ISSN:0008-4166    

DOI:10.1139/m93-039

出版商:NRC Research Press    

年代:1993

数据来源: NRC

ISSN:0008-4166    

DOI:10.1139/m93-040

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The exopolysaccharides produced by six strains ofClavibacter michiganensisssp.sepedonicuswere isolated and purified by liquid chromatography. Neutral sugar composition and molecular weights were determined for each polysaccharide fraction, using gas chromatography and high-performance size-exclusion chromatography. The serological reaction of each fraction was tested using enzyme-linked immunosorbent assay. Exopolysaccharide from nonmucoid strains contained only low molecular weight polysaccharides (1.5 × 103to 1.1 × 104). Exopolysaccharide from mucoid and intermediate strains could be separated into low (4.0 × 103to 1.1 × 104) molecular weight and high (5.0 × 105to 1.6 × 106) molecular weight fractions. High molecular weight polysaccharides were composed almost exclusively of galactose, glucose, and fucose. The ratios of these sugars were highly variable among strains. Low molecular weight polysaccharides were primarily composed of galactose with significant and varying amounts of glucose, rhamnose, mannose, and ribose. All polysaccharide fractions except one, produced by a nonmucoid strain, reacted in the immunoassay test.Key words: exopolysaccharide, polysaccharide,Clavibacter,michiganensis,sepedonicus.

ISSN:0008-4166    

DOI:10.1139/m93-041

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Two Gram-negative heterotrophic marine bacterial strains had been reported not to require Na+when grown on a chemically defined medium solidifed with purified agar and prepared without added Na+. When these strains were tested in a chemically defined liquid medium they required at least 3 mM Na+for growth. The agar used in the plating medium was found to contribute 3.3 mM Na+. Increasing the concentrations of Na+in the liquid medium above 3 mM increased the rate and extent of growth of both organisms and decreased the lag periods. Optimal Na+concentrations for growth varied from 100 to 500 mM depending on the organism and the carbon source in the medium. Na+was also required for the transport of the carbon source into the cells. For the maximal rate of transport ofL-glutamate, one organism required only 10 mM Na+, the other, 50 mM. For acetate and succinate transport the optimal Na+concentrations varied from 30 to 200 mM depending on the substrate and the organism. When the initial rate of transport of glutamate into one of the organisms was plotted against Na+concentration the reponse curve was sigmoid and a Hill plot of the data indicated that the transport protein may possess three binding sites for Na+. Evidence was obtained indicating that both organisms possess a Na+-stimulated NADH oxidase. The results indicate that there are marine bacteria that grow to a limited extent at appreciably lower concentrations of Na+than have been realized previously and for these a much more definitive examination of the requirement for Na+is necessary.Key words: marine bacteria, Na+requirement, growth, membrane transport, NADH oxidase.

ISSN:0008-4166    

DOI:10.1139/m93-042

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Polyamines of various genera of the classProteobacteriawere analyzed by high-performance liquid chromatography to determine if they can serve as taxonomic markers. The major polyamine ofZymomonaswas homospermidine, whereas theAcetobacter–Gluconobactercomplex contained spermidine, suggesting the presence of two different polyamine distribution patterns in the alpha subclass. Both the homospermidine-dominant type and the spermidine-dominant type were found in heterogeneousSphingomonasspecies. Typical species belonging to the gamma subclass have their own unique polyamine pattern inXanthomonas(spermidine),Azomonas(putrescine),Frateuria(spermidine),Alteromonas(putrescine–spermidine or spermidine),Shewanella(putrescine),Marinomonas(putrescine–spermidine or spermidine),Halomonas(putrescine–spermidine or spermidine), andDeleya(spermidine). Cadaverine was sporadically distributed in some species in these genera. Some strains classified intoRhizobacter,Zoogloea,Azomonas, orAlteromonascontained 2-hydroxyputrescine found exclusively in the beta subclass. Polyamine distribution patterns are genus- and (or) species-specific and can serve as a phenotypic marker in the chemotaxonomy of theProteobacteria.Key words: polyamine, chemotaxonomy,Proteobacteria.

ISSN:0008-4166    

DOI:10.1139/m93-043

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The sensitivity of seven extremely halophilic archaeal protein synthesis systems to 42 inhibitors with different domain (kingdom), functional, and structural specificity has been studied. The results obtained underline the functional variability of archaeal ribosomes when compared with bacterial and eukaryotic reference systems. Halophilic ribosomes are sensitive to some of the specific inhibitors of bacteria, such as thiostrepton, carbomycin A, and griseoviridin, or of eukaryotes, such as anisomycin and bruceantin, and extremely sensitive to some of the universal inhibitors, such as puromycin and sparsomycin. Suitable control experiments allow us to postulate that some negative inhibitory results may be caused by competition between positively charged antibiotics and the high ionic conditions required for halophilic protein synthesis.Key words: protein synthesis inhibitors, halophilic archaea, ribosomes.

