摘要:

Bacterial cell walls and their structural units, particularly peptidoglycan, induce a vast variety of biological effects in host organisms. The pathobiological effects of peptidoglycan are greatly enhanced by various modifications and substitutions to its basic composition and structure. One such modification is the presence of acetyl moieties at theC-6 hydroxyl group ofN-acetylmuramyl residues, and to date, 11 species of eubacteria, including some important human pathogens, such asNeisseria gonorrhoeae,Proteus mirabilis, andStaphylococcus aureus, are known to possessO-acetylated peptidoglycan. This review addresses the influence ofO-acetylation of peptidoglycan on its resistance to degradation bothin vitroandin vivo, the clinical importance of the modification, and the currently held views on the pathway for its biosynthesis.Key words: peptidoglycan, murein,O-acetylation, lysozyme, arthritis.

ISSN:0008-4166    

DOI:10.1139/m92-014

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Eighty strains ofYersinia enterocoliticaand related species isolated from slaughtered pigs and pork products were tested for possession of virulence-associated phenotypes by employing 12 in vivo and in vitro assays. The isolates could be broadly divided into two groups: (i) strains belonging to pathogenic bioserotypes ofY.enterocoliticathat displayed virulence-associated characteristics in most or all assays and (ii) strains belonging toY.enterocoliticabiotype 1A and to related species that were largely negative in these assays. No individual test was found as a single reliable measure of virulence. All strains belonging toY.enterocoliticaserotype O: 1,2,3 were pyrazinamidase positive (indicates avirulence) and autoagglutination negative but were positive in all other virulence assays. Salt aggregation was found to be a better indicator of virulence than latex particle agglutination, both of which measure surface hydrophobicity. Overall, tissue culture cell invasion provided the best selection of a subpopulation of yersiniae that are potentially virulent. However, crystal violet and Congo red binding assays among others provided good prediction of virulence at the time of testing. Our results provide further evidence that swine may constitute an important reservoir of human pathogenic strains.Key words:Yersinia enterocolitica, virulence phenotype, human pathogen.

ISSN:0008-4166    

DOI:10.1139/m92-015

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Most media in which the growth of shaken submerged cultures ofStreptomyces akiyoshiensiswas examined did not support the formation of well-dispersed mycelial suspensions. Investigation of the culture conditions promoting dispersed growth showed the pH of the culture medium to be of critical importance; an initial value of 5.5 minimized aggregation of the mycelium while supporting adequate biomass production. In cultures started at this pH, spore inocula gave better mycelial dispersal than did vegetative inocula; with spore inocula, growth morphology was also less affected by inoculum size. The composition of the nutrient solution influenced the extent of mycelial dispersal; slow growth was often associated with clumping but no clear correlation was observed between pellet formation and the ability of carbon or nitrogen sources to support rapid growth. Increasing the phosphate concentration from 0.5 to 15 mM caused a modest decrease in mycelial aggregation. Conditions promoting a well-dispersed mycelium suitable for studying the physiological control of secondary metabolism also supported the formation of 5-hydroxy-4-oxonorvaline byS.akiyoshiensis.Key words:Streptomyces akiyoshiensis, mycelial aggregation, growth conditions.

ISSN:0008-4166    

DOI:10.1139/m92-016

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

The membrane fractions of the microaerobically grown type strains ofWolinella curva,Wolinella recta,Bacteroides ureolyticus, andBacteroides graciliscontained membrane-bound cytochromeb, cytochromec, and CO-binding cytochromec. Soluble cytochromecand CO-binding cytochromecwere also present. AlthoughB.gracilisis oxidase negative, it possessed cytochromec. With H2or formate as the electron donor, proton efflux from anaerobic cells occurred upon addition of a pulse of oxygen. With formate as the electron donor, the H+/O ratios ofW.curva,W.recta,B.ureolyticus, andB.graciliswere 0.75, 1.66, 2.06, and 2.04, respectively. With H2as the electron donor, the H+/O ratios ofW.curva,B.ureolyticus, andB.graciliswere 1.25, 1.97, and 2.36, respectively. Proton translocation was inhibited by the protonophore carbonylcyanidem-chlorophenylhydrazone. The results confirm that the organisms are not anaerobes but are microaerophiles capable of respiring with oxygen.Key words: cytochrome, proton,Wolinella,Bacteroides, microaerophile.

