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J Bacteriol. 1968 April; 95(4): 1461-1468
Copyright © 1968 American Society for Microbiology. All Rights Reserved.

Effects of Salts on the Halophilic Alga Dunaliella viridis¹

^a Exobiology Division, Ames Research Center, NASA, Moffett Field, California 94035

ABSTRACT

Determinations of the salt sensitivity of enzymes extracted from the halophilic alga Dunaliella viridis revealed that pentose phosphate isomerase, ribulose diphosphate carboxylase, glucose-6-phosphate dehydrogenase, and phosphohexose isomerase were inhibited by NaCl concentrations far lower than that in the growth medium (3.75 M). The inhibition was reversible and was not prevented by preparing the extracts in the presence of salt. Potassium, lithium, and cesium chlorides were equally inhibitory. In contrast, whole cells require rather high levels of NaCl for optimal growth, whereas growth is inhibited by low levels of the other cations. The results suggest a specific mechanism for the exclusion of sodium from the interior of the cell.

² Present address: Tulane University School of Medicine, New Orleans, La. 70013.

³ Resident Postdoctoral Research Associate of the National Academy of Sciences, National Research Council.

⁴ Present address: Department of Pharmacology, Stanford University School of Medicine, Stanford, Calif. 94305.

⁵ Present address: Department of Marine Biology, University of California, Scripps Institution of Oceanography, La Jolla, Calif. 92037.

¹ Portions of this paper were presented at the IX International Congress for Microbiology, Moscow, 24 to 30 July 1966, and at the Annual Meeting of the American Society for Microbiology, New York, N.Y., 30 April to 4 May 1967.