Chemoattraction Intetrahymena: On the Role of Chemokinesis

Chemoattraction of Tetrahymena pyriformis, strain GL, was measured during starvation and under different growth conditions. Log phase cells starved in buffer are attracted by certain amino acids, peptides, and proteins. Cysteine, methionine, and phenylalanine are attractants at 10-4 M. The peptides in proteose peptone (PP) and yeast extract (YE) are active at 10-6 M. Epidermal growth factor (EGF) is active at > 3 x 10-5 M. Among the proteins, platelet derived growth factor (PDGF) is the most active (3 x 10-8 M). Cells growing in defined medium are attracted by PP, YE, and some proteins (PDGF). Swimming speed was measured for starved cells with and without added attractants or repellents. With addition of PP the swimming speed increases from 0.42 to 0.51 mm/s., but for PDGF it is unchanged. The swimming speed of starved cells increases when the cells approach a solidified attractant (PP) as measured by the speed at a given distance. The speed of cells moving towards the attractant is higher than that of cells moving away from it. In conclusion, certain amino acids, peptides, and proteins are chemoattractants for Tetrahymena. Chemokinesis likely plays a considerable role in the case of PP (and YE), since they increase swimming speeds, whereas attraction by PDGF may involve chemotaxis.