Pulcherriminic acid biosynthesis and Transport: Insights from a heterologous system inSaccharomyces cerevisiae

Pulcherriminic acid is an iron chelator produced by someKluyveromycesandMetschnikowiayeasts. Its biosynthesis is encoded by the four–genePULcluster, wherePUL1andPUL2are the biosynthetic enzymes,PUL3mediates the uptake of iron–bound pulcherrimin, andPUL4is a putative regulator.

Pulcherriminic acid holds antifungal potential, as the growth of organisms unable to uptake pulcherrimin is inhibited by deficit of essential iron. Thus, a heterologous production system to further characterize and optimize its biosynthesis would be valuable.

Using our in–house yeast collection and genomes available in databases, we clonedPUL1andPUL2genes fromK. lactisand one of our wildMetschnikowiaisolates and built an effective production system inS. cerevisiaeable to inhibit pathogenic growth. In this context, theK. lactisgenes yielded faster pulcherriminic acid production than those from theMetschnikowiaisolate and a combinatorial approach showedPUL1to be the production bottleneck.

We further showed that Pul3 is an importer of pulcherrimin, but also mediates the export of pulcherriminic acid and that the growth of pathogens likeCandidozyma aurisand organisms encodingPUL3in their genome, previously called “cheaters”, is inhibited by pulcherriminic acid, highlighting its potential as an antimicrobial agent.