Abstract:A putative polyketide synthase (PKS) gene sahA was found in the Streptomyces sahachiroi genome by PCR using degenerated primers for the ketosynthase alpha(KSα) gene.The phylogenetic tree and blast analysis revealed that sahA was belonged to the type Ⅱ PKS gene family and closely related with the subgroup of spore-pigment biosynthetic PKS genes.Once sahA was disrupted by single crossover,the spores color of Streptomyces turned into white from leaden but the time of spore-forming,quantity of sporulation,UV-resistant ability of spores and azinomycin B production had no change.It demonstrated that the putative type Ⅱ PKS gene sahA might be involved in the biosynthesis of S.sahachiroi spore-pigment.