摘要:

Listeria monocytogenesgrew between 3 and 45C. Growth at 10C was at a rate characteristic of psychrophilic bacteria. The increase in the duration of the lag phase of growth with decreasing temperatures was expressed with a hyperbolic curve which indicated an infinite lag time at 3.3C. If this relationship between lag time and temperature is a general phenomenon, it would provide a relatively rapid method for estimating minimal temperatures of growth. Initial rates for oxygen consumption during glucose metabolism and for uptake of the nonmetabolized sugar, 2-deoxyglucose, had temperature coefficients (10–30C) of about 1.5. Growth at 10C increased the rate and the capacity of 2-deoxyglucose uptake by exponential-phase cells. Uptake and incorporation ofL-leucine was relatively rapid at 10C but the temperature coefficients were greater than 2. High temperature coefficients (greater than 2.5) for nicotinamide adenine dinucleotide oxidase and lactic dehydrogenase activity in cell-free preparations indicated that the psychrotrophic properties ofL.monocytogenesdepend on the structural integrity of the cell. We suggest that the cold-resistant sugar-transport system stimulates metabolism at low temperatures by providing high concentrations of intracellular substrates.

ISSN:0008-4166    

DOI:10.1139/m72-087

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Pure cultures of the fungusMucor alternans, isolated from DDT-contaminated soils, were able to degrade DDT to water-soluble metabolites. After the addition of fungal spores to DDT-contaminated soils, however, the insecticide-degrading capacity of the fungus was no longer evident. Since under field conditions many species of fungi are simultaneously exposed to mixed residues of pesticidal chemicals, the effects of various species of soil fungi and of various insecticides on DDT degradation byM.alternanswere investigated. Experiments were conducted to study the effect of nine fungal species, their stale cell-free media, and various insecticides and related compounds on the capacity ofM.alternansto degrade14C-DDT to water-soluble metabolites. It was found that several pure fungal cultures or some cell-free media, in which mycelia had grown, could also degrade the insecticide. In most cases, however, addition of one of the various fungi to14C-DDT-treatedM.alternanscultures resulted in a total depression of the appearance of water-soluble metabolites in the media. This was due to an accumulation of the metabolites in the mycelium of the other fungus or in an inhibition of metabolite formation. Addition of stale media from various fungi to14C-DDT-treatedM.alternanscultures had various effects on fungal growth and on the capacity of the fungus to degrade the insecticide. Among the insecticides and related compounds tested only lindane, parathion, and Dyfonate caused a reduction in DDT degradation byM.alternans, without severely reducing its vegetative growth.

ISSN:0008-4166    

DOI:10.1139/m72-088

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A method is described for the separation and isolation of two electrophoretically distinct arylsulfatases (arylsulfatase EC.3.1.6.1) fromPseudomonas aeruginosa.Characterization of the enzymes revealed that they were type I arylsulfatases, with similar kinetic properties. They differed, however, in respect to charge, pH optima for substrate hydrolysis, and activation by anions. In addition, the enzymes displayed dual pH optima curves with both substrates used and the curious property of a shift in pH optima with variedp-nitrophenyl sulfate concentrations.

ISSN:0008-4166    

DOI:10.1139/m72-089

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

The enzymes involved in histidine biosynthesis and their metabolic control are similar inStaphylococcus aureusand other organisms which have been studied, although some of these enzymes inS.aureusappear to be more labile. As is true inSalmonella typhimurium, the imidazoleglycerol phosphate dehydratase ofS.aureusis inhibited in vitro by 4-amino-1,2,4-triazole (amitrole). UnlikeS.typhimurium, however, growth in the presence of amitrole does not result in derepression of the histidine biosynthetic enzymes, and as a consequence the inhibition of the growth ofS.aureusby amitrole is not overcome. This observation provided the basis for isolating mutants ofS.aureuswhich were resistant to amitrole. Most of these amitrole-resistant mutants possessed constitutively high levels of the histidine biosynthetic enzymes, and the levels of these enzymes were not repressed in most of these mutants when they were grown in excessL-histidine.

ISSN:0008-4166    

DOI:10.1139/m72-090

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Coxsackievirus (cox.) B-3 pathogenicity was markedly augmented in weanling and adult mice during a reserpine treatment. In both age groups the mortality rose to 100% after the 1st week of inoculation.In the olfactory bulb of the reserpine-treated weanling mice the score of viral lesions was 80% compared to 2% in the non-treated. In the heart of the reserpine-treated infected mice it was 62%, while it was 40% without reserpine. In the adult mice the viral tissue damage was aggravated in the interscapular brown adipose pad and the olfactory bulb. Moreover, the viral lesions in the reserpine-treated mice in both age groups showed some striking morphological differences when compared with mice injected with the virus only.The recovered virus yielded higher titers in the reserpine-treated mice in both age groups. In the adult reserpine-treated mice the LD50of the cox. B-3 recovered from the brain and heart were as high as in the weanlings.