ISSN:0008-4166    

DOI:10.1139/m93-044

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A chitinase, purified to homogeneity from ethylene-treated bean leaves, was applied to actively growing mycelial cells ofRhizoctonia solanito evaluate a potential antifungal activity. Light microscopic investigations at 30-min intervals following enzyme exposure revealed the induction of morphological changes such as swelling of hyphal tips and hyphal distortions. More precise information concerning fungal cell alteration was obtained by ultrastructural observation and cytochemical detection of chitin distribution in fungal cell walls. Chitin breakdown was found to be an early event preceding wall disruption and cytoplasm leakage. The large amounts of chitin present in the walls of controlR.solanicells and the rapid chitin hydrolysis upon chitinase treatment lead us to suggest that this polysaccharide is one of the main components of this fungal cell wall and is readily accessible to chitinase, especially in the apical zone. By 60 min after enzyme treatment, labeled molecules were observed in the vicinity of some fungal cells, suggesting the release of chitin oligosaccharides from fungal cell walls. The antifungal activity of the bean chitinase on cells ofR.solanigrown in culture is discussed in relation to the potential of genetically modified transgenic plants to resist attack byR.solanithrough an antimicrobial activityin planta.Key words: gold labeling, wheat germ agglutinin, cytochemistry,Rhizoctonia solani, bean endochitinase.

ISSN:0008-4166    

DOI:10.1139/m93-045

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The adherence of the plant growth promoting rhizopseudomonadsPseudomonas aeruginosa7NSK2 andPseudomonas fluorescensANP15 to canola roots (Brassica campestrisL. c.v. Tobin) was examined by means of a bacterial bioluminescence system. The bioluminescence broad host range vector pDLUX-I was constructed from pLAFR-I and thelux A–Egenes ofVibrio fischerii. This vector was conjugally transferred into the plant growth promoting rhizopseudomonads 7NSK2 and ANP15. The transformed strains were constitutively bioluminescent at an optimal temperature of 21 °C. The measured bioluminescence was directly proportional to the density of the bacteria in suspension and was the same for both planktonic and sessile bacteria adhering to the root surface. The adherence of the plant growth promoting rhizopseudomonads was proportional to the density of the bacterial inoculum, approached saturation at 60 min, and was reversible. The kinetics of the microbial adhesion was described by a Freundlich isotherm suggesting that the adherence of the bacteria to the canola root surface does not involve specific receptors. We conclude that the pDLUX-I vector is an easy and accurate way to study the kinetics of microbial adherence to the rhizoplane.Key words: rhizopseudomonads, bioluminescence, adhesion, plant growth promotion.not available

ISSN:0008-4166    

DOI:10.1139/m93-046

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The ability to colonize the rhizosphere is essential for bacteria to function as biological control agents for soil-borne plant pathogens. Eight bacterial strains reported to colonize wheat roots, inhibit root pathogens, and (or) improve wheat growth and yield were applied to wheat seeds that were planted in fumigated and nonfumigated soil in the 1990 and 1991 growing seasons at two locations in Arkansas. Rhizosphere population sizes were highly correlated with population sizes on seeds.Bacillus subtilisstrain D-39Sr colonized roots as well in nonfumigated as in fumigated soil, and the other seven strains had rhizosphere populations 0.3 to 1.1 log units higher in fumigated soil.Pseudomonas fluorescensstrain 2-79R was one of the best colonizers, andStreptomycesstrain D-185S was the poorest. The greatest difference among strains was for relative colonization ability of crown roots in the spring. All strains exceptStreptomycesstrain D-185S appear to have broad adaptation to colonize wheat roots and are able to compete with soil microflora for colonization sites. This research indicates that it is possible to select bacteria in the generaBacillus,Pseudomonas, orXanthomonasthat will colonize roots well over diverse environments. Rhizosphere colonization by these strains was not associated with disease suppression or enhanced plant growth or yield.Key words: biological control, rhizosphere competence, wheat,Triticum aestivum.

ISSN:0008-4166    

DOI:10.1139/m93-047

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The synthesis of endoglucanase by young induced mycelia ofTrichoderma reeseiQM 9414 incubated in the presence of 1 mM sophorose (a potent cellulase inducer) was stimulated or repressed by additions of dibutyryl cyclic AMP (dBcAMP), depending on the concentration. At low concentrations (10−6and 10−5 M), dBcAMP stimulated the formation of endoglucanase; higher concentrations of dBcAMP (10−3and 10−2 M) repressed the synthesis of endoglucanase. Addition of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) at 1 and 10 μM concentrations to young induced mycelia caused an increase in intracellular cAMP and stimulated the production of endoglucanase. Neither exogenous dBcAMP nor IBMX was capable of inducing endoglucanase synthesis by itself, and neither was able to relieve catabolite repression of endoglucanase synthesis caused by glucose. All of the monosaccharides tested caused a more or less transient increase in intracellular cAMP. However, the effect of these treatments on endoglucanase synthesis was varied. The phosphorylable hexoses, both metabolizable and nonmetabolizable, increased the intracellular level of glucose-6-phosphate or its analogs and repressed endoglucanase synthesis. Nonphosphorylable sugars, such as 6-deoxyglucose, xylose,L-fucose, and (or)L-sorbose, did not influence the glucose-6-phosphate level and stimulated endoglucanase production to varying degrees. It is concluded that both cAMP and glucose-6-phosphate are involved in regulating cellulase synthesis inT.reesei. However, these factors seem to act in opposing directions.Key words: endoglucanase, induction, catabolite repression, metabolic regulation, glucose-6-phosphate, cyclic AMP,Trichoderma reesei.

ISSN:0008-4166    

DOI:10.1139/m93-048

出版商:NRC Research Press    

年代:1993

数据来源: NRC