CLONING AND DISRUPTION OF A FRAGMENT OF STREPTOMYCES-HALSTEDII DNA INVOLVED IN THE BIOSYNTHESIS OF A SPORE PIGMENT

A 5.2-kb BamHI fragment of Streptomyces halstedii was cloned by homology to the actI-carrying fragment which codes for part of the actinorhodin polyketide synthase of Streptomyces coelicolor A3(2). Gene disruption using the integrative plasmid vector, pGM160, and gene replacement experiments using a fragment mutated by introducing a cassette containing the gene encoding thiostrepton resistance, showed that the alteration of this region in the chromosome of S. halstedii caused sporulating colonies to remain white instead of taking on the typical green colour of sporulating wild-type colonies. This suggests that this fragment is involved in the biosynthesis of a spore pigment. In addition, the BanHI fragment complemented the whiE mutation of S. coelicolor C107 which confers to this mutant a white phenotype, indicating that both pigments could have a similar biosynthetic origin.