[Synthesis and breakdown of poly-beta-hydroxybutyric acid in Rhizobium lupini]

The effect of various substrates on synthesis and decomposition of poly-beta-hydroxybutyric acid (PHBA) was studied in cell suspensions of the effective strain of Rhizobium lupini and in suspensions of the bacteroids of this strain which were isolated from lupine nodules at different growth stages of the plants. Glucose and beta-hydroxybutyrate were found to be the best substrates for synthesis of PHBA in all variants. The content of PHBA in the presence of these substrates increased in suspensions by 2.0 to 2.5 times during ten hours of incubation. In the presence of succinate, PHBA was actively synthesized only by the bacteroids isolated during the stage of active nitrogen fixation (flowering of the plants). In the absence of exogenous substrates, PHBA was decomposed, especially if ammonium ions were present in suspensions. No synthesis of PHBA was registered in the presence of ammonium and glucose, and the rate of PHBA decomposition was high in this case during the stage of active nitrogen fixation.