Metabolome analysis of acid grown Sinorhizobium meliloti (Sme)

DRAGHI, W.O., LOZANO, M., GIUSTI, M.A., PISTORIO, M. Y LAGARES, A.

Rosario, Sante fe, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Sme is an alfa-proteobacteria able to fix nitrogen-in symbiosis with Medicago spp. As soil microorganisms, rhizobia must overcome different stress conditions in free-living before entering the plant root. Soil acidity is a challenging environmental stress frequently present in agricultural fields, and Sme is particularly sensitive to the acid media. We approached a metabolome analysis of acid-stressed rhizobia to get a deeper insight into the physiology of the acid growth. Bacterial cells were grown in batch cultures using defined minimal medium (early log phase of growth), both at neutral and moderately acid (pH 6.1) pH. It is already known that during acid cultivation Sme triggers an Acid Tolerance Response. Seventy metabolites from cells in ATR phase were analyzed by GC/MS and compared with the same compounds from the neutral cultures. Significant differences in several amino acid were observed (p=0.05). Analysis of the central carbon metabolism showed that under acid cultivation rhizobia accumulate metabolites that belong to the pentose phosphate pathway (PPP); together with an increase of metabolites that connect PPP with the TCA cycle. The increase in the biosynthetic PPP intermediates correlates with a concomitant increase in exopolysaccharide production, and most likely with a decrease in the aerobic metabolism as shown by lower amounts of the first two TCA intermediates