Nitrogen-fixing symbiosis

Treatment of an extracellular polysaccharide of Rhizobium japonicum (an important factor for nitrogen-fixing symbiosis between bacteria and soybeans) with liquid HF (—40°, 30 min) gave mono- and oligo-saccharides involving 0- -D-glucopyranosyl-( 1 - 3)-C>-(4-0-acetyl-a-D-galactopyrano-syluronic acid)-(l— 3)-D-mannose and its 1-fluoride. 

C2oH320t8 560.462 Constit. of the repeating unit of an extracellular polysaccharide of Rhizobium japonicum strain 3Ilb 138. May play a role in recognition place between the bacteria legumes in the establishment of nitrogen fixing symbiosis Syrup. 

In symbiotic systems, like these where the association appears quite intimate or the symbiont population occupies a majority of the host cell volume, the relationship is assumed necessary (Douglas, 1998) and/or beneficial. The benefit of the DDA relationship is not fuUy understood nor characterized, and because N2 fixation has been measured when the DDAs are present, it is presumed that some of the nitrogen fixed by the symbiont is transferred to the host diatom. To date, there are only a few studies that have attempted to understand the nature of the symbiosis between the Richelia symbiont and the host diatom. 

Villareal, T. A. (1989). Division cycles in the nitrogen-fixing Rhizosolenia (BaciUariophyceae) Richelia (Nostocaceae) symbiosis. Br. Phycol.J. 24, 357—365. 

A defined role for flavraies as signaling molecules has been realized in the symbiosis between legumes and nitrogen-fixing rhizobia. Among other flavonoids, flavones from the host roots are exuded and selectively recognized by the respective... 

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