摘要:

Cell survival and plasmid stability inPseudomonas fluorescensR2f andPseudomonas putidaCYM 318 containing respectively, plasmid RP4 and pRK2501, andKlebsiella aerogenesNCTC 418 harboring plasmid pBR322 were studied in sterile and nonsterile agricultural drainage water under both aerobic and anaerobic conditions and in the absence and presence of added nutrients. BothPseudomonasstrains survived well in sterile drainage water incubated aerobically, with or without added nutrients. However,Klebsiella aerogenesNCTC 418 (pBR322) only survived in the presence of added nutrients.Pseudomonas fluorescensR2f (RP4) andK.aerogenesNCTC 418 (pBR322) did not survive under anerobic conditions without added nutrients, but showed good survival in the presence of nutrients. Survival of all three strains was negatively affected in nonsterile agricultural drainage water when compared with survival in sterile water. Maintenance of the three plasmids was host, plasmid, and environment dependent. Plasmid pBR322 was not stably maintained inK.aerogenesNCTC 418 under all conditions used in the study, and pRK2501 was readily lost fromP.putidaCYM 318. Maintenance of RP4 byP.fluorescensR2f was markedly influenced by added nutrients, which caused a loss of the plasmid from cells. The results of the present study demonstrate the influence of nutrients, O2, and native microorganisms on the survival of introduced bacterial strains and plasmid stability in agricultural drainage water.Key words: bacteria, survival, stability, plasmids, water.

ISSN:0008-4166    

DOI:10.1139/m89-110

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Several gene probe methods were used to monitor specific microbial populations in freshwater microcosms. Detection methods included nonselective plating – colony hybridization, selective plating – colony hybridization, most probable number – filter hybridization, and community DNA extraction – dot blot hybridization. Tests were conducted in freshwater microcosms inoculated with a 4-chlorobiphenyl degradingAlcaligenesA5 or a 2,4,5-trichlorophenoxyacetic acid degradingPseudomonas cepaciaAC1100. Colony hybridization performed on colonies detected on a nonselective medium sometimes failed to detect bothAlcaligenesA5 andP.cepaciaAC1100 when the target populations comprised less than 0.1% of the total population, even though the target populations comprised less than 0.1% of the total population, even though the target populations were present at concentrations of greater than 104viable cells/mL as indicated by other detection methods. Selective plating – colony hybridization, most probable number – filter hybridization, and dot blot hybridization using DNA extracted from the microbial community consistently indicated persistence of the addedP.cepaciaAC1100 in the microcosms. Although differing in their detection reliability and sensitivity, the various gene probe detection methods indicated persistence with a slow decline of both theAlcaligenesA5 andP.cepaciaAC1100 over an 8-week period.Key words: DNA probes, environmental, bacteria, detection, biodegradation.

ISSN:0008-4166    

DOI:10.1139/m89-111

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Rumen ciliate populations were surveyed in 11 Holstein cattle and 6 sheep in Lethbridge (Alta., Canada) to determine species distribution in this Western Canadian environment. A total of 28 ciliate species were identified in cattle and 17 in sheep. The average total number of ciliates per millilitre of rumen content was 6.9 × 104in cattle and 1.9 × 105in sheep. The average number of species per host was 20.5 in cattle and 13.8 in sheep. Of the ciliate species detected, species ofEntodiniumappeared most frequently both in cattle and in sheep.Diplodinium polygonale,Eodinium lobatum,Eo.monolobum,Eremoplastron rostratum,Ostracodinium clipeolum,Os.mammosum, andOphryoscolex purkynjeiwere not detected in sheep. In contrast,Ophryoscolex caudatuswas not found in cattle. These data indicate that the ciliate faunas of cattle and sheep in this Western Canadian environment are similar to those found in Japan.Key words: ciliate population, rumen, cattle, sheep.

