摘要:

The effect of temperature on the succinate transport system was studied in the arcticRhizobiumstrain N31 (isolated fromAstragalus alpinus) and in the temperate strain SM2 (isolated fromOnobrychis viciifolia). Only one inducible succinate transport system was found in the two strains as indicated by the linear Eadie–Hofstee plot obtained at 10, 15, and 25 °C. The transport of succinate was not affected by arsenate, but was inhibited by carbonyl cyanidem-chlorophenylhydrazone, KCN, and iodoacetate, implying an active process, a proton motive force, and essential sulfhydryl groups in the system. At 25 °C the apparentKmandVmaxvalues observed were 6.7 and 7.4 μM and 40.8 and 27.9 nmol∙min−1∙mg protein−1for strains N31 and SM2, respectively. Similar kinetic parameters for succinate transport at 25 °C were obtained with the cells of both strains grown at 10 or 25 °C. However, when transport was measured at 10 °C theKmandVmaxvalues obtained with strain SM2 were higher for cells cultured at 10 °C than for those cultured at 25 °C, suggesting that this temperate strain might be more affected by low growth temperature than the arctic strain N31. The succinate transport systems in the two strains were affected by temperature in a similar fashion, as indicated by similar Arrhenius plots ofVmaxshowing a discontinuity at 20 °C and by comparable apparent energy of activation values. These observations suggest that the cold adaptation of strain N31 is not related to a cold adaptation of the succinate carrier.Key words: arctic,Rhizobium, succinate, symbiosis, transp

ISSN:0008-4166    

DOI:10.1139/m93-138

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

MostButyrivibriostrains have been isolated from the gastrointestinal tract of animals and have been classified asButyrivibrio fibrisolvens. A few strains isolated from human feces are designated asButyrivibrio crossatus, the other species in this genus.Butyrivibrio fibrisolvensstrains are anaerobic, curved rods that produce butyrate, but numerous studies have shown that these strains display considerable variations in phenotypic properties and heterogeneity in DNA relatedness. Although over 60 strains have been characterized in these respects, the cell wall structure of only a few strains has been studied. In this study, cell wall related properties of 12 strains representative of five DNA relatedness groups were examined. All strains were very sensitive to penicillin and other antibiotics that interfere with cell wall synthesis. Although an occasional resistant strain was found, most strains were sensitive to a variety of protein synthesis antibiotics that included aminoglycosides and tetracycline. In contrast, all strains were highly resistant to nalidixic acid. Peptidoglycans were isolated from sevenB.fibrisolvensstrains andLachnospira multiparus. Compositional analyses indicated molar ratios of 0.7:2:2:1:0.8 for muramic acid, glucosamine, alanine, glutamic acid, and diaminopimelic acid, respectively, in all peptidoglycans, which also showed a low degree of cross-linking. A trichloroacetic acid extractable galactosamine-containing polysaccharide copurified with theButyrivibriopeptidoglycans. Electron microscopy of thin sections showed all strains to possess a Gram-positive type of cell wall that was atypically thin (12–18 nm). Most strains also displayed external (surface) polysaccharide layers. Cytoplasmic inclusions and granules were evident in many strains and were composed of polysaccharides, on the basis of cell composition analyses. The findings thatButyrivibriostrains have overall similarities in cell wall properties, but differences in DNA relatedness, suggest that these organisms should be classified as several more species in the same genus or family.Key words:Butyrivibrio fibrisolvens,Butyrivibrio crossatus, cell wall, peptidoglycan, ruminal bacteria.

