endoglycosidase F –N-glycosidase F,O-glycosidase, β-mannosidase,N-glycosidase F), an exoglycosidase (α-mannosidase), and trifluoromethane sulfonic acid were used to deglycosylate the proteins. All four proteins were reactive to the lectin concanavalin A, demonstrating that they were mannoproteins. However, gel electrophoresis of the control and treated proteins revealed that mannosyl groups of hydrophobic proteins were less than 2 kDa in size, while the mannosyl group of the hydrophilic protein had a molecular mass of approximately 20 kDa. These results suggest that unlike many hydrophilic proteins, hydrophobic proteins may have low levels of glycosylation. Changes in glycosylation may determine exposure of hydrophobic protein regions at the cell surface.Key words:Candida albicans, cell wall, mannoproteins, hydrophobicity, fibrils.

ISSN:0008-4166    

DOI:10.1139/m94-043

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A mesophilic, irregular coccoid methanogen, which shows close resemblance toMethanococcussp., was isolated from a sediment sample of St. Joseph Lake located in the University of Notre Dame campus. Formate or hydrogen plus carbon dioxide served as substrate for methanogenesis in a mineral salt medium. This organism was studied for its ability to metabolize 2,4,6-trinitrotoluene (TNT). The result showed that this isolate could transform 100 ppm of TNT within 40–60 days of incubation at 30 °C. The main intermediate produced was 2,4-diamino-6-nitrotoluene. The TNT transformation rates were higher in cells grown in hydrogen plus carbon dioxide than in cells grown in formate. The isolate did not use acetate and methanol as sole source of carbon and energy. The organism had an optimal pH range of 6.8–7.2. The optimal growth conditions for this isolate are described.Key words: biotransformation, methanogens, bioremediation, nitroaromatics, TNT, anaerobic process.

ISSN:0008-4166    

DOI:10.1139/m94-044

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The effect of resistance plasmids encoding copper resistance (Cur), streptomycin resistance (Smr), and both Curand Smron competitive fitness ofPseudomonas syringaepv.syringaewas studied in vitro and in planta. The CurSmrplasmid pPSR1 provided a selective advantage to its bacterial host (Pseudomonas syringaepv.syringaeFF5.1) onPyrus calleryanaleaves that were treated weekly with copper and (or) streptomycin bactericides. However, populations of the plasmid-free CusSmsFF5.1 were reduced 10- to 1000-fold over a 12-week period on trees treated with bactericides. The resistance plasmids pPSR4 (Cur), pPSR5 (Smr), and pPSR4::Tn5393(CurSmr) were highly stable for over 200 generations of growth in glucose-limited batch culture. Results of competition experiments in vitro indicated thatPseudomonas syringaepv.syringaeFF5 containing pPSR4, pPSR5, or pPSR4::Tn5393was reduced to less than 5% of the total culture in competition with wild-type FF5. In growth chamber studies, the resistance plasmids studied did not have an impact on epiphytic fitness ofPseudomonas syringaepv.syringae. Our data suggest that resistance plasmids will persist in populations ofPseudomonas syringaepv.syringaefollowing their initial selection regardless of the bactericidal spray regime.Key words: competitive fitness, epiphytic fitness, copper and streptomycin resistance.

ISSN:0008-4166    

DOI:10.1139/m94-045

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Thirty-fiveEscherichia coliisolates from young children and women with pyelonephritis, cystitis, or asymptomatic bacteriuria were characterized genotypically and phenotypically. The isolates were examined genotypically by using DNA probes specific for the hemolysin gene and for thepap,sfa, andafaadhesin systems. Genes for the adhesin systems were also detected by polymerase chain reaction, using multigene amplification. The isolates were serotyped, tested for hemolysin production, and classified for their adhesion specificity by hemagglutination and by binding specificity assays. Twenty-seven of the 35 isolates werepappositive. Results showed thatpap-positive isolates expressing class I or class II G adhesins were more frequent in cases of pyelonephritis than in cases of cystitis and asymptomatic bacteriuria. Expression of the class III G adhesins was more frequent in isolates from cystitis and asymptomatic bacteriuria than in isolates from pyelonephritis. Multiple adhesin systems and hemolysin were more frequently found in isolates from cases of pyelonephritis than in isolates from cases of cystitis and asymptomatic bacteriuria. There was perfect correlation between the results obtained by polymerase chain reaction and and those obtained by hybridization.Key words:Escherichia coli, UTI, fimbriae, PCR, virulence factors.

