Lysis of halophilic Vibrio alginolyticus and Vibrio costicolus induced by chaotropic anions

High concentration (1.0 M) of KSCN, but not of NaSCN, induced lysis of slightly halophilic Vibrio alginolyticus and moderately halophilic Vibrio costicolus, and the decrease in absorbance of the cell suspension was complete after 30 min at 25°C. Replacement of K⁺ with Na⁺ effectively prevented the lysis by SCN⁻. K⁺ salts of NO₃⁻, Br⁻, however, induced no significant lysis. In electron micrographs, a prolonged exposure of the cells of V. alginolyticus to 1.0 M KSCN displaced the nucleoplasm to maintain close contact with the cell membranes. After 40 min of interaction, 50% of the cellular protein, 96% of RNA and 94% of DNA were recovered in the lysed cells. In contrast to lysis in hypotonic conditions, the lysis induced by KSCN is due mainly to a partial release of protein from the cells. V. costicolus was more susceptible to SCN⁻ than V. alginolyticus, whereas nonhalophilic Escherichia coli was resistant to 1.0 M KSCN. Thus, lysis by SCN⁻ is characteristic of halophilic bacteria and cell membranes of more halophilic bacteria are more susceptible to chaotropic anions. The protective effect of Na⁺ observed here was considered to be manifested by specific interactions of Na⁺ with components of cell membranes, thereby rendering their structures resistant to the action of chaotropic anions.