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  • Bacillus acidocaldarius  (2)
  • Cucurbita texana  (2)
  • Springer  (4)
  • Amsterdam : Elsevier
  • 1
    ISSN: 1432-072X
    Keywords: Molar growth yields ; Thermoacidophile ; Respiratory chain energy conservation ; Membrane permeability ; Temperature and pH ; Bacillus acidocaldarius
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The molar yield coefficients (Y glucose, Y O 2) of glucose-limited continuous cultures of the thermoacidophile Bacillus acidocaldarius have been measured as a function of dilution rate as well as over a range of temperature and pH (51°C to 64°C, pH 2.8–5.5) at a fixed dilution rate of approximately 0.1 h-1. The highest growth yields were observed at 51°C and pH〉4.3 (Y glucose 54.8 g cells · mol glucose-1, Y O 2 15.0 g cells · mol O 2 -1 ), but were very much lower than those of mesophilic neutrophiles of similar respiratory chain composition to B. acidocaldarius. Even lower growth yields were observed when the temperature was raised or when the pH was lowered, lowest yields occurring at 64°C and pH 2.8 (Y glucose 23.4 g cells · mol glucose-1, Y O 2 5.9 g cells · mol O 2 -1 ). These decreases in growth yield could be correlated with increases in the permeability of the cytoplasmic membrane to protons, i.e. cells needed to catalyse enhanced rates of substrate oxidation in order to avoid a potentially lethal acidification of the cytoplasm. This strategy appears to be successful in that the specific death rates in situ were very low for all cultures except those growing under the most extreme conditions (64°C, pH 2.8).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Bacillus acidocaldarius ; Response surface analysis ; Temperature and pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A minimal-salts medium has been optimised to support the growth of the acidophilic thermophilic bacterium Bacillus acidocaldarius. This medium was used during a study of the effect of temperature and pH on the growth rate and growth yield of this organism in batch cultures; a statistical method was used to design the experimental points, and the data were subjected to a response surface analysis which allowed the growth rate and growth yield to be predicted over the entire temperature and pH range from a minimum number of experimental points. The results indicate different responses for growth rate (optimum, 60°C, pH 4.1) and growth yield (optimum tending towards low temperature and neutral pH).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 92 (1996), S. 885-890 
    ISSN: 1432-2242
    Keywords: Key words  Microgametophyte selection ; Pollen selection ; Pollen competition ; Cucurbita texana ; Cucurbita pepo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   We examined the effects of pollen selection for rapid pollen-tube growth on progeny vigor. First, we crossed a wild gourd (Cucurbita texana) to a cultivated zucchini (Cucurbita pepo cv `Black Beauty') to produce an F1 and then an F2 generation. Half of the F1 seeds were produced by depositing small loads of C. texana pollen onto the stigmas of C. pepo. These small pollen loads were insufficient to produce a full complement of seeds and, consequently, both the fast- and the slow-growing pollen tubes were permitted to achieve fertilization. An F2 generation was then produced by depositing small loads of F1 pollen onto stigmas of F1 plants. The F2 seeds resulting from two generations of small pollen loads are termed 'the non-selected line' because there was little or no selection for pollen-tube growth rate on these plants. The other half of the F1 and F2 seeds were produced by depositing large pollen loads (〉10000 pollen grains) onto stigmas and then allowing only the first 1% or so of the pollen tubes that entered the ovary to fertilize the ovules. We did this by excising the styles at the ovary at 12–15 h after pollination. The resulting F2 seeds are termed `the selected line' because they were produced by two generations of selection for only the fastest growing pollen tubes. Small pollen loads from the F2 plants, both the selected and the non-selected lines, were then deposited onto stigmas of different C. pepo flowers, and the vigor of the resulting seeds was compared under greenhouse and field conditions. The results showed that the seeds fertilized by pollen from the selected line had greater vegetative vigor as seedlings and greater flower and fruit production as mature plants than the seeds fertilized by pollen from the non-selected line. This study demonstrates that selection for fast pollen-tube growth (selection on the microgametophyte) leads to a correlated increase in sporophyte (progeny) vigor.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 92 (1996), S. 885-890 
    ISSN: 1432-2242
    Keywords: Microgametophyte selection ; Pollen selection ; Pollen competition ; Cucurbita texana ; Cucurbita pepo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the effects of pollen selection for rapid pollen-tube growth on progeny vigor. First, we crossed a wild gourd (Cucurbita texana) to a cultivated zucchini (Cucurbita pepo cv ‘Black Beauty’) to produce an F1 and then an F2 generation. Half of the F1 seeds were produced by depositing small loads of C. texana pollen onto the stigmas of C. pepo. These small pollen loads were insufficient to produce a full complement of seeds and, consequently, both the fast- and the slow-growing pollen tubes were permitted to achieve fertilization. An F2 generation was then produced by depositing small loads of F1 pollen onto stigmas of F1 plants. The F2 seeds resulting from two generations of small pollen loads are termed the non-selected line because there was little or no selection for pollen-tube growth rate on these plants. The other half of the F1 and F2 seeds were produced by depositing large pollen loads (〉10 000 pollen grains) onto stigmas and then allowing only the first 1% or so of the pollen tubes that entered the ovary to fertilize the ovules. We did this by excising the styles at the ovary at 12–15 h after pollination. The resulting F2 seeds are termed ‘the selected line’ because they were produced by two generations of selection for only the fastest growing pollen tubes. Small pollen loads from the F2plants, both the selected and the non-selected lines, were then deposited onto stigmas of different C. pepo flowers, and the vigor of the resulting seeds was compared under greenhouse and field conditions. The results showed that the seeds fertilized by pollen from the selected line had greater vegetative vigor as seedlings and greater flower and fruit production as mature plants than the seeds fertilized by pollen from the non-selected line. This study demonstrates that selection for fast pollen-tube growth (selection on the microgametophyte) leads to a correlated increase in sporophyte (progeny) vigor.
    Type of Medium: Electronic Resource
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