BIOSYNTHESIS OF BRANCHED-CHAIN FATTY ACIDS: IV. FACTORS AFFECTING RELATIVE ABUNDANCE OF FATTY ACIDS PRODUCED BY BACILLUS SUBTILIS

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Abstract
The fatty acids produced by Bacillus subtilis may be grouped into four pairs: 12-methyltetradecanoic and 14-methylhexadecanoic acids (anteiso-C15and anteiso-C17), 13-methyltetradecanoic and 15-methylhexadecanoic acids (iso-C15and iso-C17), 12-methyltridecanoic and 14-methylpentadecanoic acids (iso-C14and iso-C16), and myristic and palmitic acids (n-C14and n-C16). Any one of the branched-chain amino acids, L-isoleucine, L-leucine, or L-valine, or of the branched short-chain fatty acids, α-methylbutyrate, isovalerate, or isobutyrate, added to the glucose – yeast extract medium increased the synthesis of the specific pairs of fatty acids structurally related to the added substrate and decreased the synthesis of other fatty acids. This indicates that the relative abundance of branched-chain fatty acids in B. subtilis is a function of the relative availability of the precursors of the terminal portions of the fatty acids, presumably α-methylbutyryl-CoA, isovaleryl-CoA, and isobutyryl-CoA. This mechanism is consistent with the relative abundances of branched-chain fatty acids found in mutants of B. subtilis which require particular branched-chain amino acids. The biotin content of the culture medium and the length of incubation time also affected the relative abundance of the fatty acids.