RESPIRATORY ENZYME SYSTEMS IN SYMBIOTIC NITROGEN FIXATION I

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Abstract
Methods for the preparation of a suspension of "resting cells" of Rhizobium trifolii suitable for the determination of its respiratory functions were developed. Such suspensions can be stored at 3[degree] C for several days without loss in activity. The optimum pH range for respiration of R. t. is 5.1 and 7 with limits at pH 4 and 9. The opt. temp. range is 36-38[degree]C, in comparison with 28-30[degree] C for growth. The value of the Arrhenius temp. characteristic is 10,850 [plus or minus] 365 cal. The rate of respiration is independent of the conc. of glucose throughout the range investigated ([image]/10-[image]/1000). At low concs. of glucose only about 60% of the glucose used appears as CO2; the remainder is probably assimilated or converted in gum. Comparison of the O2 uptake and rate of decoloration of methylene blue by R. t. in the presence of different types of H donators indicated that the 4-carbon dicarboxylic acids are superior to carbohydrates, polyhydric alcohols and fatty acids.