ISSN:0008-4166    

DOI:10.1139/m72-091

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

A cell-free system which catalyzed polyuridylate-directed incorporation of (U-14C)L-phenylalanine into polyphenylalanine was obtained fromStreptomycesspecies 3022aand shown to be sensitive to chloramphenicol (CAP). Ribosomes from the CAP-producing actinomycete were of the 70-Svariety and bound the antibiotic to the same extent as ribosomes from a sensitive strain ofEscherichia coli. Chloramphenicol also inhibited protein synthesis in growing cultures ofStreptomycesspecies 3022a. The degree of inhibition was greater in non-producing than in producing cultures. In producing cultures protein synthesis was inhibited only during the early growth phase when little endogenous antibiotic had been formed. The response correlated with the sensitivity of the organism to added CAP under various growth conditions. During the lag while antibiotic resistance was developing (U-14C)L-leucine was very slowly taken up by the mycelium but no protein was synthesized. Resumption of growth was accompanied by incorporation of radioactivity into protein, but no distinctive protein could be detected when cells in the recovery phase were fractionated. Development of resistance to CAP byStreptomycesspecies 3022awas reversible, and was graded to the concentration to which the cells were exposed. The results suggest that permeability changes induced by CAP which has entered or been biosynthesized by the cell play an important role.

ISSN:0008-4166    

DOI:10.1139/m72-092

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Auxotrophic strains ofEscherichia coligenerally are motile and chemotactic in the absence of those amino acids needed for growth. Methionine auxotrophs, however, require low levels of methionine for chemotaxis. A prototroph, grown in the presence of methionine so as to repress methionine biosynthesis, also requires methionine for chemotaxis. In the absence of methionine the bacteria are still actively motile, and thus phenotypically resemble nonchemotactic mutants.A continuous supply of methionine is necessary for a normal chemotactic response, indicating the active product is labile. Under the conditions used to demonstrate chemotaxis, the major trichloroacetic acid (TCA) soluble metabolites of methionine are spermidine,S-adenosylmethionine (SAM), and a third, as yet unidentified, compound. Spermidine is readily taken up by the bacteria, but does not replace methionine for chemotaxis.S-adenosylmethionine cannot be tested directly, as it is not taken up by normal cells. However, it is rapidly turned over and thus meets the requirement for lability. The third acid-soluble compound appears to be relatively stable metabolically.

ISSN:0008-4166    

DOI:10.1139/m72-093

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Forty-two species of yeast were examined for their ability to produce enediols of the ascorbic acid class. A Roe and Kuether chromogen derived from such enediols could be isolated from 23 of the species. The chromogen from four yeasts was further identified by infrared (i.r.) spectrophotometry as being derived from ascorbic acid. At least one species from each family of yeasts was found to produce ascorbic acid.

ISSN:0008-4166    

DOI:10.1139/m72-094

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

When cells of a marine pseudomonad (ATCC 19855) were extracted with 45% aqueous phenol, lipopolysaccharide (LPS) could not be recovered from the extract. If the phenol solution used for extraction contained NaCl, KCl, and MgCl2at their concentrations in the growth medium (0.22 M, 0.01 M, and 0.026 Mrespectively) and the fluid used subsequently to dialyze the extract free of phenol was a solution of the same salts, LPS could be sedimented from the aqueous phase of the extract by centrifugation at 144 000 × g. Tests on the individual salts at their growth-medium concentrations showed that the presence of MgCl2alone in the phenol solution gave rise to even higher yields of LPS than did the three salts together. With NaCl in the phenol solution, the yield of LPS was much reduced while with KCl present, either traces or no LPS could be isolated. Qualitative and quantitative analysis of the LPS showed galactose and glucose to be the predominating neutral sugars, and glucosamine and galactosamine the major amino sugars. Two unidentified amino sugars were present in small amounts. They were tentatively identified as a 2-amino sugar with chromatographic characteristics similar to 2-aminoquinovose and a 4-amino sugar. The LPS contained 1.25% heptose sugar, 0.1% 2-keto-3-deoxyoctulosonic acid (KDO), and 12.9% lipid A.

ISSN:0008-4166    

DOI:10.1139/m72-095

出版商:NRC Research Press    

年代:1972

数据来源: NRC

摘要:

Sendai virus was concentrated from the allantoic fluid of embryonated chicken eggs by polyethyleneglycol (PEG) precipitation. A concentration of 6–8% PEG sufficed to precipitate essentially all of the virus (measured by hemagglutination) with maximum retention of cell-fusion ability. Electron-microscopic examination of the 6% PEG pellet revealed only intact virions. Thus the method is suitable for preparing Sendai virus for cell-fusion experiments.

ISSN:0008-4166    

DOI:10.1139/m72-096

出版商:NRC Research Press    

年代:1972

数据来源: NRC