Arginine-derived polyketides (arginoketides) produced by Streptomyces mediate interactions with fungi from Aspergillus and Penicillium genera, triggering the production of natural products. Notably, azalomycin F from Streptomyces iranensis activates the orsellinic acid gene cluster in Aspergillus nidulans. Arginoketides, found globally, impact microbial community structure by inducing fungal secondary metabolite production.