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J. Bacteriol. doi:10.1128/JB.00933-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Identification of a gene negatively affecting antibiotic production and morphological differentiation in Streptomyces coelicolor A3(2)

State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China.; Laboratory of Microbial Metabolism, Shanghai Jiaotong University, Shanghai 200030, China.; John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK

^* To whom correspondence should be addressed. Email: tao_meifeng{at}yahoo.com.

	Abstract

SC7A1 is a cosmid with an insert of chromosomal DNA from Streptomyces coelicolor A3(2). Its insertion into the chromosome of S. coelicolor strains, causing a duplication of a ca. 40-kb segment, delayed actinorhodin antibiotic production and sporulation, implying that it carried a gene negatively affecting these processes. Subcloning of the SC7A1 insert DNA resulted in identification of an open reading frame SCO5582 as nsdA, a gene negatively affecting Streptomyces differentiation. Disruption of the chromosomal nsdA caused overproduction of spores, and of three of four known S. coelicolor antibiotics, of quite different chemical types. At least in one case (that of actinorhodin) this was correlated with premature expression of a pathway-specific regulatory gene (actII-orf4), implying that nsdA in the wild type strain indirectly repressed expression of the actinorhodin biosynthesis cluster. nsdA expression was up-regulated upon aerial mycelium initiation, and was strongest in the aerial mycelium. NsdA has a Streptomyces protein domain of unknown function DUF921 and a conserved SXR site. A site-directed mutation (S458A) in this site in NsdA abolished its function. Blast searching showed that NsdA homologues are present in some Streptomyces genomes. Outside of streptomycetes, NsdA-like proteins have been found in several actinomycetes. Disruption of an nsdA-like gene SCO4114 had no obvious phenotypic effects on S. coelicolor. The nsdA orthologue SAV2652 in S. avermitilis could complement the S. coelicolor nsdA null mutant phenotype.

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