Influence of Na⁺ on Synthesis of Macromolecules by a Marine Bacterium

Abstract

Resting cells of Vibrio natriegens acquired the ability to take up ¹⁴C-labeled mannitol in media containing Na⁺ and K⁺. But, the cells took up a significant quantity of the label as well in the presence of 0.3 m K⁺ and no Na⁺. The label was distributed throughout the cells in both systems. Cells incubated in mannitol minimal culture medium proliferated and synthesized approximately nine times as much protein in the presence of Na⁺ and K⁺ as those incubated in the presence of mannitol and 0.3 m K⁺. The bacteria did not proliferate in the absence of Na⁺. Cells incubated in medium containing mannitol and Na⁺ and K⁺ synthesized approximately twice the quantity of deoxyribonucleic acid and ribonucleic acid as those incubated in medium containing mannitol and 0.3 m K⁺ but no Na⁺. A significant amount of mannitolbinding protein was synthesized in the membranes of V. natriegens incubated in the presence of mannitol and Na⁺ and K⁺, but only a small quantity was produced in medium containing mannitol and 0.3 m K⁺ but no Na⁺. A binding fraction comprising at least two proteins (both with molecular weight near 34,000) was isolated by gel electrophoresis from other components of a K₂CO₃-extract of membrane protein from mannitol-grown cells. This binding fraction mediated phosphorylation of mannitol at the expense of either adenosine triphosphate or phosphoenolpyruvate. It was then found that mannitol-grown, but not broth-grown, cells contained nicotinamide adenine dinucleotide-linked mannitol-1-phosphate dehydrogenase. Neither contained mannitol dehydrogenase.