Lysis of Vibrio costicolus by osmotic shock.

Abstract

SUMMARY: Suspensions of the halophilic organism Vibrio costicolus lysed when subjected to sufficient osmotic shock; this was revealed as a marked fall in optical density. Organisms in the logarithmic phase of growth, grown in media containing m-NaCl, when suspended in NaCl or LiCl solutions with concentrationsm or lower lysed when the concentration was below 0·33 m: when the organisms were suspended similarly in KCl or NH4Cl solutions, lysis began at a concentration above 0·8 m. Older organisms were more resistant to lysis. Lysis was little affected by replacement of chloride by other univalent anions, by pH values from 4 to 10 or by previous incubation with 10𢄥 m-mercuric chloride. Addition of cetyltrimethylammonium bromide (200 μg./ml.) increased resistance to lysis in both NaCl and KCl solutions. Organisms grown in media of NaCl concentrations ranging from 0·5 to 3·0 m began to lyse at a NaCl concentration one-third of that present during growth. Organisms suspended in NaCl solutions of one-half the concentration in which they had been grown equilibrated promptly to the new environment; this was shown by a decrease of 50 % in the salt concentration at which lysis then began. When organisms were transferred to salt concentrations higher than that of the growth medium, the osmotic sensitivity was not affected. It is concluded that the osmotic status of these organisms is controlled chiefly by small ions or molecules which leak rapidly from the cells on transfer to dilute environments.