ISSN:0008-4166    

DOI:10.1139/m93-021

出版商:NRC Research Press    

年代:1993

数据来源: NRC

ISSN:0008-4166    

DOI:10.1139/m93-022

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A new intracellular bacteriocin isolated from a human fecal strain ofBacteroides ovatuswas partially purified through ammonium sulfate precipitation, ion exchange chromatography, gel filtration, and preparative polyacrylamide gel electrophoresis (PAGE). The bacteriocin is stable at a pH range of 3–10, at 60 °C for 24 h, and at −70 °C for 6 months. It is inactivated by proteolytic enzymes. The molecular weight, estimated by sodium dodecyl sulfate – PAGE, is 78 kDa. Fifty strains of theBacteroides fragilisgroup were isolated from fecal samples, and 41 of the isolates were shown to produce an antagonistic substance against at least 1 indicator strain. Iso-, auto-, and hetero-antagonisms were observed.Key words:Bacteroides ovatus, bacteriocin, human feces, bacterial growth inhibition.

ISSN:0008-4166    

DOI:10.1139/m93-023

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The metabolic pathway used byRhodococcussp. BPG-8 isolated from oil-rich soil in Newfoundland for the degradation of 1, 3, 5-trihydroxybenzene (phloroglucinol) as a sole source of carbon and energy was determined. Culture filtrate of cells grown on phloroglucinol detected 1, 2, 3, 5-tetrahydroxybenzene when extracted and analyzed using gas chromatography - mass spectrometry, thin-layer chromatography, and ultraviolet spectrophotometry. Nonaromatics were either derivatized with 2, 4-dinitrophenylhydrazine and compared against authentic standards by the above methods, or detected by chemical and enzymatic methods. Extracts of cells grown on phloroglucinol contained phloroglucinol hydroxylase activity, and a dioxygenase that carried out ortho-cleavage of 1, 2, 3, 5-tetrahydroxybenzene. The extract also showed inducible activity for further metabolism of acetopyruvate leading to accumulation of formate in the supernatant. A tentative degradative pathway for phloroglucinol byRhodococcussp. BPG—8 is proposed.Key words: phloroglucinol, 1, 2, 3, 5-tetrahydroxybenzene, degradation,Rhodococcus.

ISSN:0008-4166    

DOI:10.1139/m93-024

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The intracellular pH of the Gram-positive skin bacteriumPropionibacterium acneswas determined using the pH-sensitive fluorescent probe 2′, 7′bis-(2-carboxyethyl)-5-(and-6)carboxyfluorescein (BCECF). The probe was introduced into the bacteria using the membrane-permeable acetoxymethyl ester BCECF-AM. The intracellular pH of the bacteria was determined by establishing a relation between the fluorescence ratio 505/450 and pH using the ionophore nigericin. To verify the intracellular pH determined using BCECF, the results were compared with those obtained using31P-NMR spectroscopy. The effects of different external pH values and glucose addition upon the intracellular pH were examined using BCECF and31P-NMR. Good correlation was obtained between the two techniques.Propionibacterium acnesmaintained a pH gradient, inside alkaline, in the external pH range 5.0–7.4, which inverted when the pH was > 7.5. At external pH ≥ 8.5, the intracellular pH was close to the external pH. Glucose exposure did not affect the intracellular pH. Rapid, transient intracellular acidification and alkalinization brought about using NaHCO3and NH4Cl, respectively, could be detected using BCECF. A limitation encountered when using BCECF was BCECF leakage, which could significantly affect the results if not taken into account.Key words: intracellular pH, BCECF fluorescence,31P-NMR spectroscopy,Propionibacterium acnes.

ISSN:0008-4166    

DOI:10.1139/m93-025

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Factors influencing indoleacetic acid release fromAzospirillum brasilenseCd (ATCC 29729) were investigated under batch culture conditions. In the presence of ammonium in the liquid culture solution, indoleacetic acid release from bacterial cells was considerably higher than in the corresponding N-free medium that was slightly solidified with agar to provide conditions for N2fixation. In the solution culture, the concentration of indoleacetic acid was low during the logarithmic growth phase and increased rapidly with the beginning of the stationary phase. A similar time course was found for the indoleacetic acid content (dry weight basis) of the bacterial cells. Addition of tryptophan strongly stimulated the release of indoleacetic acid, which again showed a steep rise in the early stationary phase. The pH of the nutrient solution increased from 6.8 to 9.3 during incubation but this was not responsible for the steep rise in indoleacetic acid levels. The sole carbon source in the substrate (DL-malic acid) was identified as the limiting growth factor. This suggests that the high increase in indoleacetic acid production in the stationary phase is the expression of an overall change in cell metabolism when the carbon source is exhausted. At this developmental stage the high production of indoleacetic acid seems to have the character of a secondary product. Press sap from wheat roots did not promote indoleacetic acid production by bacterial cells.Key words:Azospirillum, indoleacetic acid, tryptophan, pH solution.