ISSN:0008-4166    

DOI:10.1139/m94-046

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Urokinase is a proteinase that normally functions as a plasminogen activator. It is detected in a number of tissues and can be expressed by inflammatory cells such as macrophages and polymorphonuclear leucocytes. Addition of human urokinase to cultures of mucoid or nonmucoid variants ofPseudomonas aeruginosa(strain PAO and clinical isolates from patients with cystic fibrosis) orPseudomonas cepaciaincubated in a minimal medium under nonshaking (oxygen limited) conditions led to dose-dependent enhancement of bacterial growth. The enzyme exhibited a minimal effect on the growth of bacteria when cultured under more intense aeration conditions. This enhancement of bacterial growth by urokinase required the presence of active enzyme and was not detected with inactivated enzyme or noncatalytic domains of the enzyme. Enhancement of bacterial growth was not observed following incubation ofP.aeruginosawith other proteinases including thrombin, neutrophil elastase, trypsin, chymotrypsin, or pseudomonas elastase and pseudomonas alkaline proteinase. Therefore, the observed effect of urokinase was relatively specific for this enzyme. As urokinase is a natural constituent of the lung, this enzyme could contribute to bacterial growth during pulmonary infections, particularly in an inflammatory environment in which the oxygen tension may be reduced.Key words: plasminogen activators,Pseudomonas aeruginosa, bacterial growth, urokinase, host proteinases.

ISSN:0008-4166    

DOI:10.1139/m94-047

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The ruminal fungiNeocallimastix frontalisRE1,Neocallimastix patriciarum27,Piromyces communis22, andOrpinomyces joyonii19-2 were examined for their ability to digest filter paper in the presence of condensed tannins from birdsfoot trefoil (Lotus corniculatusL.). For all four fungi, inhibition of endoglucanases was evident at 100 μg condensed tannins∙mL−1with nearly complete inhibition at 300 μg condensed tannins∙mL−1. At 100 and 200 μg condensed tannins∙mL−1, the endoglucanase activity ofN.frontalisRE1 was greater (P < 0.01) than that of the other three fungal species. Exposure to 100 μg condensed tannins∙mL−1did not affect the ability ofN.frontalisRE1 orN.patriciarum27 to digest filter paper, and although digestion was reduced,N.frontalisRE1 andP.communis22 solubilized more than 20% of the filter paper at 500 μg condensed tannins∙mL−1. In contrast,O.joyonii19-2 was virtually unable to digest filter paper at 300 μg condensed tannins∙mL−1. Mycelia of fungi grown with condensed tannins were covered by filamentous material, which may have arisen from the formation of condensed tannin–protein complexes. Less than 86% of the condensed tannins (as measured by the H2SO4method) were recovered after 120 h of incubation withN.frontalisRE1,P.communis22, andN.patriciarum27. The need for detailed studies to examine the ability of ruminal fungi to metabolize condensed tannins is evident.Key words: ruminal fungi, condensed tannins, cellulose digestio

ISSN:0008-4166    

DOI:10.1139/m94-048

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The F390synthetase activity in cell extracts ofMethanobacterium thermoautotrophicumMarburg increased by two times upon preincubation at 37 °C with its substrates, ATP (or GTP) and coenzyme F420, but not with either of these compounds alone. In the 0–37 °C range, preincubation at 37 °C gave maximal enhancement in activity. F390synthetase activity in cell extracts of strain Marburg was maximal at 45 °C, whereas F390synthetase fromM.thermoautotrophicumΔH had maximal activity at 55 °C; both strains grew optimally at 65 °C. Data derived from the Arrhenius plot supported our earlier conclusion that the F390synthetase activity of strain Marburg could lead to a loss of 70% of the available F420during extraction of this factor from cells via an aerobic cell extract procedure even if the temperature was maintained at 4 °C.Key words:Methanobacterium thermoautotrophicum, F390synthetase, activation, coenzyme F420

ISSN:0008-4166    

DOI:10.1139/m94-049

出版商:NRC Research Press    

年代:1994

数据来源: NRC