ISSN:0008-4166    

DOI:10.1139/m92-017

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

The epiphytic populations ofPseudomonas syringaewere monitored on 23 barley entries planted in the field in four replications during the summer of 1986, and on six selected entries during the summer of 1987, from the second-leaf stage until senescence. Populations were initially low (0–3 log colony-forming units (cfu) per leaf) in all but one entry; they generally increased throughout the season, and at the end they reached 3–7 log cfu/leaf. Significant differences among the average epiphytic populations were found in the 1986 trial; only one entry, however, had a significantly different average population in the 1987 trial. The slopes of population increase were also compared: significant differences were observed in 1986 but not in 1987. In addition to epiphytic population counts, the percentage of ice nucleation active bacteria was determined in the population isolated from each leaf sample, and averaged throughout the season for each entry. Significant differences were observed in 1986 and in 1987. When the entries were ranked according to their average epiphytic population and compared between the two experiments, they were found to be very similar. The same was not true for the other parameters studied in the experiment.Key words: epiphytic populations, ice nucleation, barley.

ISSN:0008-4166    

DOI:10.1139/m92-018

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

Treatment ofPseudomonas syringaecells with 50 μM dodecylguanidine monoacetate (dodine) resulted in the rapid degradation and release of RNA and cell lysis. Higher concentrations resulted in a progressive decrease in the intensity of these responses, and the appearance of extensive zones of coagulated cytoplasm, indicating that the decrease in RNA degradation probably resulted from an inhibition of the RNases, due to protein denaturation. Dodine also induced expansion of the outer membrane, with the formation of protuberances and intracellular myelin-like structures, which were already evident after 1 min of treatment, indicating that dodine is able to cross the outer and cytoplasmic membranes rather rapidly, and to form, alone or in combination with cell phospholipids and proteins, considerable amounts of triple-layered profiles. InP.syringaecells, saturation levels of dodine corresponded to more than five times the amount needed to form a close-packed monolayer of dodine on the cell surface. The different membranous structures formed in dodine-treated cells, and the coagulation of the cytoplasm, seem to be responsible for the uptake of such high amounts of dodine. The uptake isotherm was essentially Langmuirian. The results presented in this and previous reports indicate that the antibacterial activity of dodine onP.syringaeis mainly the result of the action of micelles of the surfactant.Key words: dodine, fungicide, surfactant,Pseudomonas syringae.

ISSN:0008-4166    

DOI:10.1139/m92-019

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

The influence of filamentous fungi isolated from petals of bean and rapeseed on white mold caused bySclerotinia sclerotiorumwas evaluated. In laboratory trials, macerates of agar plugs containing hyphal fragments of the pathogen in combination with individual fungi were applied onto celery petioles, and subsequent lesion diameters were recorded. The efficacy of 10 fungi exhibiting a spectrum of lesion suppression on celery was correlated with the efficacy of the same fungi in growth-room (r = 0.78,P = 0.005) and greenhouse (r = 0.68,P = 0.032) trials. From 315 isolates of fungi evaluated in the laboratory trials, the 10 most suppressive isolates were selected and evaluated in growth-room trials. Spores of the test fungi were applied onto flowers simultaneously with, and up to 24 h after, inoculation with ascospores ofS.sclerotiorum. The most suppressive fungi included isolates ofAlternaria alternata,Drechslerasp.,Epicoccum purpurascens,Fusarium graminearum,Fusarium heterosporum, andMyrothecium verrucaria. These fungi did not provide consistent control of white mold of bean in a field test repeated four times in 1988. However,Drechslerasp. andE.purpurascenssignificantly reduced the incidence of white mold in one and two trials, respectively. Combination treatments ofA.alternataand Benlate (1.1 kg active ingredient ha−1) suppressed white mold significantly more than either treatment alone in one of four trials.Key words:Sclerotinia sclerotiorum, biological control, fungicide interaction.

