La alta relación C/N induce una respuesta fermentativa en Bradyrhizobium japonicum

LÓPEZ GARCÍA, S.L.; LÓPES, M.F.; PÉREZ JIMENEZ, J.; QUELAS, I.; DRAGHI, W.O.; ALTHABEGOITI, M.J.; MONGIARDINI, E.; LODEIRO, A.R.

Crodoba, Argentina

Congreso; XXIII Reunión Latinoamericana de Rhizobiología; 2007

Asociación Latinoamericana de Rhizobiología

Bradyrhizobium japonicum infectivity and competitiveness for soybean nodulation are stimulated under N-starvation. In free-living rhizobia, N assimilation proceeds through the high-affinity glutamine-synthetase (GS) - glutamate-synthase (GOGAT) cycle. We observed that under N-starvation, B. japonicum shows an increase in GS activity. Furthermore, we observed a high concentration of extracellular polysaccharide (EPS) and carbon storage polymers like polyhydroxybutyrate in this condition. Indeed, EPS composition was not altered in relation with N availability. To get a deeper insight into the relationship between N assimilation and C accumulation pathways, we analyzed by GC/MS and HPLC the concentration of diverse metabolites in rhizobia grown with high or low C/N ratio. With high C/N ratio there was an increase of lactate, citrate, isocitrate and others TCA-cycle intermediate concentrations, as well as a decrease in concentration of EPS synthesis precursors. Taken together, these results show a fermentative response of B. japonicum against N-starvation.