摘要:

The glucose-6-phosphate dehydrogenase fromNeisseria gonorrhoeaewas inhibited by long-chain fatty acid acyl-coenzyme A derivatives. The inhibition was increased at low concentrations of glucose 6-phosphate and was greater with the NAD-linked activity (ca. 0.05 mMinhibitor required for 50% inhibition) than with the NADP-linked activity (ca. 0.2 mMrequired for 50% inhibition). Bovine serum albumin and spermine could prevent the inhibition by the acyl-coenzyme A derivatives, but neither of these compounds nor high concentrations of cofactors or substrate could reverse the effect. Dilution of enzyme–inhibitor preincubation mixtures appeared to reverse the inhibition. The inhibition by stearoyl-coenzyme A was of the mixed type, and the inhibitor appeared to have a greater affinity for the free enzyme (Ki = 0.016–0.05 mM) than for enzyme bound to cofactor or substrate (Kis = 0.07–0.08 mM). Glucose-6-phosphate dehydrogenase activity was also inhibited competitively by adenosine 5′-triphosphate and was strongly regulated by adenylate energy charge values between 0.9 and 1.0. Kinetic and other characteristics of the enzyme are presented, and the possible role of glucose-6-phosphate dehydrogenase as a target for fatty acid toxicity in gonococci, mediated in the form of the acyl-coenzyme A derivatives, is discussed.

ISSN:0008-4166    

DOI:10.1139/m80-151

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Streptomyces antibioticuspossesses a tryptophan-inhibitable 3-deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP) synthetase whose synthesis is also repressed byL-tryptophan. Studies of the DAHP synthetase obtained by ammonium sulfate fractionation of a crude extract derived fromS.antibioticusrevealed that the enzymic activity was only partially inhibited by tryptophan. Inhibition of the DAHP synthetase activity was strongly pH dependent at values below 7.0. A number of tryptophan analogues was noted to inhibit the enzyme; by contrast, other aromatic amino acid end products failed to affect DAHP synthetase activity. Chorismic acid, a key intermediate in aromatic amino acid biosynthesis, was ineffective as an inhibitor when used alone; however, if supplied withL-tryptophan, a further reduction of DAHP synthetase activity (15–25%) was routinely observed.

ISSN:0008-4166    

DOI:10.1139/m80-152

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A microaerophilic nitrogen-fixing bacterium was isolated from surface-sterilized roots ofSpartina alternifloraLoisel growing in a Nova Scotian salt marsh. It is a small curved rod and is motile with a single polar flagellum. Metabolism is respiratory. Organic and amino acids, but not carbohydrates, serve as carbon and energy sources. The guanine + cytosine content of its deoxyribonucleic acid is 32.1 ± 1.0 mol%. Based upon morphological and biochemical characteristics this organism is assigned to the genusCampylobacterSebald and Veron 1963. It is distinguishable from other campylobacters by the presence of nitrogenase and urease, by the production of pigment from tryptophan, and by a combination of other biochemical traits. The association of this organism with plant roots further distinguishes it from other campylobacters which commonly inhabit animal, including human, tissues.

ISSN:0008-4166    

DOI:10.1139/m80-153

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The viability ofMethanospirillum hungatiiGP1 cells dropped rapidly when starved in a pH 7.0 phosphate buffer under 100% N2or 90% N2– 10% H2gas phase. The presence of H2during starvation tests resulted in a more rapid and an ultimately greater reduction of the number of initially viable cells than in the presence of N2only. The decrease in viability was observed concurrently with the decline of the ATP pool and the RNA content of the cells. The cell protein, carbohydrate, and amino acid pool also decreased. The cellular DNA content which increased initially under both gas phases subsequently decreased under N2–H2gas phase. However, there was no net decline in the DNA content of the cells. The results indicate thatM.hungatiiwould not survive prolonged periods of starvation.

ISSN:0008-4166    

DOI:10.1139/m80-154

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Fatty acid compositions of lipids from six bacteria and four yeasts were determined. Fatty acidde novosynthetases were investigated with respect to chain length specificity towards acyl-CoA primers of various chain lengths.Four species of bacteria (Bacillus subtilis,Corynebacterium cyclohexanicum,Micrococcus luteus, andPseudomonas maltophilia) possess branched-chain fatty acids of the iso and anteiso series as the major acids.De novosynthetases from these organisms exhibited specificity towards the chain length of the primer in the order butyrl-CoA > propionyl-CoA  acetyl-CoA. The remainder, two bacteria and all four yeasts, have the straight-chain type of fatty acids only and fall into two groups: (1)Eschericia coliB,Pseudomonas fluorescens, andSaccharomyces cerevisiae, which utilize the primers in the order acetyl-CoA > propionyl-CoA  butyryl-CoA; and (2)Candida sake,Candida tropicalis, andRhodolorula glutinis, which show the order propionyl-CoA > acetyl-CoA  butyryl-CoA.L-α-Keto-β-methylvalerate, a precursor of the branched-chain primers, can be used as a source of primer for fatty acid synthesis by the organisms with branched-chain acids but not by those with the straight-chain type.The results indicate that organisms having straight-chain fatty acids lack the branched-chain equivalents for two reasons: first, their enzymes are not active toward primers with more than three carbons, and second, they lack a system of supplying suitable branched-chain primers.It appears that activities ofde novosynthetases from the organisms having straight-chain fatty acids generally have much higher activities than those from the organisms possessing branched-chain fatty acids.

