Nitrogen fixation and poly-β-hydroxybutyric acid content in bacteroids ofRhizobium lupini andRhizobium leguminosarum

Summary

Experiments carried out in a sand culture have demonstrated that during the growth ofVicia faba andLupinus luteus inoculated with effective strains of Rhizobium, and when the behaviour of bacteroids isolated from nodules ofLupinus luteus, Pisum sativum andVicia faba which had been inoculated with effective and ineffective strains and when comparisons were made between bacteriods isolated from effective nodules ofVicia faba andLupinus luteus either at midday or at midnight there is a reverse correlation between the intensity of nitrogen fixation and respiration, on the one hand, and the content of poly-β-hydroxybutyric acid (PHB), on the other. This evidence suggests an important role played by PHB in the supply of symbiotic fixation with energy and carbon substrates.

Glucose and β-hydroxybutyrate were the best substrates for PHB synthesis in the suspension of bacteroids of an effective strain ofR. lupini at all stages of plant growth. At the stage of active nitrogen fixation (flowering) PHB was actively synthesized in the presence of succinate. In the absence of exogenous substrates the polymer degraded, the process being enhanced in the presence of ammonium ions. When ammonium was added together with glucose, PHB synthesis did not occur and at the flowering stage the polymer broke down particularly rapidly. re]19760505