Occurrence of choline and glycine betaine uptake and metabolism in the family Rhizobiaceae and their roles in osmoprotection

The key physiological role of glycine betaine in the family Rhizobiaceae appears to be as an energy source, while its involvement in osmoprotection is limited to certain strains. This was gleaned from an investigation of the role of glycine betaine and choline in osmoprotection of a variety of strains from five genera of the Rhizobiaceae family. Glycine betaine and choline were found to be useful as osmoprotectants as both enhanced the growth of various rhizobial strains when externally provided. All rhizobial strains were also found to possess a choline uptake activity and can use choline as a carbon, nitrogen and energy source for growth.