Abstract
Protective effect of ethylenediamine dihydrochloride (ED) in preventing the damage of bacterial cell membrane by L-drying was examined. A bacterium examined was Aquaspirillum metamorphum, which might be susceptible to damage of cell membrane occurring in the desiccation. Effective protection by addition of 30 mM ED into the basal suspending medium (BSM) was found on the survival of both the wild type strain and a surface layer protein-less mutant after drying. Vegetative cells of A. metamorphum IFO 13960 (wild type) were insensitive to 1% Triton X-100, however, the cells altered into being sensitive to the detergent after drying, and the alteration were prevented by addition of ED into the BSM. Analysis of lipopolysaccharide (LPS) and surface layer protein by deoxycholate-polyacrylamide gel electrophoresis (DOC-PAGE) revealed an apparent decrease in the amount of LPS of the cells dried without ED, whereas those profile of the cells dried with ED showed little decrease. The protective activity of ED was inhibited by addition of 100-300mM NaCl into the suspending medium containing 30mM ED and lost completely by addition of 1M NaCl. These results suggest that ED binds to outer membrane and stabilizes cell membrane, like as magnesium ions which have bridging and stabilizing effects on the cell membrane. The membrane stabilized can prevent from damage occurring in the desiccation.
