Isolation and characterization of temperature-sensitive mutants of Streptomyces coelicolor A3(2) blocked in macromolecular synthesis.

A collection of temperature-sensitive mutants of Streptomyces coelicolor A3(2) was isolated. The majority of the mutants showed an osmotically remedial phenotype. Mutants defective in macromolecular synthesis were identified and characterized further. Four mutants were found in which DNA replication was defective, but which continued to synthesize RNA and protein at the restrictive temperature (39 degrees C). The kinetics of cessation of DNA synthesis allowed a tentative identification of slow (initiation) and fast (elongation) stop dna mutants. The inhibition of DNA replication in the four mutants was found to be reversible on returning to the permissive temperature (30 degrees C), but only after a delay of about 2 h. Three other mutants were identified which showed not only cessation of DNA replication at the restrictive temperature, but also defects in other macromolecular synthesis events.