ISSN:0008-4166    

DOI:10.1139/m85-183

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Addition of 10−2 ML-cysteine,L-cystine, orS-ethyl-L-cysteine to a synthetic medium containing xylose as the sole carbon source did not decrease ochratoxin production byAspergillus ochraceus. At that concentration,DL-homocysteine thiolactone HCl,DL-cysteine HCl,L-ethionine,S-methyl-L-cysteine, and glutathione (reduced) strongly inhibited ochratoxin production.DL-Homocysteine thiolactone HCl,DL-cysteine HCl, andL-ethionine also strongly inhibited fungal growth. At lower concentrations (10−3and 10−4 M) onlyL-ethionine decreased the toxin production. Ochratoxin inhibition caused byDL-homocysteine thiolactone HCl,DL-cysteine HCl, and glutathione was observed only in cases where the pH of the media was below 5.0. The inhibition caused by 10−3 Methionine was partially prevented by the addition of 10−3 Mmethionine but this was not the case after the addition ofS-methyl-L-cysteine to the medium.

ISSN:0008-4166    

DOI:10.1139/m85-184

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The influence of inoculum size and cell culture density on virus titer by cytopathic effect or plaque assay was studied using poliovirus type 1 and BGM (Buffalo green monkey) cells as a model for this evaluation. With a plaque assay system, a linear relationship was observed for an inoculum size of up 1 mL/25 cm2; a marked decrease in the number of plaques was observed when over 1 mL of sample was inoculated on this surface area. Cell culture density also affected virus titer; maximal titers were observed when cells were seeded at 25 000 to 75 000 cells/mL and incubated for 6 days before infection with the virus. Viral density, evaluated as most-probable-number and measured by cytopathic effect under liquid overlay, revealed that the viral titer was similar up to 1 mL inoculum and increased only when over 1 mL was inoculated. Cell density had no significant effect on the viral titer measured by the most-probable-number method and cytopathic effect. Inactivation of inoculum due to an incubation temperature of 37 °C for a short period was shown to be minimal for poliovirus type 1, reovirus type 2, coxsackievirus B-5, and the simian rotavirus SA-11. Longer inactivation time led to a 2 logs reduction of the infectious titer of coxsackievirus B-5 (in 48 h) while the other viruses showed a significant reduction in titer only after 96 h.

ISSN:0008-4166    

DOI:10.1139/m85-185

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Parental strains ofSalmonella typhimuriumhaving a specificpyrgene (pyrC,pyrD, orpyrE) fused to the structural genes of thelacoperon through the specialized transducing phage Mu dl (ApRlac) were used to construct thermostable derivatives for purposes of conducting a genetic and biochemical characterization of the individualpyrgenes. The direction of transcription of eachpyrgene in relation to the current linkage map was defined with bothpyrCandpyrEbeing transcribed counterclockwise andpyrDexhibiting clockwise transcription. Mutants displaying increasedpyrgene expression were isolated employing a genetic strategy which is of general applicability. Among the mutants, only one isolate was found to possess a mutation which was unlinked to the specificpyrgene under study; the other isolates harbored linked mutations which were inferred to becis-acting. Additional studies demonstrated that in conditions of severe pyrimidine limitation, further derepression could still occur in the mutant strains.

ISSN:0008-4166    

DOI:10.1139/m85-186

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

L-Proline dehydrogenase catalyzes the oxidation ofL-proline to Δ1-pyrroline-5-carboxylate, a reaction that is an important step in the utilization of proline as a carbon or nitrogen source by bacteria. A mutant ofEscherichia coliK-12 lackingL-leucyl-tRNA:protein transferase had been found previously to contain about five times as much proline dehydrogenase activity as its parent strain. This difference has now been shown to be due to the presence in the parent strain of a previously unrecognized mutation. This mutation, which has been designatedput-4977, specifically affects proline dehydrogenase rather than proline uptake. Although proline dehydrogenase remains inducible byL-proline in strains carrying the mutation, there is a premature cessation of differential synthesis during induction that results in a lower specific activity. The mutation shows about 50% P1-mediated cotransduction withpyrCand is therefore located at about 22 min on theE.colichromosome. Merodiploids containing a normal F′ factor still exhibit decreased enzyme activity, indicating that theput-4977mutation istrans-dominant. The mutation cannot be detected in present stocks of the transferase-deficient mutant, suggesting that this mutant is a revertant forput-4977.

ISSN:0008-4166    

DOI:10.1139/m85-187

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A number of facultatively anaerobic members of the genusBacilluswere screened for their catalase, diaminobenzidine peroxidase, and superoxide dismutase activities. A strain ofBacillus coagulans(7050) lacking peroxidatic activity and containing single catalatic and superoxide dismutase activities was selected. Responses of the superoxide dismutase activity and catalase level to the partial pressure of oxygen, and Fe and Mn levels, as well as to aerobic and fermentative metabolism, were determined. There appeared to be a relationship between high endogenous catalase levels and the high H2O2evolution and KCN insensitivity ofB.coagulansrespiration.Bacillus coagulans7050 was mutagenized withN-methyl-N′-nitro-N-nitrosoguanidine and screened for the expression of oxygen intolerance. All of the 38 stable oxygen sensitive mutants obtained had very low or completely absent catalatic activity and catalase protein. No mutant lacked superoxide dismutase, although five showed significantly lowered levels of the enzyme. Exogenous bovine liver catalase restored aerotolerance and reduced cell pleomorphism in the mutants.

