A METABOLOMIC APPROACH TO CHARACTERIZE ACID-ADAPTED BATCH CULTURES OF Sinorhizobium meliloti

DRAGHI, W.O.; DEL PAPA, M.F.; MARTINI, C.; BARSCH A.; PUHLER, A.; NIEHAUS, N.; LAGARES, A.

Córdoba

Congreso; XI Congreso Argentino de Microbiología General; 2015

Sinorhizobium meliloti is a soil bacterium with the ability to establish a nitrogen-fixing symbiosis with different species ofMedicago, Melilotus and Trigonella. In natural soil environment both partners need to surpass diverse biotic and abiotic stressesto achieve a successful symbiosis. In particular, the Medicago-S. meliloti / medicae symbiosis has been largely recognized ashighly sensitive to (even moderate) acid stress. Thus, to cope with extracellular acidity S. meliloti is able to induce an adaptiveacid tolerance response (ATR+), which not only promotes better survival rates but also improves symbiotic competitiveness. Tocharacterize the biochemistry of such adapted (ATR+) rhizobia, a metabolomic approach was used. Results showed changes inseveral compounds of the central C-metabolism (mainly those involved in the pentose phosphate pathway) with an decrease inthe intracellular NAD(P)H/NAD(P)+ ratio. The lower availability of reducing power is in agreement with a decreasedconcentration of polyhydroxybutirate. Results of the observed metabolic remodelling suggest that the balance of reducing powercould be a relevant factor for maintaining the cellular homeostasis under acid stress. Further analysis will be necessary toprogress in understanding how the metabolic changes here reported mediate the higher acid tolerance of the rhizobia and theirmore competitive phenotype on the host roots nodulation under acidic conditions.