摘要:

Staphylococcus aureusATCC 6538P is auxotrophic tor proline. Under conditions of proline starvation, the organism synthesizes a transport system thus greatly increasing the rate of transport of proline into the cell. The proline transport systems of both the starved and unstarved cells were shown to be enzymatic, energy dependent, and specific forL-proline. Protein synthesis was required for derepression, and when the cells were fully induced, the organism established a non-exchangeable pool for proline, whose maintenance was dependent on protein synthesis. It is proposed that this transport system serves as a scavenging mechanism when the organism is in an environment deficient in proline.

ISSN:0008-4166    

DOI:10.1139/m73-066

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Samples from dried colonies of 21 strains ofNannizziaandArthrodermawere analyzed by pyrolysis–gas–liquid chromatography. Characteristic peak patterns produced by all the strains were used as markers to correct random drift in retention time so that corresponding peaks in different pyrograms could be homologized. Variation in sample size was compensated for by comparing peaks on each pyrogram with a particular major component and scoring them simply as 0 (absent), 1 (small), or 2 (large). Proximities were calculated and analyzed for clusters by the TAXMAP procedure. The analysis always grouped replicate samples together in the same cluster. Opposite mating types of the same species were sometimes placed in the same cluster and sometimes in separate clusters. The (+) mating type ofArthroderma benhamiaewas placed in a cluster with both mating types ofNannizzia gypseaandN.obtusa, while the (−) mating type replicates ofA.benhamiaewere placed in a cluster by themselves. Finding a greater difference between pyrograms of different mating types of one species than between pyrograms of different species was unexpected and requires further investigation.

ISSN:0008-4166    

DOI:10.1139/m73-067

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Variation in the pyrochromatograms of different strains of the same species was investigated using five different isolates ofNannizzia fulvaand nine single-ascospore isolates derived from a mating of twoN.cajetanistrains. The colonies of theN.cajetaniisolates differed markedly from each other in pigmentation and texture. Their pyrograms also varied, but the variation between strains was small compared with the difference between the two species. The differences between strains were not correlated with mating type.Pyrograms of one of theN.cajetanistrains were prepared using newly packed columns. These pyrograms yielded a cluster that was somewhat distant from the otherN.cajetanistrains.

ISSN:0008-4166    

DOI:10.1139/m73-068

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Cycling of glucose at the sediment–water interface was determined through coupling measurement of natural substrate concentrations with heterotrophic uptake by the natural microbial communities in the sediment and in the water column. The same general pattern was found for both polluted and less polluted parts of Toronto Harbour, so that other labile organic species possibly have similar cycles. Velocity of uptake of glucose (flux) and turnover time showed no relationship to either substrate concentration or total organic matter of the sediments. Activity in the water column could be supported to a major extent by sediment export of substrate by turbulent diffusion. Sediment activity must be supported by particulate sedimentation and hydrolysis of large organic molecules, which may be aided by the macrobenthic community. Pollution stress apparently alters the catabolism of the substrate. The observed substrate concentrations may reflect a minimum of residual concentration, below which the microbial community has difficulty in taking up the substrate.

ISSN:0008-4166    

DOI:10.1139/m73-069

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A method of selecting temperature-sensitive mutants ofEscherichia coliwhich makes use of a double temperature shift combined with suicide as a result of incorporated3H-uridine is described. One mutant selected in this way shows restricted growth at 42 °C resulting from early inhibition of protein and ribonucleic acid (RNA) synthesis. In vitro assays of aminoacyl-transfer RNA synthetase activity indicated a complete absence of active glycyl-transfer RNA synthetase in the mutant. This enzyme activity in the mutant was distinguishable from the wild type by its rapid inactivation at 28 °C in cell-free extracts. Infection of the temperature-sensitive mutant with bacteriophage T4 did not alter the heat-sensitivity of the mutant enzyme. The mutation is 72% cotransducible with thexyllocus.

ISSN:0008-4166    

DOI:10.1139/m73-070

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

NADP-specific glutamate dehydrogenase (GDH) fromSalmonella typhimuriumwas purified 190-fold by heat treatment, ammonium sulfate fractionation, DEAE-Sephadex chromatography, reverse ammonium sulfate fractionation, and gel filtration. The enzyme proved to be stable to 55 °C, and displayed a pH optimum at 8.6 in the amination reaction. The sedimentation coefficient of GDH, as determined by sucrose density gradient centrifugation, was about 10.3 S. From gel filtration chromatography, the molecular weight and Stokes' radius for the enzyme were estimated at 280 000 daltons and 54 × 10−8 cm, respectively. Unusual resistance was displayed by the enzyme to high concentrations of the protein denaturants, urea, SDS, and guanidine hydrochloride.

