Chemotropism of Achlya ambisexualis to Methionine and Methionyl

The chemotropic response of the water mould Achlya ambisexualis to nutrients was investigated. Among individual amino acids only methionine was active. Other amino acids were active only in combinations containing cysteine. Methionine was unique among the amino acids tested in its ability, when incorporated uniformly into the water agar substratum, to disrupt chemotropism towards an attractant mixture of amino acids. Among non-amino acid compounds tested for chemotropic activity only S-adenosylmethionine was active. Carboxyl methylation of protein was promoted by amino acid mixtures.