Abstract
The volume distribution of a population of cells growing by binary fission is considered practically and theoretically. A mathematical model of the volume distribution of extant cells in a growing population is derived and compared to volume distributions obtained by optical means and by use of a Coulter counter. The model has the same form as distributions obtained optically, but is substantially different from those measured with the Coulter counter. An examination of the mode of operation of the Coulter counter shows that its physical configuration leads to excessive skewness in the measured distributions. The use of an hydrodynamic focusing system produces distributions which agree in form with both the theoretical model and the optically derived volume distributions. The Coulter counter has been shown to underestimate the size of ciliates. The apparent shrinkage of the cells after dilution with saline solution is thought to be due to the permiability of the cell pellicle to electrical current. The mean size of cells measured with the Coulter counter is linearly related to the size measured microscopically. A novel method of assessing the skewness of volume distributions is developed. The relationship of skewness to growth rate is determined and discussed. The relationship between the mitotic index and the growth rate is derived for the first time. The batch growth of Tetrahymena elliotti has been studied in depth, and. it has been demonstrated that no stationary phase, in the classical sense, is developed. It is shown that there is significant cell cell death in cultures of T. elliotti, particularly in relation to sparged aeration and magnetic stirring. Continuous culture of T. elliotti failed to achieve steady states, whereas other microorganisms (T. pyriformis and Klebsiella pneumoniae) came to steady state in the same apparatus.