ISSN:0008-4166    

DOI:10.1139/m92-020

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

The ultrastructure of natural myxospores and glycerol-induced myxospores has been studied in fourArchangium gephyrastrains (AG3, AG5, AG9, and AG10). The induced myxospores show an oval shape, characteristic of the genusArchangium, and an electron-dense coat surrounds the cell wall. The cytoplasm contains abundant electron-lucent inclusions. Sometimes, a membranous structure appears between the coat and the outer membrane. The fruiting-body myxospores show an oval shape similar to that observed in induced myxospores, but with a slightly thicker outer coat. In many of the natural myxospores, some membranous, lamellar or vesicular structures appear. They are located between the coat and the outer membrane, resembling those that appeared in induced myxospores. These have not been previously mentioned in papers on fruiting-body myxospores. These structures occasionally seem to be fused, giving rise to membranous sacs filled with an amorphous material of medium electron density. We propose that these vesicles are formed from the waved outer membrane and from the fruiting-body matrix. Large, dense, fusiform inclusions with an internal crystalline array are frequently found in the cytoplasm of natural myxospores, and cells during differentiation, in strains AG3, AG9, and AG10.Key words:Archangium gephyra, electron microscopy, myxospores, ultrastructure.

ISSN:0008-4166    

DOI:10.1139/m92-021

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

The effects of yeast culture age, carbon source, growth temperature, and germ-tube inducers on adherence to primary fibroblast cultures was studied in conjunction with the determination of adherence-mediated mammalian cell damage by measuring chromium-51 release from fibroblast monolayers. The results indicated that yeast culture age affected adherence only when the yeasts were grown at 37 °C, not after growth at 28 °C. At 37 °C, quantitatively fewer exponential-phase, glucose- or galactose-grown yeasts adhered to fibroblasts than did yeasts that were in lag or stationary phases. The reduced adherence correlated with less chromium-51 release and reduced germ-tube formation. The addition of germ-tube inducers, such asN-acetyl-D-glucosamine or serum, to exponential-phase yeasts caused an increase in germ-tube formation with a concomitant increase in yeast adherence and release of chromium-51 from the monolayers. Exponential-phase galactose-grown yeasts were more responsive to serum-induced germ-tube formation, germ-tube elongation, and fibroblast adherence than were exponential-phase glucose-grown yeasts. In addition, exponential-phase galactose-grown yeasts caused more chromium-51 release from monolayers in the presence of serum than did glucose-grown yeasts. Overall, conditions that enhanced germ-tube formation and elongation resulted in greatest adherence-mediated damage to the monolayers.Key words:Candida albicans, fibroblasts, morphogenesis.

ISSN:0008-4166    

DOI:10.1139/m92-022

出版商:NRC Research Press    

年代:1992

数据来源: NRC

摘要:

The role of sulfide in the relief of acetylene inhibition of nitrous oxide reduction byFlexibacter canadensiswas studied. In this organism, the reversal of acetylene inhibition of nitrous oxide reduction is correlated with a 90% decrease in the dissolved sulfide concentration. The fate of this sulfide is not known, since there was no concomitant increase in acid-soluble sulfide and volatile sulfur compounds were not detectable by flame photometric gas chromatography. Of the other sulfur-containing compounds tested (sulfate, sulfite, thiosulfate, cysteine, methionine, dithionite, dithionate, and glutathione), only cysteine relieved the acetylene block of nitrous oxide reduction byF.canadensis. Under similar experimental conditions, other denitrifiers tested (Azospirillum brasilense,Pseudomonas stutzeri, and aFlavobacteriumisolate) failed to reduce nitrous oxide in the presence of sulfide and an inhibitory concentration of acetylene. It is concluded that both biological and abiological factors contribute to the sulfide relief of acetylene inhibition of nitrous oxide by pure cultures ofF.canadensis.Key words: denitrification, nitrous oxide, acetylene, sulfide,Flexibacter canadensis.

ISSN:0008-4166    

DOI:10.1139/m92-023

出版商:NRC Research Press    

年代:1992

数据来源: NRC