摘要:

The fungitoxic effect of increasing concentrations of elemental sulphur (S°) was studied during the pregermination period of spores ofPhomopsis viticolaand conidia ofNeurospora crassa. High concentrations of S° (> 10 μM final concentration) inhibited respiratory activities strongly and decreased the ATP content of spores and conidia. S° at low concentrations (1 and 3 μMfinal concentration) did not inhibit the respiratory activities or ATP content of spores and conidia. In spores ofP.viticola, low concentrations of S° were reduced by the cells with the production of hydrogen sulphide (H2S), principally at the level of the respiratory chain. However, in the presence of a high concentration of S°, the capacity to reduce S° increased, and was then most probably independent of the respiratory activities. Proteic and nonproteic sulphydryl groups important in cellular metabolism were probably responsible for almost all the reduction of S°. In fact, the addition of increasing concentrations of S° to spores ofP.viticolaresulted in a dramatic increase in oxidized glutathione, suggesting the participation of reduced glutathione in S° reduction. In conclusion, we suggest that the fungicidal action of S° is probably related to the oxidation of important sulphydryl groups and not to the competitive interaction between S° and oxygen at the level of the respiratory chain.Key words: elemental sulphur, fungicide, fungi,Neurospora crassa,Phomospis viticola.

ISSN:0008-4166    

DOI:10.1139/m93-107

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

35S-labelled elemental sulphur (S°) at nontoxic levels (3 μM) was incorporated into sulphur amino acids and glutathione by the spores of the fungusPhomopsis viticola. Incorporation studies were performed with 3 μM35S° during the pregermination period ofP.viticolaspores. The free sulphur amino acids and protein sulphur amino acids were purified by column and thin-layer chromatography. During the first minutes of the pregermination process of the spores, the S° was essentially metabolized into free cysteine and glutathione. Detectable concentrations of methionine and homocysteine were measured after 1 h of incubation. Azide (2 mM final concentration), an inhibitor of the mitochondrial respiratory chain at the level of cytochrome oxidase, strongly inhibited the incorporation of S°. In contrast, the uncoupler 2,4-dinitrophenol (15 μM final concentration) and sulphate did not affect the incorporation of S°. The metabolism of35S° into the protein sulphur amino acids cysteine and methionine during the germination of spores ofP.viticolaand conidia ofNeurospora crassais also discussed. It appears that S° does not necessarily have to be oxidized to sulphate prior to its incorporation into sulphur amino acids, but could be directly reduced to sulphide at the level of the respiratory chain.Key words: elemental sulphur, assimilation, sulphur amino acids,Phomopsis viticola,Neurospora crassa.

ISSN:0008-4166    

DOI:10.1139/m93-108

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

InMethanosphaera stadtmanaeproducing methane from the reduction of methanol with H2, sodium (> 0.3 mM Na+) was not required for methanogenesis or ATP synthesis. The ATPase inhibitor N,N′-dicyclohexylcarbodiimide inhibited both ATP synthesis and methanogenesis, but was only effective in the presence of low Na+(< 1 mM). The observed N,N′ -dicyclohexylcarbodiimide inhibition of methanogenesis was relieved by the addition of the protonophore 3,3′,4′,5-tetrachlorosalicylanilide. 3,3′,4′,5-Tetrachlorosalicylanilide itself caused a rapid decrease in the intracellular ATP concentration and stimulated methanogenesis. This stimulation was enhanced when the cells were incubated in the presence of NaCl. The effects of Na+on the effectiveness of N,N′-dicyclohexylcarbodiimide and 3,3′,4',5-tetrachlorosalicylanilide cannot yet be explained. Ionophores (3,3′,4′,5-tetrachlorosalicylanilide, SF6847, monensin, and gramicidin) caused decreases in the membrane potential and the intracellular ATP concentration while stimulating methanogenesis. The data presented are consistent with the coupling of the last step of methanogenesis to ATP synthesis via a proton motive force in a representative of the Methanobacteriales.Key words: methanogenesis, proton motive force, membrane potential.

