Streptomyces coelicolor is one of the soil-dwelling gram-positive bacteria,which adopts a complex life cycle including vegetative mycelia,aerial mycelia and spores,and also regarded as a model for antibiotic production.We characterized SigK (SCO6520) was a typical SigB-like sigma factor of S.coelicolor by interaction with RNA polymerase core enzyme in vivo and transcription initiation from ctc promoter in vitro,sigK mutant switched from vegetative mycelia to aerial mycelia earlier than wild type on P2YE medium and showed higher expression of chpE and chpH.Loss of SigK also resulted in accelerated and enhanced production of aetinorhedin and undecylprodigiosin.