Beyond Chloride Brines: Variable Metabolomic Responses in the Anaerobic Organism Yersinia intermedia MASE-LG-1 to NaCl and MgSO4 at Identical Water Activity

Petra Schwendner, Maria Bohmeier, Petra Rettberg, Kristina Beblo-Vranesevic, Frédéric Gaboyer, Christine Moissl-Eichinger, Alexandra K. Perras, Pauline Vannier, Viggó T. Marteinsson, Laura Garcia-Descalzo, Felipe Gómez, Moustafa Malki, Ricardo Amils, Frances Westall, Andreas Riedo, Euan P. Monaghan, Pascale Ehrenfreund, Patricia Cabezas, Nicolas Walter, Charles Cockell

Growth in sodium chloride (NaCl) is known to induce stress in non-halophilic microorganisms leading to effects on the microbial metabolism and cell structure. Microorganisms have evolved a number of adaptations, both structural and metabolic, to counteract osmotic stress. These strategies are well-understood for organisms in NaCl-rich brines such as the accumulation of certain organic solutes (known as either compatible solutes or osmolytes). Less well studied are responses to ionic environments such as sulfate-rich brines which are prevalent on Earth but can also be found on Mars. In this paper, we investigated the global metabolic response of the anaerobic bacteriumYersinia intermediaMASE-LG-1 to osmotic salt stress induced by either magnesium sulfate (MgSO4) or NaCl at the same water activity (0.975). Using a non-targeted mass spectrometry approach, the intensity of hundreds of metabolites was measured. The compatible solutes L-asparagine and sucrose were found to be increased in both MgSO4and NaCl compared to the control sample, suggesting a similar osmotic response to different ionic environments. We were able to demonstrate thatYersinia intermediaMASE-LG-1 accumulated a range of other compatible solutes. However, we also found the global metabolic responses, especially with regard to amino acid metabolism and carbohydrate metabolism, to be salt-specific, thus, suggesting ion-specific regulation of specific metabolic pathways.