ISSN:0008-4166    

DOI:10.1139/m93-109

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

A Na+-dependent active transport system for leucine has been observed inMethanosphaera stadtmanae. TheKmfor leucine as determined was 20 μM with aVmaxof 3.2 nmol∙min−1∙mg protein−1. A minimum of 5 mM Na+was required for optimal uptake rates. After correction for unspecific binding and incorporation into trichloroacetic acid precipitable materials, [14C]leucine was accumulated inside the cell to concentrations > 100 times higher than in the medium. The uptake of leucine into active cells was inhibited by the protonophore 3,3′,4′5-tetrachlorosalicylanilide but stimulated by the synthetic Na+–H+antiporter monensin. A 500 mM NaCl pulse was able to drive leucine into resting cells. Of the amino acids tested, only valine and isoleucine competed effectively with leucine for transport.Key words: archaea, archaebacteria, methanogen, leucine transport, bioenergetics, sodium motive fo

ISSN:0008-4166    

DOI:10.1139/m93-110

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

An induced phage 2204-T from an arginine-positiveLactococcus lactissubsp.lactis2204 L strain was used in transduction experiments withLactococcus lactissubsp.cremoris2204 (an arginine-negative strain containing the chloramphenicol resistance plasmid pFX3). Arginine-positive transductants were isolated at a low frequency (< 10−10arginine-positive isolates per initial recipient cell). Hybridization experiments with labelled DNA from phage 2204-T showed the presence of the temperate phage (2204-T) genome in total DNA of the transductant 2204 LT strains. No hybridization was observed with DNA from the arginine-negative strain 2204. A mitomycin C treated derivative of 2204 LT that was arginine negative also showed no hybridization, indicating that the prophage had been eliminated. The presence of the chloramphenicol resistance plasmid pFX3 in both transductants and mitomycin C cured derivatives was demonstrated by hybridization, confirming the origin of the arginine-positive isolates as derivatives of 2204.Key words: arginine metabolism,Lactococcus cremoris,Lactococcus lactis, induced phage.

ISSN:0008-4166    

DOI:10.1139/m93-111

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The toxin activity ofBordetellastrains and acellular pertussis components was evaluated in chick embryos. Eleven-day-old embryos were found to be most suitable for determination of LD50values. Eight of eightBordetella pertussisstrains possessed LD50values of 104to 106colony-forming units per dose of 100 μL. Embryos were resistant toBordetella parapertussisandBordetella bronchisepticaat doses of 1010colony-forming units. Bacterial growth did not occur in the bloodstream or tissues of the heart, kidney, brain, liver, or lungs. Pertussis toxin activity, determined by clustering of Chinese hamster ovary cells, was found in the allantoic fluid following inoculation of virulent bacteria. Purified pertussis toxin had an LD50of 1–2 μg protein/dose. Striking pathological effects of liver necrosis and oedema of the head and neck were similar following bacterial or toxin inoculation. Widespread changes occurred in the liver at the perivascular level, suggesting that after allantoic inoculation of virulentBordetellastrains, toxin is secreted, carried in the bloodstream, and causes the resultant pathology. PurifiedB.pertussislipopolysaccharide was nontoxic for embryos at doses containing 30 μg; filamentous haemagglutinin was nontoxic at doses up to 10 μg. A correlation exists between the ability of serum to neutralize killing of chick embryos by toxin and to neutralize clustering of Chinese hamster ovary cells by toxin. Although the chick embryo serum neutralization studies confirm observations of mouse intracerebral infection studies that antibody to pertussis toxin is not an absolute requirement for prevention of infection withB.pertussis, evidence is provided that anti-toxin will eliminate toxic effects owing to secretion of pertussis toxin.Key words:Bordetella, pertussis toxin, chick embryo.

ISSN:0008-4166    

DOI:10.1139/m93-112

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Approximately 80% of the genome of the prolate-headed lactococcal bacteriophage c2 was cloned into shuttle vectors pSA3 and pFX3 inEscherichia coliand transferred toLactococcus lactis. A 1.67-kilobaseEcoRV fragment containing the gene for the phage lysin was identified and the position and orientation of the phage lysin gene in the physical map of the phage were determined. The phage lysin was expressed inE.coliand its sequence was determined and compared with the sequences of other bacteriophage lytic genes. The sequence was similar, but not identical, to that of the related lactococcal phage ml3, having a number of silent substitutions and an apparent deletion that altered the carboxy terminus of the protein. Possible alternative translation initiation codons for the lysin gene and two possible alternative mechanisms for access of the lysin enzyme to the cell wall are discussed. An open reading frame upstream of the putative lysin gene was found to be 177 base pairs longer than that reported for phage ml3. A codon usage table for the lysin genes of several phages as well as for reported gene sequences fromL.lactisand lactococcal bacteriophages is presented.Key words:Lactococcus lactis, codon usage, molecular organization, holin gene.

