1H NMR-BASED METABOLIC PROFILE OF LACTOBACILLUS SALIVARIUS FDB89 UNDER OSMOTIC STRESS

In their natural habitats and application environments, lactic acid bacteria are often exposed to osmotic changes. At metabolic level, bacteria are able to de novo synthesize or uptake specific solutes from environment to maintain constant turgor pressure. In the work, the H-1 nuclear magnetic resonance (NMR) spectroscopy based on intracellular metabolites profiles of Lactobacillus salivarius under hyper-osmotic growth conditions was characterized. New characteristic peaks of compatible compounds, such as betaine, carnitine, choline and/or their derivatives were detected. Especially, the cytoplasmic concentrations of proline increased dramatically when the osmolarity was raised from about 0.40 to 1.84 osmol/kg by adding 0.8 mol/l NaCl to the medium. Comparative analysis of the metabolites of L. salivarius FDB89 grown under aerobic and anaerobic conditions with NaCl stress revealed an overlap of up-regulated compounds of more than 50%. 2-aminobutyrate, pyruvate, glycine, trimethylamine-N-oxide, and acetylcholine were detected only under anaerobic condition, and 2-oxoglutarate, tyrosine, glutamine and glutamate were detected only under aerobic condition, which suggested oxygen also has a nonnegligible effect on osmotic response in L. salivarius FDB89.