Triggering the production of the cryptic blue pigment indigoidine from Photorhabdus luminescens

► Promoter exchange as simple way to induce the production of the cryptic blue pigment indigoidine from Photorhabdus. ► Heterologous expression in E. coli as another way to produce indigoidine. ► Different regulatory mechanisms for indigoidine biosynthesis in Photorhabdus and E. coli. ► Identification of genes acting as repressors in the indigoidine biosynthesis in Photorhabdus. ► Phylogenetic analysis of indC and comparative cluster analysis indicates horizontal transfer of the indigoidine biosynthesis gene cluster.