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  • 1
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 38 (1988), S. 35-49 
    ISSN: 0730-2312
    Keywords: alfalfa ; dicarboxylic acid ; energy source ; chlorpromazine ; bacteroid ; nitrogenase ; respiration ; rhizobium meliloti ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Bacteroids having a high level of respiration-supported nitrogenase activity were isolated from nitrogen-fixing alfalfa root nodules. Gentle maceration under anaerobic conditions in the presence of sodium succinate and a fatty acid scavenging agent were employed in this method.A large proportion of isolated bacteroids retained a triple membrane structure as shown by transmission electron microscopy. Dicarboxylic acids of the TCA cycle (malate, fumarate, succinate), but not glutamate or aspartate, supported sufficient respiratory activity to supply the nitrogenase system with ATP and reducing equivalents and to protect the nitrogenase system from inactivation by 4% oxygen over a period of 20-30 min. Sugars did not support nitrogenase activity in intact bacteroids. The properties of the isolated bacteroids were ascribed to minimal damage to the cytoplasmic membrane and peribacteroidal membrane during isolation.With succinate as substrate and oxygen as terminal electron acceptor, initial nitrogenase activity was determined at 4% oxygen in the gas phase of the assay system employed. At this oxygen concentration, the sustained rate of acetylene reduction by respiring bacteroids was linear up to 30 min. Bacteroid activity declined rapidly with time of exposure to oxygen above 4% in the gas phase. The optimum temperature range for this activity was 10-20°C. Nitrogenase activity was measurable at incubation tempertures below 10°C under 4% oxygen. Functionally intact bacteroids had little nitrogenase activity under anaerobic conditions in the presence of an external source of ATP and reductant. Treatment of the bacteroids with chlorpromazine eliminated respirtation-supported activity and rendered the bacteroid cell membrane permeable to external ATP. Bacteroids treated with chlorpromazine had high acetylene reducing activity with external ATP and dithionite in the absence of oxygen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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