ISSN:0008-4166    

DOI:10.1139/m93-139

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The chemotactic response of four common soil bacteria,Agrobacterium radiobacter,Bacillus subtilis,Pseudomonas fluorescens, andXanthomonas malvacearum, was observed in natural soil to conidia ofCochliobolus sativus, chlamydospores ofFusarium oxysporumf.sp.ciceri, sclerotia ofMacrophomina phaseolina, and oospores ofPhytophthora drechslerif.sp.cajani. All bacteria migrated through soil toward fungal spores. Chemical analysis of fungal exudates demonstrated the presence of various amino acids and sugars that served as chemoattractants. The effect of temperature, pH, soil water matric potential, and soil texture on bacterial chemotaxis toward fungal spores was also investigated. In general, the response of bacteria to different types of fungal spores was significantly greater (P = 0.05) at higher water matric potential (0 and −5 kPa) than at lower soil water potential (−10 and −20 kPa). The chemotactic response was greatest in sandy soil, followed by sandy loam and clay loam soil. High temperature (40 °C) was not favourable for bacterial chemotaxis. The chemotactic response decreased by 4 to 28 times when soil pH decreased from 7 to 5 or increased from 7 to 9. The relative concentration response of the exudate of fungal spores and the motility or chemotaxis of bacteria were assessed. A significant positive correlation (P = 0.05;r = 0.89–0.92) was recorded between motility and relative concentrations of exudate. The swimming speed and tumbling frequency ofPseudomonas fluorescenscells was observed at different pH values and temperatures. The swimming speed of bacteria increased with increasing temperature, but decreased with an increase in pH from 5 to 7. The tumbling frequency had a sharp peak at 30 °C and pH 7. Bacteria were able to stimulate the release of exudate from the fungal spores. The amount of exudation was also affected by temperature, pH, and soil texture. A positive significant correlation (P = 0.05;r = 0.79–0.85) was recorded between exudation and a progressive increase in temperature. The amount of exudation also increased with an increase in soil pH from 5 to 8, but further increases in pH decreased the rate of exudation. In general, fungal spores exuded the greatest amounts of carbon compounds in sandy soil, followed by sandy loam and clay loam soil. Exudation in sandy soil was often greatest in the presence ofA.radiobactercells, while the greatest exudation in sandy loam and clay loam soils was induced byB.subtiliscells.Key words: chemotaxis, chemoattractants, fungal spores, motility.

ISSN:0008-4166    

DOI:10.1139/m93-140

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The growth properties of cell lines derived fromSpodoptera frugiperda(alfalfa looper) andChoristoneura fumiferana(spruce budworm) were investigated. The data demonstrated that the spruce bud worm cell line grew more slowly than the alfalfa looper cell line, and this reduced growth rate appeared to affect the rate of baculovirus replication in infected cells. Trypsinizing the spruce budworm cells or varying the multiplicity of infection did not greatly influence the rate of viral replication.Autographa californicanuclear polyhedrosis virus was able to replicate its DNA and synthesize late and very late proteins in both cell lines but did not produce infectious extracellular virus in the spruce budworm cell line. The replication cycle ofC.fumiferananuclear polyhedrosis virus did not produce late proteins or infectious extracellular virus in the alfalfa looper cells. The results indicate thatS.frugiperdacells are nonpermissive for theC.fumiferananuclear polyhedrosis virus butC.fumiferanacells are semipermissive for theA.californicanuclear polyhedrosis virus, resulting in an abortive infection.Key words: baculovirus, host specificity, AcMNPV, CfMNPV, spruce budworm.

ISSN:0008-4166    

DOI:10.1139/m93-141

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Phosphorus solubilizing microorganisms constituted 26 to 46% of the microbial population of the four Quebec soils studied. Among the microorganisms isolated 10 bacteria and 3 fungi were selected for their ability to form a large clarification zone on solid media containing different insoluble P salts. In a glasshouse assay, the inoculation of maize seeds with the 13 organisms selected did not significantly influence maize growth or P content, after 3 weeks of growth. In field trials, theEnterobactersp. isolates 22aand 22cand thePseudomonassp. isolate 24 significantly increased (7–9%) plant height after 60 days of growth. After 108 days of growth, only isolate 22ccaused a significant increase (23%) of shoots fresh mass. Field trials with Paris Island Cos lettuce seeds inoculated with the bacterial isolates 22aand 24 resulted in 14 and 18% increase in shoots fresh mass yields, respectively. Isolate 68 ofRhizopussp. also increased lettuce yield by 11% over the control. The growth improvement observed in maize and lettuce probably did not result only from P solubilization activity but also, in part, from the ability of the four organisms inoculated to produce siderophores and auxins.Key words: microbial solubilization, phosphorus, corn, lettuce.

ISSN:0008-4166    

DOI:10.1139/m93-142

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Phytopathogenic strains ofPseudomonas syringaehave different physiological properties in their different growth phases. Screening of four strains at the cellular level revealed that the sensitivity ofP.syringaeto oxidative stress, heat, and selected antibiotics is correlated with the growth phase and enzyme properties and is affected by the composition of the nutrient environment. The interrelation of responses to different stresses allows the conclusion to be made that coordinated stress response regulation occurs in some strains ofP.syringae. This is important for studies that involve plant–bacteria associations in which the microbes have to cope with complex stress situations. It further opens an avenue of screening at the molecular level for stress response regulons in fluorescent pseudomonads.Key words:Pseudomonas syringae, antibiotics, catalase, growth phase, stress.

