Relation of inorganic ions to the maintenance of the integrity of the cell envelope of gram-negative marine bacteria.

Twenty-three marine and two terrestrial gram-negative bacteria were examined by electron microscopy for the effect on the outer membrane of the cells of washing the organisms successively in 0.5M NaCl and 0.5M sucrose. Six marine bacteria lost their outer membranes completely, three lost large segments but not all of their outer membranes, and six retained their outer membranes but with either gross distortions of the outer membrane and/or segments of outer membrane removed from some cells. The remaining eight marine and two terrestrial bacteria appeared to have continuous outer membranes after application of the wash procedure.Eighteen of the twenty-three marine bacteria employed in the wash treatment study and two terrestrial bacteria were examined for the effect of washing and suspending the organisms in various solutions with respect to lysis of the cells and Optical Density (O.D.) changes of suspensions.A spectrum of lytic susceptibility was observed among the marine bacteria ranging from those organisms which lysed in distilled water after exposure to Mg('2+) through organisms which lysed upon suspension in distilled water after pre-exposure to NaCl but which failed to lyse in distilled water if pre-exposed to Mg('2+) to organisms which failed to lyse in distilled water even after exposure to NaCl. E. coli and Ps. aeruginosa also fell within this spectrum.After exposure to NaCl and subsequent suspension of these organisms in decreasing concentrations of either NaCl, KCl or MgCl(,2), concentrations of KCl two to three times that of NaCl or ten to four hundred times that of MgCl(,2) could protect most marine organisms from lysis or larger decreases in the O.D. of their suspensions. However, three marine and both terrestrial bacteria required only equal concentrations of KCl or NaCl to effect protection.No overall distinction can therefore be made between marine and terrestrial bacteria with respect to the status of the outer membrane of these organisms after washing them in NaCl and sucrose solutions or the sensitivity of the two groups of organisms to lysis in distilled water after pre-exposure to NaCl or MgCl(,2)