A novel Streptomyces strain, L10, which is capable of producing natamycin, was isolated from a soil sample collected from Zhejiang province, China. On the basis of phylogenetic analysis of rpoB gene and 16S rDNA sequences, as well as phenotypic comparison, strain L10 (CGMCC 2644) is proposed to be a previously uncharacterized strain of S. chattanoogensis. By screening a cosmid library of strain L10 and primer walking, a partial sequence of scnRI and the entire sequence of scnRII were obtained, which are orthologues to the pathway-specific positive regulator genes of natamycin biosynthesis in S. natalensis. The engineered S. chattanoogensis Dl, generated by inserting an additional copy of scnRII into the chromosome of strain L10, increased its natamycin production by 3.3 fold in YSG medium and 4.6 fold in YEME medium without sucrose.

a b s t r a c tSigT is an ECF sigma factor in Streptomyces coelicolor. sigT and its putative anti-sigma factor gene rstA are located in one putative operon, and SigT could physically interact with RstA. Deletion of sigT or rstA caused accelerated morphological development and enhanced production of antibiotics, concomitant with over-expression of chpE, chpH, actII-orf4 and redD. Furthermore, SigT was undetectable after loss of rstA. These data suggested that SigT has a negative role on differentiation and that RstA negatively regulates the SigT activity through a putative antagonistic mechanism and at the post-transcriptional level.