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.