ISSN:0008-4166    

DOI:10.1139/m89-112

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Inoculation of wheat seedings withAzospirillum brasilenseCd increased proton efflux from the roots. Inoculation of seeds or young seedlings using bacterial cultures at the logarithmic phase of growth caused the strongest proton extrusion. The increased effect lasted up to 20 h. No difference was detected between inoculated and noninoculated plants 20 h after inoculation. Both inoculated and noninoculated plants decreased the final pH of the nutrient solution to 3.2 and had an average proton extrusion of 4.3 μmol H+ ∙ (g fresh weight)−1∙h−1.Azospirillum brasilenseCd inoculation of wheat roots in which proton efflux was inhibited by the addition of either nitrate, dicyclohexylcarbodiimide, or orthovanadate resulted in partial recovery of proton efflux activity in these roots. Inoculation of wheat seedlings also changed the regular pattern of root proton efflux over prolonged periods of time. It is suggested thatA.brasilenseCd inoculation influenced membrane activity and subsequent proton efflux in roots of wheat seedlings.Key words:Azospirillum, plant–bacteria interaction, proton efflux, rhizosphere bacteria,Triticum aestivum, wh

ISSN:0008-4166    

DOI:10.1139/m89-113

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Characterization and enumeration of the adherent epimural community of the rumen wall of young, conventionally reared lambs were carried out from 2 to 21 days after birth. Three hundred strains were isolated by anaerobic procedures from three sites: dorsal, ventral, and caudal sacs, and from the sloughed epithelial cells. The population of epimural bacteria was very dense from the first days of the lamb's life. This population increased slightly with age. During the first week the counts were similar in the dorsal and ventral sacs, but they were 10 to 100 times lower in the caudal sac. Total counts for anaerobic bacteria were higher than the counts for aerobic bacteria. The isolated strains were distributed into 19 groups: 11 groups included aerotolerant strains, and 8 others, strictly anaerobic strains. During the first week the facultative microflora was mainly composed ofEscherichia coliandStreptococci. Later, the epimural community was more complex and includedStaphyloccus,Micrococcus, andGaffkya. The strictly anaerobic microflora was mainly composed ofClostridium,Peptostreptococcus,Veillonella,Propionibacterium, andAcidaminococcus. Some of these strains appeared to be similar to those previously isolated from the rumen fluid of young lambs; however, the generaMicrococcus,Veillonella,Gaffkya, andAcidaminococcus, andE.coliseemed to be specific of the rumen wall tissues.Key words: rumen, lamb, microflora, rumen wall.

ISSN:0008-4166    

DOI:10.1139/m89-114

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Developments of bacterial and phytoplankton biomass were assessed during an annual sampling cycle in a eutrophic lake (Lake Aydat, France). Bacterial abundance, estimated by epifluorescence microscopy counting, varied from 0.61 to 12.72 × 106cells/mL, confirming the eutrophic status attributed to this lake. Cellular densities were nearly homogeneously distributed in the water column. Mean values for bacterial abundance, obtained from three sampling depths (2, 7, and 14 m) were 3.70, 4.23, and 3.66 × 106cells/mL. In the epilimnion, phytoplankton productivity and community composition, as well as temperature, appeared to control bacterial development. Bacterial biomass varied from 0.5 to 43.5 × 10−2 mg C/L. Mean values for the three sampling depths were 8.1, 10.1, and 9.1 × 10−2 mg C/L. Although bacterial biomass was significantly correlated with bacterial abundance, only 45 to 65% of its variation could be explained by abundance. Individual cell biovolumes varied up to sixfold, from 0.014 μm3in spring and autumn to 0.090 μm3in summer. The largest bacterial cells and the most elevated bacterial biomass were reached when bacteria were attached to phytoplankton or detrital organic matter, primarily during summer. Mucilaginous phytoplankton, such asGomphosphaeriaandSphaerocystis, was found to be particularly good substrate available for the development of large and attached bacteria.Key words: eutrophic lake, bacterioplankton, phytoplankton, seasonal coupling, bacterial attachment.