ISSN:0008-4166    

DOI:10.1139/m93-113

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Two lytic phages, designated as H3V and R2V, specific forRhizobium leguminosarumbiovarphaseoli, were isolated and characterized. Phage H3V was active against four indigenous isolates (HURR-3, HURR-21, HURR-35, and HURR-56) and two standard strains (RCR-3605 and USDA-2669) whereas R2V was specific to one indigenous (Raj-2) and one standard (USDA-2676) strain; there was no cross infectivity. Both phages had distinct morphology; phage H3V had an oblate polyhedral head (58 × 76 nm) and a flexible noncontractile tail (120 × 10 nm), while phage R2V had a hexagonal head (56 nm wide) and a very short tail (11 × 10 nm). The lytic cycle of phage R2V requires Ca2+ions (1 mM), which considerably reduce its latent period and burst size. Adsorption and one-step growth experiments of phages revealed that H3V had a slower adsorption rate (0.56 × 10−9 cm3/min), a longer latent period (255 min), and a higher burst size (240 plaque-forming units/cell) than R2V, which had an adsorption rate of 0.94 × 10−9 cm3/min, a 210-min latent period, and a burst size of 200 plaque-forming units/cell. Inactivation of these phages by heat, osmotic shock, and uv irradiation showed that phage H3V was comparatively more sensitive than R2V. These phages were frequently detected in healthy nodules of French beans (Phaseolus vulgaris) at two different field locations and no correlation between phage titer and nodule size or colour was observed. Phage titer varied from 2.8 × 102to 1.2 × 106plaque-forming units/nodule.Key words:Rhizobium, phages, morphology.

ISSN:0008-4166    

DOI:10.1139/m93-114

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

The ruminal bacteriaFibrobacter succinogenesstrains S85 and BL2 were grown in monocultures or in coculture with strain D1 ofButyrivibrio fibrisolvens, and the solubilization of ryegrass and alfalfa cell walls (CW) and digestion of CW monosaccharides were measured.Fibrobacter succinogenesmonocultures and cocultures withB.fibrisolvensD1 degraded 58–69% of ryegrass CW, solubilizing 67–78% of CW glucose, 65–71% of CW xylose, 69–75% of hemicellulose, and 68–77% of total CW monosaccharides. When grown on alfalfa CW, those cultures degraded 28–39% of alfalfa CW, solubilizing 42–58% of CW glucose, 30–36% of CW xylose, and 37–45% of hemicellulose. With respect to both substrates,F.succinogenesstrains solubilized CW carbohydrates better than didB.fibrisolvensD1. Complementary interaction betweenB.fibrisolvensD1 and theF.succinogenesstrains was identified with respect to the utilization of some solubilized carbohydrates, but not with respect to the extent of CW solubilization, which was determined mainly by theF.succinogenesstrains. For both substrates, utilization of solubilized cellulose byF.succinogenesmonocultures was high (96–98%), whereas that of hemicellulose was lower (24–26% in ryegrass and 49–50% in alfalfa). Under scanning electron microscopy,F.succinogenesbacterial cells attached to and colonized on CW particles were characterized by the appearance of protuberant surface structures that we have identified as "polycellulosome complexes."Key words: cell wall monosaccharides, ryegrass, alfalfa, ruminal bacteria,Fibrobacter succinogenes,Butyrivibrio fibrisolvens.

ISSN:0008-4166    

DOI:10.1139/m93-115

出版商:NRC Research Press    

年代:1993

数据来源: NRC

摘要:

Cells of an aggressive, root-colonizing isolate ofPseudomonas putidaare agglutinated by a root surface glycoprotein. The agglutination phenotype inP.putidaisolate Corvallis is lacking in mutants (Agg−) derived by Tn5insertion and chemical mutagenesis. Specific mutation in theaggAlocus by Tn5insertion results in loss of agglutinability that is complemented in trans by a wild-type copy of theP.putida aggAlocus. We examined the biochemical bases of agglutination inP.putidaby comparing cell surface features in Agg+, Agg−mutants, and a genetically restoredaggAmutant. No changes in gross cell surface features involving hydrophobic or hydrophilic binding or net negative charge were observed. Three macromolecular features, pili, flagella, and lipopolysaccharide size, did not differ between Agg+and Agg−mutants. Protein profiles of cell envelope, periplasmic, and outer membrane preparations revealed pleiotropic effects of mutation in agglutination phenotype including alterations of an outer membrane protein of 47 000 molecular weight and periplasmic proteins of 56 000 and 60 000 molecular weight. The protein alterations seen in theaggA::Tn5Agg−mutant 5123 reverted to wild-type patterns upon introduction of a wild-type copy of theaggAlocus. These data suggest agglutinability may be conditioned by more than one proteinaceous component associated with the bacterial envelope layers.Key words: cell surface, binding, recognition.

ISSN:0008-4166    

DOI:10.1139/m93-116

出版商:NRC Research Press    

年代:1993

数据来源: NRC