The growth and partition of cell membranes during synchronized division cycle of Caulobacter crescentus

Summary The growth and division of cell membranes in Caulobacter crescentus has been studied. This microorganism divides into flagellated and stalked cells which are easily separated by centrifugation. The biosynthesis and partition of membranes was studied by labeling the proteins with ³H]-leucine and the lipids with ³²P]. The membranes were prepared from cell spheroplasts. They further purified on a sucrose gradient.The data obtained show changes of the rate of synthesis of membranes in C. crescentus during the first synchronized division cycle (110 min): the rate is faster in the first 70 min and it drops by 26% during the following 40 min. During the period of faster synthesis the flagellated cells are changing into stalked cells while doubling in size.There is also an intracellular pool of membrane precursors the quantity of which almost doubles as the rate of membrane synthesis decreases, i.e., before cell division.The macromolecules constituting the membranes are not degraded.After division, in each membrane of the two morphologically different cell types the specific radioactivity is 50% of that of the parent cell membranes.