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Background  Oxytetracycline (OTC) is a broad-spectrum antibiotic commercially produced by  Streptomyces rimosus . Despite its importance, little is known about the regulation of OTC biosynthesis, which hampered any effort to improve OTC production via engineering regulatory genes.    Results  A gene encoding a  Streptomyces  antibiotic regulatory protein (SARP) was discovered immediately adjacent to the  otrB  gene of  oxy  cluster in  S. rimosus  and designated  otcR . Deletion and complementation of  otcR  abolished or restored OTC production, respectively, indicating that  otcR  encodes an essential activator of OTC biosynthesis. Then, the predicted consensus SARP-binding sequences were extracted from the promoter regions of  oxy  cluster. Transcriptional analysis in a heterologous GFP reporter system demonstrated that OtcR directly activated the transcription of five  oxy  promoters in  E. coli , further mutational analysis of a SARP-binding sequence of  oxyI  promoter proved that OtcR directly interacted with the consensus repeats. Therefore,  otcR  was chosen as an engineering target, OTC production was significantly increased by overexpression of  otcR  as tandem copies each under the control of strong SF14 promoter.    Conclusions  A SARP activator, OtcR, was identified in  oxy  cluster of  S. rimosus ; it was shown to directly activate five promoters from  oxy  cluster. Overexpression of  otcR  at an appropriate level dramatically increased OTC production by 6.49 times compared to the parental strain, thus demonstrating the great potential of manipulating OtcR to improve the yield of OTC production.    Electronic supplementary material  The online version of this article (doi:10.1186/s12934-015-0231-7) contains supplementary material, which is available to authorized users.

microbial cell factories

Identification of a cluster-situated activator of oxytetracycline biosynthesis and manipulation of its expression for improved oxytetracycline production in Streptomyces rimosus