The rare earth, scandium, causes antibiotic overproduction in Streptomyces spp.

Despite their importance in the chemical industry, the significance of rare earths in biology has been largely overlooked. Here, it is reported that the rare earth, scandium (Sc), causes antibiotic overproduction by 2–25-fold when added at a low concentration (10–100 µM) to cultures of Streptomyces coelicolor A3(2) (actinorhodin producer), Streptomyces antibioticus (actinomycin producer), and Streptomyces griseus (streptomycin producer). Not just for enhancement of antibiotic production, scandium was also effective in activating the dormant ability to produce actinorhodin in Streptomyces lividans . The effects of scandium were exerted at the level of transcription of pathway-specific positive regulatory genes, as demonstrated by marked up-regulation of act II-ORF4 in S. coelicolor cells exposed to this element. The bacterial alarmone, guanosine 5′-diphosphate 3′-diphosphate, was essential for actinorhodin overproduction provoked by scandium.