Experiments relating to the biosynthesis of bacilysin.

1. Bacilysin, a peptide which yields l-alanine and l-tyrosine on acid hydrolysis, was produced by a strain of Bacillus subtilis (A 14) in a chemically defined medium containing glucose, ammonium acetate or ammonium chloride, potassium phosphate and other inorganic salts, and ferric citrate. 2. Under the conditions used growth was diphasic. Bacilysin was formed during the second phase of slower growth, and there was little production during the stationary phase. Nevertheless, bacilysin production occurred when protein synthesis was inhibited by chloramphenicol. It thus appears that there is no obligatory coupling of protein synthesis and bacilysin synthesis. 3. When dl-[1-(14)C]alanine was added to a growing culture of B. subtilis, (14)C was incorporated into bacilysin, which contains an N-terminal alanine residue. 4. Under similar conditions virtually no (14)C was incorporated into bacilysin from dl-[2-(14)C]tyrosine, l-[U-(14)C]tyrosine or [1-(14)C]acetate, although these compounds were used by the cell for the biosynthesis of other substances. These results indicate that neither tyrosine nor acetate is a precursor of the fragment of bacilysin which yields tyrosine on hydrolysis with hot 6n-hydrochloric acid. 5. The tyrosine-yielding fragment of bacilysin was labelled with (14)C from [1,6-ring-(14)C(2)]shikimic acid. The biosynthesis of bacilysin thus appears to involve a diversion from the pathway leading to aromatic amino acids at the shikimic acid stage, or a subsequent one.