A metabolomics approach to characteriza acid-adapted batch cultures of Sinorhizobium meliloti.

DRAGHI WO; DEL PAPA M. F.; MARTINI M. C; BARSCH A; PÜHLER, A.; NIEHAUS K:; LAGARES A.

Congreso; XI SAMIGE; 2015

SAMIGE

Sinorhizobium meliloti is a soil bacterium with the ability to establish a nitrogen-fixing symbiosis with different species of Medicago, Melilotus and Trigonella. In natural soil environment both partners need to surpass diverse biotic and abiotic stresses to achieve a successful symbiosis. In particular, the Medicago-S. meliloti / medicae symbiosis has been largely recognized as highly 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. To characterize the biochemistry of such adapted (ATR+) rhizobia, a metabolomic approach was used. Results showed changes in several compounds of the central C-metabolism (mainly those involved in the pentose phosphate pathway) with an decrease in the intracellular NAD(P)H/NAD(P)+ ratio. The lower availability of reducing power is in agreement with a decreased concentration of polyhydroxybutirate. Results of the observed metabolic remodelling suggest that the balance of reducing power could be a relevant factor for maintaining the cellular homeostasis under acid stress. Further analysis will be necessary to progress in understanding how the metabolic changes here reported mediate the higher acid tolerance of the rhizobia and their more competitive phenotype on the host roots nodulation under acidic conditions.