Division competence in Tetrahymena: Determination of minimum cell volume and rate of nutrient uptake

Abstract

Cell volume and doubling time have been determined for exponentially growing Tetrahymena pyriformis cells in broth medium with and without glucose and in media made from these media by dilution with water. The cells tolerate media with dry weights from 105 down to 0.06 g/L. In the diluted media the cells have small volumes and the doubling time is increased. When the cell volume increase per time per cell in a given medium is expressed as a function of the cell volume in this same medium, a direct proportionality is found. From this equation the minimum cell volume of division competence (MVDC) can be found. It is 2,100 microns 3 for T. pyriformis at 28 degrees C. The lag period resulting from an upshift of exponentially growing cells from diluted media to more concentrated media is a function of the initial and resulting cell volumes and MVDC. The increase in cell volume per unit of time for a given cell depends on the dry weight of the medium. This parameter can be transformed to mass increase per cell surface area per time, which represents rate of nutrient uptake. When plotted against the dry weight of the media, a Michaelis-Menten-like curve is obtained with two Km values of 3.8 and 0.08 g/L with corresponding Vmax values of 20 and 4 ng/cm2.s. The low Km value (0.08 g/L) indicates that Tetrahymena is able to take up nutrients from highly diluted media. The high value of Vmax (20 ng/cm2.s) increases the ability of growth in more concentrated media.(ABSTRACT TRUNCATED AT 250 WORDS)

On the Correlation of the Volume of a Prolate‐Spheroidal Cell, Tetrahymena as Determined by Electronic Particle Counters and by Morphometry

“…The attempts were unsuccessful, mainly because of uncertainties in the volume difference between individual channels of the Channelyzer and lack of appropriate large-sized calibration particles. A newer model of Coulter particle counters, the Multisizer, has extended electronics and provides a value for individual channels; moreover, this instrument has been used recently [ 1,2] to study volume changes of Tetrahymena grown in media of different organic contents. In these and other studies, the electronic MCV of Tetrahymena is underestimated [ l , 2, 4, 10-121 as compared to the volume calculated from optical measurements [e.g.…”