Role of Symbiotic Auxotrophy in the Rhizobium-Legume Symbioses

Symbiotic auxotrophy occurs in both determinate pea and indeterminate bean nodules demonstrating its importance for bacteroid formation and nodule function in legumes with different developmental programmes. However, only small quantities of branched chain amino acids are needed and symbiotic auxotrophy did not occur in the Sinorhizobium meliloti-alfalfa symbiosis under the conditions measured. The contrasting symbiotic phenotypes of aap bra mutants inoculated on different legumes probably reflects altered timing of amino acid availability, development of symbiotic auxotrophy and nodule developmental programmes

A physiological analysis of the role of the truB gene in Escherichia coli

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Symbiotic properties of 4 week old bean plants.

<p>The values are the mean ± SEM of plants inoculated with RU2222 (n = 8) and RU1933 (n = 6). P-values were determined by ttest.</p

Plant dry weights and acetylene reduction (AR) of alfalfa (<i>M. sativa</i>) at 4 weeks.

<p>The values are the mean ± SEM of plants inoculated with 2011 (n = 18), LMB211 (n = 18) and uninoculated control plants (n = 6). ND  =  not determined.</p

Transport of amino acids by strains of <i>R. leguminosarum</i> bv. <i>viciae.</i>

<p>Vmax and Km were calculated from transport rate mean values of 3 independent cultures measured at 5 concentrations from 0.1 µM up to 5 µM. Vmax values are given in nmol min⁻¹mg⁻¹ protein ± SEM and Km mean values are given in nM ± SEM. ND  =  not determined.</p

Transport of amino acids and plant dry weights by strains of <i>R. leguminosarum</i> bv <i>phaseoli.</i>

<p>All strains were grown on AMS glucose/NH₄Cl minimal medium. Rates of uptake are expressed as nmol min⁻¹mg⁻¹ protein. Values are the mean ± SEM of determinations from three or more independent cultures. Dry weights (g plant⁻¹) are averages of >27 plants.</p

TEM pictures of bacteroids of wild-type (A and B) and RU1933 <i>aap bra</i> (C and D).

<p>A and C are pictures taken of 4 week old nodules, B and D of 6 week old nodules. Size bars are 500 µm.</p

Transport of amino acids by strains of <i>Sinorhizobium meliloti.</i>

<p>All strains were grown in M9 modified glucose/NH₄Cl minimal medium. Rates of uptake are expressed as nmol min⁻¹mg⁻¹ protein. Values are the mean ± SEM of determinations from three independent cultures, except for strain 2011 alanine, leucine and valine transports, which just served as controls and represent single measurements. ND  =  not determined.</p