ISSN:0008-4166    

DOI:10.1139/m93-143

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

We report here an extensive examination of the ploidy of a basidiomycetous yeast. The ploidy of 34 strains ofCryptococcus neoformansvar.neoformans, isolated mostly from Japanese patients, was determined by means of quantitative fluorescence microscopy after DNA staining with propidium iodide. The sexual characteristics of the strains including the two tester strains were as follows. Twenty-four strains were of the heterothallic α type, 1 was of the heterothallicatype, and 2 were self fertile; the remaining 7 showed no sexual response. The following strains were found to be haploid: the heterothallicastrain, 20 of the 24 heterothallic α strains, and 3 of the 7 asexual strains. Thus, theC.neoformansstrains were mostly haploid, as the sexual response of this organism suggests. Both of the self-fertile strains and four of the seven asexual strains were diploid. Unexpectedly, 4 of the 24 heterothallic α strains were diploid.Key words: ploidy, heterothallic diploid,Cryptococcus neoformans, basidiomycetous yeast, mating.

ISSN:0008-4166    

DOI:10.1139/m93-144

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Strains ofActinoplanesspp. were evaluated for their in vitro parasitism of oospores ofPythium aphanidermatum,Pythium arrhenomanes,Pythium irregulare,Pythium myriotylum, andPythium ultimum. Oospores ofPythium arrhenomanes,Pythium irregulare, andPythium myriotylumwere identified for the first time as hosts ofActinoplanesspp. Newly recorded parasites of oospores ofPythiumspp. wereActinoplanes azureus,Actinoplanes brasiliensis,Actinoplanes caeruleus,Actinoplanes ferrugineus,Actinoplanes ianthinogenes,Actinoplanes italicus,Actinoplanes minutisporangius,Actinoplanes rectilineatus,Actinoplanes teichomyceticus,Actinoplanes utahensis,Actinoplanes violaceous,Actinoplanes yunnahenis, plus 15 strains ofActinoplanesyet to be speciated. Parasitized oospores had disorganized cytoplasms and hyphae ofActinoplanessp. emerging from them. Infection of oospores in vitro varied from 0 to > 90%. Strains also were very active parasites of oospores in sterile soils. When added to nonsterile soils, several strains increased (p = 0.05) the level of oospore parasitism compared with nonsupplemented soils. Strains ofActinoplanesspp. exhibited a host specificity for species ofPythiumin vitro and in soil. Sporulation ofActinoplanessp. from infected oospores incubated on soil was frequent and more abundant than that observed in vitro.Key words:Pythiumspp.,Actinoplanesspp., actinomycetes, biological control, host–parasite specificity.

ISSN:0008-4166    

DOI:10.1139/m93-145

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Yeasts and coliform bacteria were isolated from water that accumulated in the central cups and adjacent leaf axilae of two bromeliads,Neoregelia cruentaof a coastal sand dune andQuesnelia quesnelianaof a mangrove ecosystem near the city of Rio de Janeiro, Brazil. The mean total coliform counts were above 10 000 per 100 mL for waters of both plants, but the mean fecal coliform counts were only 74 per 100 mL forQ.quesnelianaand mostly undetected in water fromN.cruenta. Of 90 fecal coliform isolates, 51 were typical ofEscherichia coliin colony morphology and indol, methyl red, Volges–Proskauer, and citrate (IMViC) tests. Seven representatives of the typicalE.colicultures were identified as this species, but the identifications of nine other coliform bacteria were mostly dubious. The yeast community ofN.cruentawas typical of plant surfaces with basidiomycetous yeasts anamorphs, and the black yeastAureobasidium pullulanswas prevalent.Quesnelia quesnelianahad a substantial proportion of ascomycetous yeasts and their anamorphs, including a probable new biotype ofSaccharomyces unisporus. Our results suggested that the microbial communities in bromeliad waters are typically autochtonous and not contaminants.Key words: yeasts, fecal coliforms, bromeliad waters, mangrove, Restinga.

ISSN:0008-4166    

DOI:10.1139/m93-146

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A thermophilicRhizopus oryzaewas isolated, and parameters affecting its production of extra- and intra-cellular lipases were investigated. All carbon sources tested with the exception of sucrose generally inhibited the production of extracellular lipase, but enhanced the production of intracellular lipase. Peptone was the best substrate for extracellular enzyme production, but for intracellular lipase production other substrates such as tryptone, tryptic soy digest, polypeptone, and corn steep liquor gave comparable results. Among lipid substrates, glycerol was the only stimulator of extracellular enzyme production, whereas olive oil, triolein, and oleic acid had very positive effects on intracellular enzyme production. Shaking enhanced the production of both types of enzymes; the temperature optima were 45 and 37 °C for extra- and intra-cellular lipases, respectively. A pH of 5.0 was optimal for production of both enzymes.Key words: lipases,Rhizopus oryzae, production.

ISSN:0008-4166    

DOI:10.1139/m93-147

出版商:NRC Research Press    

年代:1993

数据来源: NRC