We report here that (i) spirotoamides and tautomycetin (TTN) are biosynthesized in Streptomyces griseochromogenes by two distinct type I polyketide synthases (PKSs), competing for the same pool of acyl-CoA precursors, with TTN as the dominant metabolite under the fermentation conditions examined; (ii) the biosynthesis of spirotoamides and TTN are co-regulated by TtnQ, a transcriptional activator previously characterized from the ttn cluster, and cross-talk among pathway-specific regulators for secondary metabolite biosynthesis could potentially be exploited to activate cryptic gene clusters for the discovery of new natural products; (iii) spirotoamide production can be significantly increased upon inactivation of the TTN biosynthetic machinery, leading to the isolation and structural elucidation of two new analogues, named spirotoamide C (3) and D (4), together with the known spirotoamide A, none of which showed any antibacterial activity against the selected Gram-positive and Gram-negative bacteria.