Functional flexibility of a type III polyketide synthase in Mycobacterium marinum

Type III polyketide synthases (T3PKSs) exhibit remarkable potential to biosynthesize a wide array of architecturally distinct and functionally important metabolites. Genes for T3PKSs widely occur in pathogenic mycobacterial genomes, with no information about their physiological significance in pathogenesis. Here, we describe the biological importance of MMAR_2190, a M. marinum (Mmar) T3PKS, with orthologs in limited pathogenic mycobacterial species. High-resolution mass spectrometry revealed distinctive cyclization flexibility of MMAR_2190 to concurrently biosynthesize alkyl-resorcinols, acyl-phloroglucinols, and alkyl-α-pyrones from a single catalytic core. Investigation of Mmar biofilms revealed significant upregulation of the mmar_2190 gene and confirmed the expression of MMAR_2190 metabolites. A mmar_2190 deficient Mmar strain showed significant defect in biofilm formation, suggesting possible roles in pathogenesis. Our studies thus unfold unique functional flexibility demonstrated by the MMAR_2190 protein to generate molecular variability.