Escherichia coli mutants in which transcription is dependent on recA function.

A gene essential for viability in recA mutants of Escherichia coli K-12 was identified. This gene, rdg for recA-dependent growth, is near 16 min on the E. coli chromosome between phr and gltA and is 90% cotransduced with gltA. In a strain with an rdg deletion and the temperature-sensitive recA allele, recA200, growth stopped within 7 min after cells were shifted to the nonpermissive temperature (42 degrees C). The cells remained viable for many hours at 42 degrees C. The defect at the nonpermissive temperature is in ribonucleic acid synthesis, which was completely shut off within 20 min after the temperature shift. Protein synthesis was also shut off, but deoxyribonucleic acid synthesis continued for at least 2 h after the shift. The rdg mutation alone had no apparent effect on growth, deoxyribonucleic acid repair, or recombination.