ISSN:0008-4166    

DOI:10.1139/m93-026

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A mercuric ion-reducing flavoprotein was purified fromYersinia enterocolitica138A14 using dye matrix affinity chromatography. The purified enzyme had a characteristic absorption spectrum similar to those of flavin compounds, and FAD was detected as a part of the purified enzyme by thin-layer chromatography. Freshly purified preparations of the enzyme showed a single band on SDS polyacrylamide gel electrophoresis with a molecular weight of 70 000. The isolated enzyme had a molecular weight of about 200 000 as determined by gel filtration and disc gel electrophoresis. These results suggest an apparently trimeric structure of the enzyme. Dithiothreitol treatment disrupted the trimer into a dimeric structure of 140 000. Along with ageing, as well as limited proteolytic digestion, the enzyme evolved to give a dimeric molecule of 105 000 composed of two identical subunits of 52 000. The combination of the purified enzyme with HgCl2, or unexpectedly with merthiolate, oxidised the NADPH, which was followed spectrophotometrically. TheKmfor HgCl2was dependent on the concentration of exogenous thiol compounds. A comparison of physical properties as well as kinetic characteristics indicated that the enzyme fromY.enterocolitica138A14 is similar to mercuric reductases isolated from other mercury-resistant bacteria.Key words:Yersinia enterocolitica, mercury resistance, mercuric reductase.

ISSN:0008-4166    

DOI:10.1139/m93-027

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

We have searched the cloned 86 kilo base pair plasmid pHV1 fromHaloferax volcaniifor repeated sequence elements, of which we expected it to be a rich source. It contains five copies of the previously characterized element ISH51 and a total of five copies of three uncharacterized elements. pHV1 is part of an AT-rich fraction of the DNA that is likely to be a preferred site for IS insertion.Key words:Haloferax volcanii, pHV1 repeated sequence elements, ISH51.

ISSN:0008-4166    

DOI:10.1139/m93-028

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Two bacterial isolates capable of utilizing acrylamide as the sole source of carbon and nitrogen were isolated from herbicide-contaminated soil samples and identified asPseudomonassp. andXanthomonas maltophilia. Batch cultures ofPseudomonassp. andX.maltophiliacompletely degraded 62.8 mM acrylamide to acrylic acid and ammonia in 24 and 48 h, respectively.Pseudomonassp. AndX.maltophilia, when immobilized in calcium alginate, markedly increased the rate of degradation of acrylamide over batch cultures. Cells of the isolates immobilized in calcium alginate degraded acrylamide to acrylic acid and ammonia in less than 6 h. Initial metabolism of acrylamide by immobilized cells ofPseudomonassp. followed by inoculation with nonimmobilized cells after 6 h totally removed acrylamide and its metabolites in 72 h. A similar procedure withX.maltophiliaresulted in the total metabolism of acrylamide in 96 h. An inducible, intracellular amidase was responsible for the hydrolysis of acrylamide to acrylic acid and ammonia. The specific activity ofPseudomonassp. amidase was higher than the specific activity ofX.maltophiliaamidase.Key words: acrylamide, biodegradation, immobilization.

ISSN:0008-4166    

DOI:10.1139/m93-029

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Exoglucanase, a β-1, 4-glucan cellobiohydrolase with specific affinity for β-1, 4-linked glucans, and wheat germ agglutinin, a lectin withN-acetylglucosamine-binding specifity, were used for localizing cellulosic β-1, 4-glucans and chitin in the cell walls of six plant pathogenic fungi. Both chitin and cellulose were found to occur in the cell walls of the oomycete fungusPythium ultimumwhereas only cellulose was present in those ofPhythophthora parasiticavar.nicotianae, another oomycete fungus. The two compounds were also simultaneously detected in the cell walls of two ascomycetes,Ophiostoma ulmiandColletotrichum lindemuthianum. Finally, only chitin could be detected in the cell walls of the ascomyceteFusarium oxysporumf.sp.radicis-lycopersici(FORL) and the basidiomyceteRhizoctonia solani. The dual occurrence of chitin and cellulose inPythium ultimumcell walls was further confirmed by enzymatic extraction performed on isolated cell walls. Treatment ofPythium ultimumcell walls with hen egg white lysozyme, an enzyme with strong chitinolitic activity, prior to labeling with wheat germ agglutinin - ovomucoid - gold complex, resulted in a near abolition of labeling. Similar results were obtained with FORL cell walls used as positive controls to assess the validity of the enzymatic extraction process. When cell walls ofPythium ultimumwere treated with a mixture of hen egg white lysozyme and cellulase, both chitin and cellulose were hydrolysed as shown by the considerable reduction of labeling. Thus, these data provide evidence for the presence of chitin inPythium ultimumcell walls and suggest that classification of Oomycetes as a cellulose-glucan group may be reconsidered.Key words:Pythium ultimum, chitin, cellulose.

ISSN:0008-4166    

DOI:10.1139/m93-030

出版商:NRC Research Press    

年代:1993

数据来源: NRC