INTRA-CYTOPLASMIC MEMBRANE SYNTHESIS IN SYNCHRONOUS CELL-POPULATIONS OF RHODOPSEUDOMONAS-SPHAEROIDES - FATE OF OLD AND NEW MEMBRANE

  • 1 January 1978
    • journal article
    • research article
    • Vol. 253  (2) , 451-457
Abstract
A nonspecific density labeling technique was employed to monitor the synthesis of intracytoplasmic membrane in synchronously dividing populations of R. sphaeroides. The intracytoplasmic membranes of cells synchronized in D2O[deuterium oxide]-based medium underwent discontinuous decreases in specific density during synchronous cell growth, following transfer to H2O-based medium. These abrupt decreases in membrane specific density occurred immediately prior to cell division and were not observed with intracytoplasmic membranes prepared from asynchronously dividing cells. Discontinuous increases in the net accumulation of cellular phospholipid were also observed during the synchronous growth of R. sphaeroides. This is to be contrasted to the continuous insertion of protein and the photopigment components of the photosynthetic apparatus into the intracytoplasmic membrane during the cell division cycle. Examination of the protein/phospholipid ratios of purified intracytoplasmic membrane preparations revealed that this ratio undergoes cyclical changes of 35-40% during a normal cycle of cell division. DNA synthesis occurred in a stepwise manner in synchronously dividing cell populations of R. sphaeroides.