- Volume 134, Issue 4, 1988
Volume 134, Issue 4, 1988
- Physiology And Growth
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Growth Efficiency of Xanthomonas campestris in Continuous Culture
More LessXanthomonas campestris NCIB 11854 was grown glucose-limited in continuous culture at 28 °C, pH 6·8, in a defined minimal salts medium. Whole cells contained cytochromes b, c, aa 3, o-type cytochromes and possibly a 1, and yielded →H+/O quotients of up to approximately 6 for the oxidation of endogenous substrates. These data, by analogy with results obtained previously with other species of bacteria, suggest the presence of up to three sites of respiratory chain energy conservation. However, molar growth yields on glucose [Y max glucose = 53·6 g dry wt bacteria (mol glucose)−1] and oxygen [Y max O 2 = 26·4 g dry wt bacteria (mol O2)−1] were extremely low and indicated an ATP/O quotient of approximately 1 which was only marginally increased when corrected for polymer production. A relatively rapid decay of the pH gradient generated by in vitro respiration was observed, probably indicating either an enhanced permeability of the cytoplasmic membrane to H+ or a rapid rate of ATP turnover, either of which could in part account for the observed low growth efficiency of the organisms.
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Low Concentrations of Trifluoperazine Arrest the Cell Division Cycle of Saccharomyces cerevisiae at Two Specific Stages
More LessLow concentrations of trifluoperazine (TFP) reversibly inhibited vegetative growth of Saccharomyces cerevisiae. The cell cycle was analysed by flow cytometry using haploid a cells synchronized by α-factor arrest and several temperature-sensitive cell division cycle mutants (cdc). Cells were pulse-labelled with fluorescein-labelled concanavalin A (ConA-FITC) to determine cell division or stained with propidium iodide to determine the stage of cell cycle arrest by TFP. Cell growth was estimated from the changes in the relative intensity of scattered light, and budding was determined microscopically. When TFP was added before Start on release from α-factor arrest, after release of cdc28-arrested cells, and at transition from stationary phase to vegetative growth, cell growth, budding and DNA synthesis were inhibited. When TFP was added after execution of spindle pole body duplication, cell growth, bud emergence and DNA synthesis were not inhibited but cell division was inhibited and the cells arrested with buds at G2 + M. Using cdc mutants, the second stage of arrest by TFP was determined to be just before medial-nuclear division.
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Isolation and Characterization of Mevinolin Resistant Mutants of Saccharomyces cerevisiae
More LessMutants of Saccharomyces cerevisiae resistant to mevinolin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme-A (HMGCoA) reductase (EC 1.1.1.34) were isolated and one mutant (MV71) was extensively characterized. While growth of resistant strains in the presence of mevinolin was greater than that of the wild-type strain, mevinolin at the concentration used still inhibited growth. Diploids produced by mutant/wild-type matings showed levels of mevinolin resistance which indicated incomplete dominance. Sterol synthesis in the presence of mevinolin was inhibited in strain MV71 but to a lesser degree than seen in the wild-type strain. All mevinolin resistant mutants also demonstrated a slight resistance to the antibiotic nystatin. The subcellular location of HMGCoA reductase activity in MV71 and the wild-type strain were determined and it was shown that yeast HMGCoA reductase is not regulated by a dephosphorylation mechanism as has been shown for mammalian reductases. In vivo and in vitro studies of strain MV71 and the wild-type indicated that mevinolin resistance did not result in changes in HMGCoA reductase activity as has been demonstrated in mammalian systems. Based on growth data, sterol analysis, and the lack of detection of HMGCoA reductase activity differences between strain MV71 and the wild-type, mevinolin resistance is concluded to result possibly from a mutation in HMG2, one of the two functional yeast HMGCoA reductase genes, which accounts for a minor (up to 17%) amount of total cellular reductase activity.
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- Systematics
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Chemotaxonomy of Wall Type IV Actinomycetes Which Lack Mycolic Acids
More LessThe fatty acid, polar lipid, wall amino acid and menaquinone composition of 26 representatives of the genera Actinopolyspora, Faenia, Pseudonocardia, Saccharomonospora and Saccharopolyspora were determined. The fatty acid methyl esters were analysed by capillary column GC and the resultant quantitative data examined using principal components analysis. The amycolate wall type IV organisms were recovered as two clearly separated groups along the first principal components axis. Group I contained Faenia rectivirgula, Saccharopolyspora erythraea, S. hirsuta and Pseudonocardia thermophila. Actinopolyspora halophila was loosely associated with these organisms. Group II contained Saccharomonospora caesia and S. viridis, Pseudonocardia (Amycolatopsis) azurea and ‘Pseudonocardia (Amycolatopsis) fastidiosa’ and was more heterogeneous than group I. The results of the isoprenoid quinone and polar lipid analyses supported this classification based on statistical analysis of fatty acid data.
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Reverse Transcriptase Sequencing of 16S Ribosomal RNA from Faenia rectivirgula, Pseudonocardia thermophila and Saccharopolyspora hirsuta, Three Wall Type IV Actinomycetes Which Lack Mycolic Acids
More LessThe phylogenetic relationships of three mycolateless wall type IV actinomycetes, Faenia rectivirgula, Pseudonocardia thermophila and Saccharopolyspora hirsuta, were examined using reverse transcriptase sequencing of 16S ribosomal RNA. The sequences generated were aligned and the level of sequence homology calculated. The homology values were then used to produce a phylogenetic tree and to estimate S AB values for the construction of a dendrogram. Both analyses show the three taxa to be closely related genera which form a distinct subdivision within the broader phylogenetic grouping defined by Mycobacterium, Dactylosporangium and their relatives.
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