SELECTIVE SYNCHRONIZATION OF TETRAHYMENA-PYRIFORMIS CELL-POPULATIONS AND CELL-GROWTH KINETICS DURING THE CELL-CYCLE

A selection synchronization technique based on ingestion of tantalum p articles has been applied to obtain synchronized cultures of the filte r feeding ciliate Tetrahymena pyriformis. Cell concentrations and cell volume distributions of synchronized cell populations have been monit ored for more than four average generation times. A simple curve-fitti ng method has been used to decompose the cell volume distributions of a synchronous population into two populations representing cells befor e and after cell division. In this way, the time course of the growth of an initially synchronous culture is decomposed into the growth of s uccessive generations. The data indicate that at any given time only t wo generations of cells are present in significant numbers. The measur ed cell volume distributions show that T. pyriformis has a complicated growth pattern during the cell cycle. Newborn T. pyriformis cells do not grow significantly at the beginning of the cell cycle. After the n ongrowing stage, cells start growing in a possibly exponential rate be fore cells enter into a second nongrowing stage. The second nongrowing stage lasts until cell division. The presented data demonstrate that growing cell populations can be viewed as the composite of cells belon ging to different generations. This concept has important implications for solving corpuscular models of cell growth.