ISSN:0008-4166    

DOI:10.1139/m89-115

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

Under aerobic conditions, ethylene production and oxidation occurred simultaneously in organic and mineral horizons of a northern hardwood forest. Ethylene oxidation rates in mineral soil were high (up to 25 nmol∙g−1∙day−1) relative to other forest soils, and exceeded production rates unless moisture contents were raised above saturation. Acetylene inhibits ethylene oxidation while allowing ethylene production to proceed; control samples for acetylene reduction assays should therefore contain acetylene plus a nitrogenase inhibitor such as carbon monoxide if forest soil nitrogenase activity is to be accurately quantified. A level of 7 kPa carbon monoxide gave complete nitrogenase inhibition in active forest floor samples in the presence of acetylene; carbon monoxide was applied 2 h in advance of acetylene to compensate for its lower solubility in water. Use of this methodology revealed a strong inhibitory effect of saturated water contents on forest floor acetylene reduction activity, suggesting that aerobic N2-fixing activity predominated in unamended forest soil samples.Key words: nitrogenase, acetylene reduction, ethylene formation, forest s

ISSN:0008-4166    

DOI:10.1139/m89-116

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

This report describes the purification and partial characterization of a cytotonic enterotoxin produced by a human diarrheal isolate (SSU) ofAeromonas hydrophila. The extracellular enterotoxin was purified by (NH4)2SO4precipitation, hydrophobic column chromatography, and chromatofocusing. The highly purified enterotoxin exhibited a molecular mass of 44 kDa and an isoelectric point in the range of 4.3–5.5 as determined by chromatofocusing. Western blot analysis usingAeromonasanti-enterotoxin revealed a single band at 44 kDa; however, cholera antitoxin failed to detect the enterotoxin antigen. This non-cholera toxin cross-reactive (non-CTC) enterotoxin was biologically activein vivoas determined by rabbit ligated ileal loop and rabbit skin vascular permeability assays. Biological activity also was expressedin vitroby this toxin as measured by the elongation of Chinese hamster ovary (CHO) cells. The enterotoxic activity associated with this molecule was neutralized completely by homologous antibodies but not by cholera antitoxin. The purified toxin preparation was free of hemolytic and cytotoxic activities as determined by its inability to lyse rabbit red blood cells or damage CHO cells, respectively. Furthermore, this toxin induced the elevation of cAMP in CHO cells suggesting thereby that the mechanism of action ofAeromonasnon-CTC enterotoxin may be similar to heat-labile enterotoxins ofEscherichia coliandVibrio cholerae.Key words:Aeromonas hydrophila, cytotonic enterotoxin, cholera toxin, cAMP

ISSN:0008-4166    

DOI:10.1139/m89-117

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

A black fungus isolated from oak bark was identified as a member of the yeast-like genusPhaeococcomyces. While no sexual reproduction was observed, the isolate showed characteristics associated with basidiomycetous yeasts: it was non-fermentative, produced extracellular urease, was positive with the diazonium blue B colony colour test, and had an enteroblastic form of budding. The isolate produced a black pigment constitutively which was shown to be a melanin. Production of the pigment was inhibited by the incorporation of low levels of the fungicide tricyclazole in growth media, inidicating that it was a pentaketide melanin. Pigmentation mutants were produced. Albino mutants did not produce melanin. Diffusion mutants accumulated the pentaketide melanin pathway oxidation products flaviolin and 2-hydroxyjuglone in culture media. Cross-feeder mutants accumulated scytalone, a pentaketide melanin pathway intermediate, in culture media, and caused albino mutants to melanize when grown in proximity to them on agar plates. A single mutant was isolated which excreted 1,8-dihydroxy naphthalene, the end product of the pathway. Broth cultures ofPhaeococcomycessp. in stationary growth phase released melanin in the form of granules, with an average diameter of 30 nm.Key words: black yeast, melanin production,Phaeococcomycessp.

ISSN:0008-4166    

DOI:10.1139/m89-118

出版商:NRC Research Press    

年代:1989

数据来源: NRC

摘要:

The presence of O antigen of the lipopolysaccharide onKlebsiella pneumoniaeis responsible for the low transformation frequencies observed. No significant influence of capsular polysaccharide could be observed. This phenomenon was independent of the transformation procedure and plasmid size.Key words: lipopolysaccharide, capsular polysaccharide, transformation,Klebsiella pneumoniae.

ISSN:0008-4166    

DOI:10.1139/m89-119

出版商:NRC Research Press    

年代:1989

数据来源: NRC