- Volume 119, Issue 2, 1980
Volume 119, Issue 2, 1980
- Physiology And Growth
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The Relationship Between Hydrogenase and Nitrogenase in Azotobacter chroococcum: Effect of Nitrogen Sources on Hydrogenase Activity
More LessThe effects of different nitrogen sources on the H2-uptake hydrogenase activity were studied in batch-grown and carbon- or sulphate-limited chemostat cultures of Azotobacter chroococcum. Hydrogenase activity was significantly higher in N2-fixing than in NH4 +- or NO3 −-dependent cultures under carbon limitation or in early-stationary phase batch growth but was not influenced by the nitrogen source in sulphate-limited cultures. Hydrogenase activity developed nearly two generation times later than nitrogenase activity during the transition from NH4 +- to N2-dependent growth in carbon-limited cultures. A possible explanation is that H2 produced by nitrogenase induced hydrogenase synthesis. Carbon-limited N2-fixing cultures possessed higher hydrogenase activity than did sulphate- or O2-limited cultures. It appears that carbon substrates or metabolites act as primary repressors of hydrogenase activity and that secondary effectors, such as nitrogen sources or H2, act when such repression is removed.
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The Influence of Carbon Dioxide and Oxygen Partial Pressures on Chlorella Growth in Photosynthetic Steady-state Cultures
More LessThe effects of O2 and CO2 partial pressures in the range 0 to 1 atm on the maximum growth rate, starch production and photosynthetic efficiencies of growing cultures of Chlorella were determined. Stepwise increases of about 0.2 atm in the partial pressure of either gas inhibited growth, often completely. In contrast, gradual increases (steps of less than 0.1 atm) in the partial pressure of either gas maintained growth, and the cultures became adapted to high partial pressures. Adapted cultures tolerated 0.6 atm CO2 or 0.8 atm O2 without any growth inhibition as measured by maximum specific growth rate. Also, starch production was little affected by the increases in O2 or CO2 partial pressures.
The photosynthetic efficiency, as measured by the growth yield from light (400 to 700 nm wavelength) absorbed, and the maintenance energy were the same in adapted cultures with the O2 partial pressure at either 0.2 or 0.8 atm. The maximum growth yield from light was 0.0172 g kJ−1, with 95 % confidence limits of 0.0156 to 0.0189. The maintenance energy was 1.27 kJ (g dry wt)−1 h−1, with 95 % confidence limits of 0.89 to 1.65. The photosynthetic efficiency in light-limited cultures was 36.5 %, with 95 % confidence limits of 33 to 40 %.
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- Short Communication
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Isolation of Extremely Halophilic Bacteria Able to Grow in Defined Inorganic Media with Single Carbon Sources
More LessPigmented pleomorphic rods morphologically similar to Halobacterium volcanii were isolated from a salt pond near Alicante, Spain. The salt concentration range for growth (10 to 35 %, w/v, total salts) was more moderate than that typical of Halobacterium. Twenty-two strains were characterized as members of the genus Halobacterium, but were distinguished from currently recognized species by the absence of complex nutrient requirements, a rapid growth rate, nutritional versatility and salt-dependent pigment production. A typical strain (R-4) has been deposited in the Czechoslovak Collection of Microorganisms, no. CCM 3361.
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Asparaginase II of Saccharomyces cerevisiae: Characterization of a Mutation that Affects Expression in Rapidly Growing Cells
More LessA regulatory mutation has been identified that reduces expression of asparaginase II in exponential phase cells of Saccharomyces cerevisiae to 25 % or less of the wild-type activity. Mutants in this gene (ASP4) can be derepressed for asparaginase II by nitrogen starvation and will grow with D-asparagine as the sole nitrogen source. ASP4 assorts independently from ASP2 and ASP3. Mutation in either of the latter two genes results in lack of asparaginase II activity under any growth conditions.
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Perturbation of Enzyme Activity in Cells of the Fission Yeast Schizosaccharomyces pombe Subjected to Continuous-flow Centrifugation
More LessFluctuations in glutamine synthetase activity were observed when exponentially dividing cells of Schizosaccharomyces pombe were synchronized by continuous-flow centrifugation. These fluctuations were not seen in a control culture in which cells were allowed to grow asynchronously following filtration. However, when an asynchronous control culture was prepared by allowing cells to pass quickly through the continuous-action rotor without size selection, marked fluctuations in glutamine synthetase activity occurred. It is concluded that when the continuous-flow size selection method of cell synchronization is used, suitable control experiments are essential before any conclusions can be drawn about how enzyme synthesis is regulated during the cell cycle.
