Metabolic analysis of acid-adapted (ATR+) Sinorhizobium meliloti

DEL PAPA, M.F.; PUHLER, A.; DRAGHI, W.O.; BARSCH A.; LAGARES, A.; ALBICORO, F.; NIEHAUS, K.

Pucón

Taller; III Taller Latinoamericano de PGPR; 2016

Universidad de La Frontera

Sinorhizobium meliloti establishes a nitrogen-fixing symbiosis with Medicago species. In the soilenvironment both partners need to surpass biotic and abiotic stress factors to achieve a successfulsymbiotic system. It is widely recognizable that the Medicago-Sinorhizobium symbiosis is highly sensitive to acid stress. To cope with low pH, S. meliloti is able to induce an acid tolerance response (ATR+response), which not only support a better survival under acidity, but also results in a more competitive symbiotic. To characterize the biochemistry of ATR+ rhizobia, a metabolomic approach was used. The results showed changes in the central carbon metabolic pathways making them more active for NAD(P)H supply, likely as a consequence of higher demands for this nucleotide under acid stress. Significant changes in 27 out of 61 detected metabolites were observed, including Gluconate-6-P, Glycerate-3-P, Gluconate, Pep, Serine, Homoserine, Fructose, Glycerate, O-succinyl-Homoserine, Fructose-6-P, Glycerate-2-P, 2-lsopropylmalate, Urea, Pyruvate, Homocysteine, Glucose-6-P, Lactic Acid, Alanine,Sucrose, Gluconolactone, Shikimate, a-Glycerophosphate, Methylcitrate, Proline, Uracil, myo-Inositol and Ribose-5-P. In addition enzymatic activities involved in synthesis/degradation of some of the altered metabolites showed congruent responses with the observed changes their substrates/products cytoplasmic concentration. The observed metabolic changes are part of the induced cellular activities to help maintaining the intracellular pH homeostasis in the cytoplasm. New proteomic and transcriptomic data of the ATR+ vs. ATR- rhizobia will be necessary to help understanding how the more acid-tolerant rhizobia also express a more competitive symbiotic phenotype.