The effect of chlorides of monovalent cations, urea, detergents, and heat on morphology and the turbidity of suspensions of red halophilic bacteria.

Abstract

Suspensions of Halobacterium cutirubrum, grown and suspended in 4.0 M sodium chloride, showed on transfer to increasingly lower concentrations of sodium chloride an increase in turbidity followed by an abrupt decrease. When the suspensions were placed in potassium, rubidium, cesium, lithium, or ammonium chlorides, there was no increase in turbidity but usually a gradual decrease as the concentration of the salt is decreased. In potassium, rubidium, and cesium chlorides these changes were correlated with a change in morphology from rods, through transition forms, to spheres, similar to changes in NaCl, except that transition forms were found even at concentrations of 4.0 M. In lithium and ammonium chlorides there was an immediate change at 5.0 and 4.5 M respectively and two to five small spheres were formed from each rod. In mixtures of sodium and potassium chlorides the morphology of the cells depended on the ionic strength and concentration of sodium. Spheres were also produced by heating the cells to 60–70 °C, the time required for the conversion increasing with increasing salt concentration. In urea solutions the cells lysed, although at certain concentrations of urea and NaCl a change to small spheres was observed. Ionic detergents caused the cells to disintegrate gradually. These observations are taken as further evidence that sodium is required to maintain the cell wall of the red halophilic rods.