The spectrum of compatible solutes in heterotrophic halophilic eubacteria of the family Halomonadaceae

A new family, the Hafomonadaceae, has recently been proposed for members of the genera Deleya and Halornonas. The three strains investigated, Deleya haiuphila, Halomonas elongata and Flavobacterium halmephilum (reclassified as H. hahophila), are aerobic heterotrophic micro-organisms exhibiting an extreme salt tolerance. The major organic osmoregulatory solutes of these organisms were examined using 3C-nuclear magnetic resonance spectroscopy. The relative proportions of the solutes varied with respect to salt concentration, temperature and carbon source. The recently described amino acid ectoine was found to be a dominant solute. For the first time it could be shown for halophilic eubacteria that the intracellular concentration of solutes is sufficient to balance the osmotic pressure of the medium. Thus, there is no need to postulate a hypo-osmotic cytoplasm.