SPECIFICITY OF THE SALT REQUIREMENT OF HALOBACTERIUM CUTIRUBRUM

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Abstract
The response of the extreme halophile, Halobacterium cutirubrum, to suspension in graded concentrations of various salts was examined. Decrease in turbidity, release of cell constituents, and morphological alterations were used as measures of damage to cells. Sodium chloride, MgCl2, CaCl2, or CH3COONa in concentrations of 3.5 M or higher were required to maintain the cells as rods, while much less concentrated solutions of the salts prevented gross release of cytoplasmic constituents. The requirement for salt was not solely a requirement for a suitable osmotic pressure. The salts which replaced NaCl in maintaining cellular integrity appeared to function on the basis of a mole for mole replacement of sodium ion by the cation. No evidence was found for differential release of large (nucleic acids) or small (inorganic phosphate) molecules when bacteria were suspended in decreasing concentrations of NaCl or MgCl2. A number of salts preserved cellular integrity of H. cutirubrum, but high concentrations of NaCl were essential for growth of the bacterium.