Incorporation of amino acid carbon into prodigiosin synthesized by nonproliferating cells of Serratia marcescens.

Abstract

We investigated incorporation into prodigiosin of carbon from amino acids after addition of U-14C-amino acids to suspensions of nonpigmented, nonproliferating cells (NPC) of Serratia marcescens incubated at 25C. Biosynthesis of prodigiosin was initiated by addition of unlabeled proline (17 mM) at 0 h followed by 42.5 mM more at 14 h to promote rapid formation of the pigment. Then, 1 to 2 h later, trace amounts of various U-14C-amino acids were added. Radioactivity of prodigiosin and of protein was measured while cultures incubated for 36 h. Radioactive carbon from amino acids that caused prodigiosin biosynthesis in NPC was incorporated approximately in the order of their effectiveness for production of prodigiosin. In addition, isotope from cysteine, glycine, methionine, threonine, and, to a small extent, tyrosine was incorporated. Incorporation of carbon from other amino acids contained in casein hydrolysate was insignificant, although all contributed carbon to cellular protein. Kinetics of incorporation paralleled kinetics for formation of prodigiosin, but the amount of isotope incorporated was low, probably because of the large amount of cold proline added to cultures and because the amino acids were used for other biosyntheses in addition to pigment formation. The data established that several amino acids contributed carbon to the prodigiosin molecule, but the biosynthetic pathways that are used must still be determined.