Copyright © 1997, American Society for Microbiology 2-Sulfotrehalose, a Novel Osmolyte in Haloalkaliphilic Archaea

A novel 131 a-linked glucose disaccharide with sulfate at C-2 of one of the glucose moieties, 1-(2-O-sulfo-a-D-glucopyranosyl)-a-D-glycopyranose, was found to be the major organic solute accumulated by a Natrono-coccus sp. and several Natronobacterium species. The concentration of this novel disaccharide, termed sulfotre-halose, increased with increasing concentrations of external NaCl, behavior consistent with its identity as an osmolyte. A variety of noncharged disaccharides (trehalose, sucrose, cellobiose, and maltose) were added to the growth medium to see if they could suppress synthesis and accumulation of sulfotrehalose. Sucrose was the most effective in suppressing biosynthesis and accumulation of sulfotrehalose, with levels as low as 0.1 mM being able to significantly replace the novel charged osmolyte. Other common osmolytes (glycine betaine, glutamate, and proline) were not accumulated or used for osmotic balance in place of the sulfotrehalose by the halophilic archaeons. When cells encounter changed osmotic pressure due to al-terations in external NaCl, they can respond in various ways. They can accumulate inorganic cations with the appropriate counterion (organic or inorganic), transport or synthesize a neutral organic compatible solute, or use some combination o