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 homolo gy to the actI-carrying fragment which codes for part of the actinorho din polyketide synthase of Streptomyces coelicolor A3(2). Gene disrupt ion using the integrative plasmid vector, pGM160, and gene replacement experiments using a fragment mutated by introducing a cassette contai ning the gene encoding thiostrepton resistance, showed that the altera tion of this region in the chromosome of S. halstedii caused sporulati ng colonies to remain white instead of taking on the typical green col our of sporulating wild-type colonies. This suggests that this fragmen t is involved in the biosynthesis of a spore pigment. In addition, the BanHI fragment complemented the whiE mutation of S. coelicolor C107 w hich confers to this mutant a white phenotype, indicating that both pi gments could have a similar biosynthetic origin.