Isolation and characterization of conditional-lethal rho mutants of Escherichia coli.

Abstract

Temperature-sensitive nitA (rho) mutants of E. coli were isolated; one of them was characterized as an amber mutant. These strains show the Nit phenotype (transcription of phage X DNA independent of the Ngene) at low temperatures and are inviable at high temperatures. The mutated sites appear to be between cya and metE on the chromosome. Temperature-sensitive nitA bacteria not only permit leftward transcription of the A genome at a hi'h rate in the absence of the A Nprotein, but also allow X gro at low temperatures. At high temperatures, phages A and T4 are incapable of normal development in these cells, while growth of 17 is not affected. The production of thermally unstable rho by the nitA temperaturesensitive mutant suggests that nitA is the structural geie for rho.Studies of host mutants that specifically affect early gene expression of phage A have provided useful information on the mechanism of transcription (1-4). We have taken advantage of the Spi phenomenon (5, 6)-the fact that bacteria lysogenic for phage P2 will not permit growth of wild-type X but will allow AsusN7nin5 to multiply-to develop a method for the isolation of bacterial mutants (nit) which permit N-independent transcription of the X genome.

Premature termination of in vivo transcription of a gene encoding a branched-chain amino acid transport protein in Escherichia coli

“…Figure 1 shows that AE500 and AE501 strains demonstrate temperature-sensitive growth characteristics compared with their isogenic parental strains. The abnormally slow growth of strain AE501 was consistent with a previous report of abnormal cell growth in strains harboring the rho-112 allele when grown on minimal-salts media (14).…”

“…Phage Plvir lysates prepared with strain CGSC6108 were used to transduce the rho-112 allele into strain AE52. Because of the close linkage between rho and ilv (61% cotransducible [14]), the rho-112 allele was selected by screening Ilv-transductants for temperature-sensitive growth at 42°C to yield strain AE501. Figure 1 shows that AE500 and AE501 strains demonstrate temperature-sensitive growth characteristics compared with their isogenic parental strains.…”

RHON1 Mediates a Rho-Like Activity for Transcription Termination in Plastids of Arabidopsis thaliana

“…To test this hypothesis, we introduced RHON1 into a conditional-lethal rho mutant of E. coli termed HD152. The HD152 strain is temperature sensitive; it dies at the restrictive temperature of 42°C and survives at the permissive temperature of 37°C (Das et al, 1976;Inoko et al, 1977). As shown in Figure 6E, the HD152 strain that was transformed with RHON1 as well as with Rho could grow at both 42 and 37°C.…”

“…Currently, the (E) Complementation of the rho mutant of E. coli with RHON1. The rho mutant of E. coli (DH152) is temperature sensitive and dies at 42°C due to the loss of Rho protein but survives at 37°C (Inoko et al, 1977). Rho-GST, RHON1-GST, and GST were introduced into the DH152 strain and growth at 37 and 42°C was measured.…”

“…The transformed cells were grown in the presence of 0.4 mM b-D-1-thiogalactopyranoside. The temperature sensitivity of E. coli cells was assayed as described by Inoko et al (1977).…”