Abstract
The chemotactic response of the mitospores and meiospores of Allomyces macrogynus and A. abuscula to casein hydrolysate was shown to he caused by the combined action of leucine and lysine in the hydrolysate. The testing was done by counting the zoospores that attached to a membrane through which substances diffused downward. The action of leucine and lysine was shown to be synergistic and to be specific for the L, forms. The optimum concentration above the membrane was 5 × 10‐2M for each amino acid. An effect was detectable down to approximately 10‐55 M. The addition of L‐proline to the mixture increased the response. Proline in combination with leucine caused good attachment, although less than that by leucine and lysine, of the zoospores of A. arbuscula but not of those of A. macrogynus.