The Polyketide Pks1 Contributes to Biofilm Formation in Mycobacterium tuberculosis

Infections caused by biofilms are abundant and highly persistent, displaying phenotypic resistance to high concentrations of antimicrobials and modulating host immune systems. Tuberculosis (TB), caused byMycobacterium tuberculosis , shares these qualities with biofilm infections. To identify genetic determinants of biofilm formation inM. tuberculosis , we performed a small-scale transposon screen using anin vitro pellicle biofilm assay. We identified fiveM. tuberculosis mutants that were reproducibly attenuated for biofilm production relative to that of the parent strain H37Rv. One of the most attenuated mutants is interrupted inpks1 , a polyketide synthase gene. When fused withpks15 , as in someM. tuberculosis isolates,pks1 contributes to synthesis of the immunomodulatory phenolic glycolipids (PGLs). However, in strains such as H37Rv with splitpks15 andpks1 loci, PGL is not produced andpks1 has no previously defined role. We showed thatpks1 complementation restores biofilm production independently of the known role ofpks1 in PGL synthesis. We also assessed the relationship among biofilm formation, thepks15/1 genotype, andM. tuberculosis phylogeography. A global survey ofM. tuberculosis clinical isolates revealed surprising sequence variability in thepks15/1 locus and substantial variation in biofilm phenotypes. Our studies identify novelM. tuberculosis genes that contribute to biofilm production, includingpks1 . In addition, we find that the ability to make pellicle biofilms is common amongM. tuberculosis isolates from throughout the world, suggesting that this trait is relevant to TB propagation or persistence.