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Hydrogen-dependent Growth and Autotrophic Carbon Dioxide Fixation in Derxia
More LessFour strains of Derxia grew autotrophically with H2, as the energy source in the absence of an organic carbon substrate. Growth experiments with 14CO2, showed that 45% of the dry weight was carbon incorporated from CO2. Autotrophically grown cells showed significant H2-dependent CO2, fixation and high activities of H2,-uptake hydrogenase and ribulose-1,5-bisphosphate carboxylase compared with cells grown heterotrophically. Of several other aerobic N2,-fixing bacteria tested (excluding Rhizobium japonicum), only Xanthobacter autotrophicus was able to grow autotrophically.
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- Taxonomy
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A Taxonomic Study of Gardnerella vaginalis (Haemophilus vaginalis) Gardner and Dukes 1955
More LessFifty-five strains received as Haemophilus vaginalis or as catalase-negative coryneform bacteria from the vagina together with 61 marker cultures were subjected to numerical phenetic analyses using 149 unit characters. The data were examined using the simple matching (S SM), Jaccard (S J) and pattern (D P) coefficients and clustering was achieved using the average linkage algorithm. Cluster composition was not markedly affected by the coefficient used or by test error, estimated at 6.5 %. The H. vaginalis strains formed a tight cluster which was only distantly related to representatives of the genera Arthrobacter, Cellulomonas, Corynebacterium sensu stricto, Erysipelothrix, Haemophilus, Kurthia, Lactobacillus, Listeria and Propionibacterium but shared a high overall affinity to unclassified catalase-negative coryneforms which formed a discrete taxon, cluster 9. The H. vaginalis strains could be distinguished from the related strains in cluster 9 by several unrelated phenotypic characters.
Using the S1 endonuclease assay, DNA-DNA hybridizations were performed with representative strains from the numerical study as well as with reference strains of Bifidobacterium and Actinomyces. Haemophilus vaginalis was found to be a genotypically legitimate group and its DNA showed little homology with DNA from the marker strains tested. The DNA base composition of H. vaginalis was 42 to 44 mol % guanine plus cytosine. A new genus should be created to incorporate strains known as H. vaginalis or Corynebacterium vaginale. The name Gardnerella vaginalis proposed by Greenwood & Pickett (1979) is supported.
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Serological Relatedness of Spiroplasmas Estimated by Enzyme-linked Immunosorbent Assay and Crossed Immunoelectrophoresis
More LessEnzyme-linked immunosorbent assay (ELISA) has been used to estimate the serological relatedness of spiroplasmas. The method was shown to be a sensitive and discriminating quantitative technique, with a minimum detection level of between 104and 105spiroplasmas. Antisera to Spiroplasma citri and corn stunt spiroplasma, and a monospecific antiserum to a purified membrane protein, spiralin, were used to compare spiroplasmas isolated from plant and insect hosts. Spiroplasma cell surface antigens were compared using intact cells as the antigens for ELISA, while the complete ranges of cell antigens were compared using lysed cells. Distinct serological groupings of spiroplasmas emerged, in accord with current schemes. Homology of some Spiroplasma citri and honeybee (BC3) spiroplasma antigens was confirmed by crossed immunoelectrophoresis. ELISA is discussed in relation to results from other serological typing procedures, and conditions for comparing isolates by tandem crossed immunoelectrophoresis are described.
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Rhodopseudomonas blastica sp.nov.: a Member of the Rhodospirillaceae
More LessInoculation of samples from a small eutrophic pond into pyruvate/malate medium at neutral pH yielded a new species of the Rhodospirillaceae described here as Rhodopseudomonas blastica. The cells are ovoid to rod-shaped, 1 to 2.5 μm long and 0.6 to 0.8 μm wide, non-motile and multiply by a process of sessile budding. The photosynthetic membrane system consists of lamellae parallel to and underlying the cell membrane. The photopigments consist of bacteriochlorophyll a and carotenoids of the spheroidene group. Cells can grow anaerobically in the light using a wide range of organic compounds. Aerobic growth in the dark is also possible. Nicotinic acid and thiamin are required as growth factors. Good photolithotrophic growth with H2 is possible, but sulphide and thiosulphate cannot be used as electron donors. As this species has properties lying between the two groups of existing Rhodopseudomonas species, i.e. those which show intercalary growth and those which multiply by budding (asymmetric polar growth), a new species is hereby proposed.
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