Sporulation-inhibitory gene in pock-forming plasmid pSA1.1 of Streptomyces azureus.

A plasmid, pSA1.1, of Streptomyces azureus elicited conjugative pocks and inhibited the sporulation of its host mycelia. pSA1.1 was studied with a kanamycin resistance gene derived from S. kanamyceticus as a selective marker. The deletion analysis and sequencing of the derivative plasmid found an open reading frame (ORF909b) that was involved in the sporulation-inhibitory function of pSA1.1 and in pock formation. The nucleotide sequences of ORF909b were compared with those of the genes registered in GenBank, but no similarity was found. However, the predicted amino acid sequence of ORF909b showed a significantly high similarity with that of the spoIIIE gene of Bacillus subtilis. This detected gene might be a new sporulation-regulatory gene in streptomycetes.