The Amoeba‐to‐Flagellate Transformation in <i>Tetramitus rostratus.</i> I. Population Dynamics*

Abstract

SYNOPSIS. Thirty to 80% of Tetramitus rostratus amoebae were induced to transform into the flagellated stage. The procedure involved growth in a dilute hydrolyzed casein medium with living Escherichia coli dispensed in microdrops approximately 0.5 mm 3 in volume and sealed in a slide‐depressionchamber. Single amoebae placed in such microdrops did not transform until growth and division had produced a population density of 100 amoebae/mm 3 . Flagellation then began and proceeded rapidly. Analysis of growth and transformation in microdrops of different sizes but with equal numbers of amoebae, or of microdrops of the same size but different numbers of amoebae, suggested that the amoebae themselves were elaborating substances into the medium which brought about their own transformation. The effects of bacteriostasis induced by a variety of antibiotics did not clearly rule out a bacterial contribution to the factors causing transformation. Osmotic effects within physiological limits did not play any demonstrable role in inducing the response. It was concluded that transformation of amoebae to flagellates involved rapid growth and subsequent undetermined changes in the medium.