ISSN:0008-4166    

DOI:10.1139/m80-155

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The hemagglutinin of rubella virus has been purified by differential centrifugation through a sucrose density gradient after disruption of purified virus with Tween 80 – ether. The purified isolated hemagglutinin was then adsorbed on liposomes which had been prepared by mixing lecithin and dicetyl phosphate in a 3.5:1 molar ratio. The complex of hemagglutinin adsorbed on the virosomes had a higher sedimentation rate, enabling their separation from free hemagglutinin. It was thus possible to obtain a pure preparation of virosomes by rate zonal centrifugation in a sucrose density gradient containing 0.5 MNaCl. Immunoelectron microscopy showed aggregation of these virosomes with a rubella immune antiserum; this would suggest that the HA subunits are oriented in the same way as on the whole virus.

ISSN:0008-4166    

DOI:10.1139/m80-156

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

The interaction of cyclic adenosine 3′,5′-monophosphate (cAMP) with specific protein molecules was examined in the high-speed supernatant fraction of extracts made at stages throughout glycerol-induced myxospore development inMyxococcus xanthus. Experiments using 8-azido[32P]cAMP, a photoaffinity analogue of cAMP, and SDS – polyacrylamide gel electrophoresis showed that the nucleotide interacts with only a single protein band of 12 500 molecular weight. Both the identiy and amount of this protein remained constant throughout development. The binding protein was specific for cAMP; other nucleotides did not compete with cAMP for binding sites. A Scatchard analysis showed evidence of only a single class of binding sites with a high affinity for cAMP.

ISSN:0008-4166    

DOI:10.1139/m80-157

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Use of the fluorochrome 4′,6-diamidino-2-phenylindole∙2 HCl (DAPI) in ultraviolet microscopy revealed fluorescent objects in Brownian motion within the vacuoles of seven species of yeast. The abundance of these bodies increased when cells ofSaccharomyees cerevisiaewere transferred from growth medium to a glucose–phosphate solution, indicating that they contain polyphosphate. In addition, the effect on vacuolar fluorescence of supplementing a defined growth medium with amino acids provided evidence that they also containedS-adenosylmethionine. These deductions were supported byin vitrostudies of the interaction and fluorescence of polyphosphate,S-adenosylmethionine, and DAPI. Vacuolar fluorescence of cells in suspension in glucose–phosphate solution was less after addition of exogenous arginine, lysine, or glutamine but not after addition of alanine, aspartic acid, or methionine.Mithramycin was superior to DAPI as a fluorochrome for ultraviolet demonstration of yeast nuclei since it stained the nuclei much more intensely and did not fluoresce with other material in the cell

ISSN:0008-4166    

DOI:10.1139/m80-158

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

A study, using four types of water samples ranging from relatively pure stream water to water containing industrial and domestic effluents, was carried out to investigate the effect of storage temperature on four bacterial parameters: total coliform, fecal coliform, fecal streptococcus, and heterotrophic bacteria. In the study, each water sample was cooled immediately after collection to approximately 1.5 °C by storage in crushed ice. At 2-, 24-, 30-, and 48-h intervals, the sample was mixed, and a subsample was removed and tested. Three separate analyses for each parameter were made on each subsample. The data available for statistical analyses contained, in some cases, the values obtained for the three subsamples and, in others, the means of the three values. The data were analysed as replicated data and as part of the entire set. The analysed data indicated (i) that with the exception of heterotrophic populations, more than 75% of the samples were microbiologically stable for at least 24 h, (ii) that at least 50% of samples tested for heterotrophic densities were stable for a minimum period of 24 h, (iii) that the original water temperature and bacterial load do not appear to be consistent factors in the preservation of samples for microbiological analysis, and (iv) that nutrient levels, also, do not seem to be consistent factors in the preservation of water samples for microbiological analyses.

ISSN:0008-4166    

DOI:10.1139/m80-159

出版商:NRC Research Press    

年代:1980

数据来源: NRC

摘要:

Studies have been made on the toxicities of three inorganic (HgCl2, HgSO4, and NH2HgCl) and two organic (CH3HgCl and phenyl mercuric acetate (PMA)) mercury derivatives on planktonic algae (Nitzschia acicularisW. Sm. andTetraselmis suecicaButch.). Growth kinetics and fluorescence changes were used as criteria for assessing algal–metal responses.Methylmercury chloride was found to be the more toxic form, inhibiting growth of both species at levels of 0.025 ppm Hg. PMA inhibitedNitzschiaat the same concentration. Inorganic forms prevent growth of the diatom at 0.15–0.20 ppm Hg. Addition of inorganic mercury at concentrations of 0.05 ppm Hg resulted in reduction of the lag phase, increase in exponential growth rate, or both. Increasing mercury concentrations caused a gradual increase in the lag phase inT.suecicaand inN.acicularisonly with mercuric sulphate. Populations recovered from this initial effect and started to grow. The effect of inoculum size on mercurial toxicity was tested. The higher concentrations of mercury that still permit growth restricted the chlorophyll fluorescence to the central cellular area and the cells appear slimmed. This effect is highest in concentrations that inhibit growth.

ISSN:0008-4166    

DOI:10.1139/m80-160

出版商:NRC Research Press    

年代:1980

数据来源: NRC