A FUNCTIONAL ANALYSIS OF REL GENE IN ESCHERICHIA COLI

An F-prime episome carrying the rel† ‡ Abbreviations used: the bacterial nomenclature of Demerec, Adelberg, Clark & Hartman (1966) has been followed: rel+ (formerly RCstr); rel- (RCrel) (rel-1 has been used for the relaxed allele in 58-161, rel-2 for the relaxed allele in CP79 (Fiil & Friesen, 1968)); lac, utilization of lactose; arg, his, lys, met, thi, thy, requirement for arginine, histidine, lysine, methionine, thiamine, thymine; IPTG, isopropyl-β-d-thiogalactopyranoside. gene was isolated from an Escherichia coli Hfr strain which transfers this gene as an early marker. Strains heterozygotic for the rel gene were constructed and rel+ was shown to be dominant over rel-. The kinetics of expression of the stringent phenotype were determined after transfer of the F′ rel+ episome into a rel- strain. The rel+ allele is expressed immediately after transfer and the recombinants become fully stringent after 40 minutes. © 1969.