ISSN:0008-4166    

DOI:10.1139/m85-188

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The properties of ATP:citrate lyase, malic enzyme, and AMP deaminase have been investigated inRhodosporidium toruloidesCBS 14. ATP:citrate lyase had a molecular size of 480 000 daltons and apparentKmfor citrate and ATP of 0.19 mMand 0.15 mM, respectively. The enzyme was inhibited by ADP, glucose 6-phosphate, palmitoyl-CoA, and oleoyl-CoA.ions showed a 95% stimulation of activity at nonsaturating concentrations (0.1 mM) of citrate. Malic enzyme had a molecular size of 205 000 daltons and an apparentKmfor malate of 0.7 mM. The enzyme was only weakly inhibited by citrate, pyruvate, oxaloacetate, and ATP but no metabolite was found which exerted a significant regulatory control over the enzyme. However this enzyme could be used as the principal, if not sole, source of NADPH needed for fatty acid biosynthesis. The role of this enzyme and the central position of malate as a key metabolite in determining how lipid accumulation could be initiated and then sustained is discussed. AMP deaminase was detected in low activities but was fourfold higher in nitrogen-limited cells. The possible role of this enzyme in degrading AMP, regulating cellular energy charge, and supplementingpools in this yeast is also discussed.

ISSN:0008-4166    

DOI:10.1139/m85-189

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Ten strains of Gram-negative, aerobic, obligately thermophilic bacteria were examined for their response to oxygen toxicity by comparing static with shaken cultures. All of the organisms tested had measurable levels of superoxide dismutase, catalase, and peroxidase. Aeration generally did not result in an increased level of superoxide dismutase in any of the thermophiles. Aeration of organisms obligate forn-alkane substrate caused an increase in cellular peroxidase levels and a corresponding decrease in catalase. The thermophiles that grew on eithern-alkanes or complex media did not grow on the hydrocarbon in aerated culture but on a complex medium, aeration effected an increased level of catalase. With the exception of a pink-pigmented thermophile which, when aerated, did not have an increased level of the three oxygen defense enzymes, most of the thermophiles surveyed had an increased level of catalase or peroxidase when exposed to increased oxygen tension. The activity of the enzymes was determined at temperatures from 25 to 65 °C and the former temperature was satisfactory for these experiments.

ISSN:0008-4166    

DOI:10.1139/m85-190

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

As with other bacteria belonging to the corynebacteria, mycobacteria, and nocardia group,Nocardiapossess in their cell walls a neutral polysaccharide. Structural analysis of the cell wall polysaccharide ofNocardia asteroidesR 399 was undertaken. The carbohydrate polymer containedD-arabinose andD-galactose as in mycobacteria. Besides these two carbohydrates we pointed out the occurrence of two additional components:D-glucose and a polyol. This polyol, because of its small amount and its uneasy detection, had been for a long time ignored. It has been proven to be the 6-deoxy-D-altritol or 1-deoxy-D-talitol. The polymer consists of a main strand composed of →5 Araf 1→ and →4Galp1→ or→5Galf1→; oligoarabinosyl side chains were localized on C3of an arabinosyl residue. Other shorter ramifications also occur on some galactosyl units. A characterization of the linkage between polysaccharide and peptidoglycan inside the cell wall has also been carried out. The two polymers are joined by a phosphodiester bond which involves 6-deoxyaltritol. As some corynebacteria previously analyzed were also shown to contain mannose (and sometimes glucose), we can conclude that the main skeleton of cell wall polysaccharides of the corynebacteria, mycobacteria, and nocardia group of bacteria is an arabinogalactan; however, individual structural features of the polysaccharide are varying according to the bacterial species. These results might be connected with variations that were observed in immunological analysis.

ISSN:0008-4166    

DOI:10.1139/m85-191

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Alkali-insoluble cellulose and water-soluble polysaccharide production by wild-typeAcetobacter xylinumcolony and liquid cultures was investigated. The mass of cellulose exceeded that of soluble polysaccharides in liquid cultures while the reverse situation occurred in colony cultures. The soluble polysaccharide fraction, 3 × 105to 5 × 105in molecular weight, was found by DEAE-Sephacel chromatography to be a complex of several acidic, nitrogenfree polysaccharides. One acidic polysaccharide was predominant in the complex, and gas–liquid chromatography and mass spectrometry showed this to contain glucose, rhamnose, mannose, and glucuronic acid in molar ratio of 6:1:1:1, respectively.13C and1H nuclear magnetic resonance spectra are presented for this major polysaccharide component. Several minor, soluble, acidic polysaccharides were related in chemical composition to the major soluble polymer. The relation of these soluble polysaccharides to cellulose biogenesis is discussed.

ISSN:0008-4166    

DOI:10.1139/m85-192

出版商:NRC Research Press    

年代:1985

数据来源: NRC