[Genetic mapping of unstable chloramphenicol resistance determinant in Streptomyces coelicolor A3(2)]

The results indicative of chromosomal localization of the unstable chloramphenicol resistance determinant in Streptomyces coelicolor A3(2) have been obtained. Independent mutations specifying chloramphenicol sensitivity in different strains of S. coelicolor A3(2), S18 and A617M are localized in the same region flanked by markers argA1 and cysD18 on the genetic map. Mutations restoring chloramphenicol resistance are also localized in this region. Different locations of the genetically unstable determinant of chloramphenicol resistance detected in various laboratories are discussed, in relation to the results showing that transfer to chloramphenicol sensitivity is due to a set of various rearrangements (deletions, amplifications, deamplifications, etc.), differing in separate variants.