A study of the regulation of undecylprodigiosin biosynthesis in Streptomyces coelicolor A3(2)
Undecylprodigiosin is one of four secondary metabolites with antibacterial activity produced by S. coelicolor A3(2). The overall aim of this study was to further investigate the control of biosynthesis of the secondary metabolite undecylprodigiosin (Red) in Streptomyces coelicolor A3(2). Proline transport mutants (Put-) were isolated, and the over-production of Red was observed in these strains. It was hypothesised that Red biosynthesis is essential as a shunt for excess proline in the Put- mutants. Red biosynthesis was abolished by disrupting the redX structural gene in a Put- mutant. The Put- RedX- mutants were viable, demonstrating that Red is not essential in Pur mutants. Si nuclease mapping of redD and redX genes in a Put- mutant revealed that red genes are transcribed earlier in the growth phase of Put- mutants compared to the progenitor strain J802. Pwb (pigmented whilst bid) mutants had been isolated due to their ability to produce Red in a b1dA background. The regions believed to contain the mutations of Pwb-6, Pwb-9, Pwb-16 and Pwb+ were sub-cloned and sequence data obtained. An open reading frame was identified which is predicted to encode a protein showing homology to the UhpA-LuxR family of regulators. The open reading frame, contains an in-frame TTA codon. It is proposed that this gene, named redZ, mediates the b1dA dependence of Red biosynthesis. The Pwb-6 mutation was located to the putative -35 promoter region. The mutation makes the promoter more similar to the enteric bacterium major sigma factor promoter -35 consensus sequence. It is anticipated that greater transcription from the promoter causes the Pwb phenotype. Introduction of the Pwb-9 redZ gene into antibiotic biosynthesis mutants, absA and absB, did not result in Red biosynthesis.