Fatty acid and β‐amino acid syntheses in strains ofBacillus subtilis producing iturinic antibiotics

Iturinic antibiotics, produced by different strains ofBacillus subtilis, contain long‐chain β‐amino acids (β‐AA). The regulation of the synthesis of fatty acids (FA) and β‐AA was studied by modifying the culture medium. Addition of possible precursors, branched‐chain α‐amino acids, to the medium affected the FA and β‐AA compositions. According to this, theB. subtilis strains can be divided into two groups. The first contains the producers of mycosubtilin and bacillomycin F which synthesize a high level ofiso C16 chains; the second contains the producers of bacillomycin D, bacillomycin L and iturin which synthesize a high level ofn carbon chains. The incorporation of radioactive sodium acetate into FA and β‐AA showed rapid FA synthesis followed by a second synthetic step. Although the detailed mechanism has not yet been elucidated, this second step, corresponding to the β‐AA synthesis, seemed to be a key step in determining the alkyl chain of β‐AA.