LARGE GENOMIC REARRANGEMENTS OF THE UNSTABLE REGION IN STREPTOMYCES-AMBOFACIENS ARE ASSOCIATED WITH MAJOR CHANGES IN GLOBAL GENE-EXPRESSION

Global gene expression is dramatically altered by genomic rearrangemen ts in Streptomyces ambofaciens RP181110. Partial genome mapping of two derivatives of strain RP181110 (strains NSA205 and NSA228) revealed r earrangements located in the unstable region of the genome (deletion i n strain NSA228; deletion and amplification in strain NSA205). Compute rized comparisons of pulse-labelled proteins separated by two-dimensio nal electrophoresis have revealed numerous differences in gene express ion among the three strains during both exponential and stationary pha ses of growth: 31 proteins were absent in both mutant strains, 16 were absent only in strain NSA228,17 were absent only in strain NSA205 and 9 were found to be present or overexpressed in strain NSA205. Thus, i n spite of the scarcity of genetic markers in the unstable region and its dispensability for growth under laboratory conditions, these resul ts suggest that it includes genes which are actively expressed. Sponta neous gene amplifications, which occur frequently in this region of th e chromosome, can further activate their expression.