GENERATION OF A GENETIC-POLYMORPHISM IN CLONAL POPULATIONS OF THE BACTERIUM STREPTOMYCES-AMBOFACIENS - CHARACTERIZATION OF DIFFERENT MUTATOR STATES

In Streptomyces ambofaciens, colony pigmentation is an unstable charac ter. Very unstable mutants selected from twelve wild type (WT) subclon es of S. ambofaciens ATCC23877 were investigated. This research showed that the polymorphism in colony pigmentation had distinct features. T he first aspect is the coexistence of four types of colonies: pigmente d colonies (Pig(+)), pigment-defective colonies (Pig(col)(-)), pigment ed colonies harboring pigment-defective sectors (Pig(sec)(+)) or pigme nt-defective papillae (Pig(pap)(+)). The second feature was revealed b y the study on Pig(pap)(+), colonies. We showed that WT progeny after 14 days of growth consisted almost totally of Pig(pap)(+) colonies. Pi g(pap)(+) colonies were also found to be genetically different from ea ch other. Characterization of twelve colonies presenting more than 20 papillae (Hyperpap colonies) led to the isolation of twelve mutator st rains which produced at high frequency Pig(col)(-) and Hyperpap coloni es. Each exhibited a specific mutator phenotype and were distinct from each other. Such strains constituted a part of the polymorphism obser ved in each of the WT progeny and also generated a high variability. F inally, we showed that pigment-defective papillae were mutants and con stituted a new form of genetic instability. (C) 1998 Elsevier Science B.V. All rights reserved.