Nature and Development of Membrane Systems in Food Vacuoles of Cellular Slime Molds Predatory upon Bacteria.

Hohl, Hans R. (University of Hawaii, Honolulu). Nature and development of membrane systems in food vacuoles of cellular slime molds predatory upon bacteria. J. Bacteriol. 90:755-765. 1965.-During the digestion of bacteria by the myxamoebae of cellular slime molds, systems of concentric lamellae begin to appear within the food vacuoles. Each constituent lamella is a unit membrane of 75 to 85 A thickness. A study of these lamellae in Dictyostelium discoideum and Polysphondylium pallidum reveals that most of them do not represent original membranes of the ingested bacteria but are formed mainly in two ways. (i) After swelling and partial digestion of the bacteria, the first membranes appear adjacent to pre-existing membranes, e.g., the membrane lining the food vacuole and the cytoplasmic membrane surrounding the bacterium. Progressive addition of lamellae leads to the formation of the systems of concentric lamellae. (ii) After digestion of the bacteria has proceeded to a high degree, the concentric lamellae are formed spontaneously from clouds of amorphous material through condensation and orientation of precursor material. The study shows that, in biological systems, unit membranes may be formed from amorphous material through template action of pre-existing membranes, and does not necessarily involve fusion of membrane-bound vesicles.