Betaine and choline are important compatible solutes in Bacillus altitudinis under salt and glucose stress.

Abstract

Osmotolerant rhizobacteria, Bacillus altitudinis TR-19, has been subjected to osmotic stress by cultivating the cells in: (1) Luria Bertani (LB) broth medium, (2) LB broth supplemented with 1.8M NaCl, and (3) LB broth supplemented with 20% glucose incubated at 370C with shaking. Samples were drawn periodically for growth analysis and metabolome profile. The results demonstrated that cultivation of the osmotolerant rhizobacteria in 1.8M NaCl-supplemented LB medium and 20% glucose-supplemented LB medium prolonged the adaptation growth phase, suggesting that NaCl at 1.8 M and 20% glucose reduced cell growth rate, although the cells were still capable of growing at such high osmotic stress. Metabolites synthesised under different growth conditions, in rich media (LB broth) and under osmotic stress (1.8M NaCl-supplemented LB medium and 20% glucose-supplemented LB medium) also demonstrated striking differences in their profile. Under osmotic conditions in NaCl, much less metabolites were found than under non-stress condition, suggesting the changes in metabolites synthesis pathway. Under 20% glucose stress conditions, by using 20% glucose-supplemented LB medium, the number of metabolites were also found reduced but more metabolites were observed than under NaCl stress. Different metabolome profile under non-stress conditions, NaCl-stress, and glucose stress were also observed, suggesting the changes in the metabolic pathway. One of the metabolite synthesised under osmotic condition was betaine which is known as the derivative of amino acid glycine. Betaine was synthesised under NaCl and glucose stress. Under non-stress condition, choline was not detected, suggesting that betaine and choline are important compatible solutes under NaCl stress.