Dipicolinic acid as a secondary metabolite in Penicillium citreoviride.

ABSTRACT

Synthesis of dipicolinic acid in Penicillium citreoviride showed typical kinetics of a secondary metabolite. Its synthesis resumed during idiophase and continued through stationary phase of growth. Total duration of synthesis was 100 h at the end of which its synthesis was arrested. Production of dipicolinic acid by the cells was subject to catabolite repression by glucose and was not subject to end product inhibition by exogenously added dipicolinic acid. Unlike the bacteria, dipicolinic acid synthesis in this mold was highly sensitive to inhibition by calcium ions in the growth medium. Calcium promoted sporulation but dipicolinic acid was not found to be present in detectable amounts in mold spores. Addition of dipicolinic acid and Ca2+ completely inhibited its de novo synthesis, an effect not observed when calcium was replaced by Mg2+ When the mold was grown in the presence of calcium alone, its inhibitory effects on de novo synthesis of dipicolinic acid were expressed only after some of this metabolite was first synthesised by the producer cells suggesting that the active feedback inhibitor is probably a Ca dipicolinic acid complex. It is suggested that over-production of this metabolite is very important to the mold in increasing its survival potential in nature by retrieving the essential minerals from the environment through ligand metal complex at a time when cells are in the process of dying, so that a proper mineral balance is maintained within the cells.