The cell membranes of a marine pseudomonad, pseudomonas BAL-31; physical, chemical, and biochemical properties

Abstract

The marine pseudomonad, Pseudomonas BAL-31, is of special interest because it is the host cell of the lipid-containing bacteriophage PM2. The preparation of Pseudomonas BAL-31 membranes and their chemical composition is described in this paper. The buoyant density of the membranes is 1.30 in CsCl and 1.24 in sucrose. Electron micrographs of the intact membrane and the isolated cell membrane fraction are presented. The membrane-bound ATPase has properties similar to mitochondrial F₁. It is Mg²⁺-dependent and not activated by Na⁺/K⁺. On the other hand, very few inhibitors of mitochondrial F₁ inhibited this enzyme, N,N'-dicyclohexylcarbodiimide being a notable exception. Alkaline phosphatase activity was present at low levels in the membrane preparation but probably is not directly associated with the plasma membrane. Succinate dehydrogenase required no divalent cation cofactor and was inhibited by malonate. NADH oxidase activity was very low relative to ATPase and succinate dehydrogenase activities. The cytochromes of the electron transport system were characterized as o₅₇₀, a₆₂₆, b₅₆₀, and c₅₅₄.