ISOLATION AND STRUCTURE DETERMINATION OF A NOVEL COMPATIBLE SOLUTE FROM THE MODERATELY HALOPHILIC PURPLE SULFUR BACTERIUM ECTOTHIORHODOSPIRA-MARISMORTUI

The halophilic phototrophic bacterium Ectothiorhodospira marismortui produces three organic osmolytes to counterbalance the osmotic pressure of the surrounding medium: glycine betaine, sucrose, and a novel compound. This new compound, which accounts for approximately 30% of the cells' compatible solutes, was isolated and identified by mass spectrometry and nuclear magnetic resonance. It was characterized as N-alpha-carbamoyl-L-glutamine 1-amide, an unusual amino acid derivative with no previous reference in the chemical literature. The relatively high cytoplasmic concentration of this compound (almost-equal-to 0.5 M) observed at all growth conditions suggests that it may serve a vital function as an osmoticum and/or protectant for Ectothiorhodospira marismortui in a saline environment.