ISSN:0008-4166    

DOI:10.1139/m73-071

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A 190-fold purified preparation of NADP+-specific glutamate dehydrogenase ofSalmonella typhimuriumwas used for the determination of kinetic parameters of the substrates, NADPH, NH4+, and α-ketoglutarate, in the direction of glutamate synthesis, and NADP+and glutamate in the reverse direction. The kinetic constants determined from this study suggest a biosynthetic role for the enzyme. Based on an analysis of the data derived from initial velocity and product inhibition studies, the reaction mechanism was postulated to be ordered Ter Bi with NADPH as the first substrate to bind in the forward direction, and NADP+binding first in the reverse direction.Of the several metabolites tested for a possible function in the regulation of GDH activity, onlyL-malate andL-glutamine appeared to exert an appreciable influence on the enzyme. ATP and AMP at a concentration of 0.8 mM were found to enhance GDH activity by 68% and 6%, respectively, but at high concentrations, both the adenine nucleotides proved to be inhibitory.

ISSN:0008-4166    

DOI:10.1139/m73-072

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The isolated double-track layer of a gram-negative marine pseudomonad was subjected to a number of treatments designed to extract or to digest either phospholipid or protein. Extraction with chloroform–methanol caused aggregation and disruption of the double-track vesicles, a loss of the cleavage plane in frozen preparations, and a disappearance of the ring-like X-ray diffraction pattern which indicates side-by-side packing of the hydrocarbon tails of the phospholipids. Digestion with phospholipase-C, following ethylenediaminetetraacetate (EDTA) treatment, had the same effects except that the diglycerides freed by the action of the enzyme formed paracrystalline lamellar aggregates. This suggests that phospholipids are very important to the structural integrity of the double-track layer, that the layer of phospholipids is centrally located, and that this component of this membrane-like structure is responsible for the X-ray diffraction pattern produced by this material.Protein depletion by urea treatment or by pronase digestion causes increased aggregation of vesicles but these structures are not significantly disrupted, the cleavage plane is present in a stronger form in frozen material, and the X-ray diffraction pattern is unchanged. This suggests that proteins are superficially located and not as important as phospholipids in the structural integrity of this layer.The effects of protein depletion and of phospholipid depletion on the double-track layer are very similar to the effects of the same treatments on membranes, which supports the suggestion that the double-track layer has a membrane-like molecular architecture. The suggestion that this layer constitutes the barrier layer in the gram-negative cell wall is supported by our observations that sodium lauryl sulfate (SLS), EDTA, and polymyxin, which affect the penetrability of the cell wall of whole cells, have been shown to affect the molecular architecture of the isolated double-track layer used in these studies.

ISSN:0008-4166    

DOI:10.1139/m73-073

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A system consisting of isocitrate, NADP, and ferredoxin can supply reducing power for acetylene reduction in broken-cell preparations ofGloeocapsasp. LB 795. It is suggested that this system plays a physiological role in supporting nitrogen fixation, at least under conditions unfavorable for the photochemical generation of reductant.

ISSN:0008-4166    

DOI:10.1139/m73-074

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

SeveralCaulobacterphages inhibit or kill host bacteria without phage production. Host-range studies showed that many of theCaulobacterstrains that were sensitive to a particular phage were not productive hosts for that phage. Phage adsorbed to both productive and non-productive sensitive hosts but not to non-sensitive controls, nor to host cells treated with NaCN, or cells killed by ultraviolet (UV), heat, formaldehyde, or desiccation. Lysis from without could not be demonstrated. Ultraviolet-inactivated phage showed the same inhibitory effect on the non-productive hosts as did viable phage; however, purified tails of phage ø6 did not exhibit the capacity to inhibit the sensitive hosts. The UV adsorbance of the suspending medium of cell–phage mixtures increased with time in the case of the non-productive strain but not the productive strain. This increase indicates that leakage of intracellular material into the medium occurred as a result of phage infection of the non-productive strain but not the productive strain.

ISSN:0008-4166    

DOI:10.1139/m73-075

出版商:NRC Research Press    

年代:1973

数据来源: NRC