DNA replication in Escherichia coli: Replication in absence of protein synthesis after replication inhibition

Abstract

Listen

Translate article

In Escherichia coli, DNA replication can occur in the absence of protein synthesis after a period of replication inhibition. Such replication will occur after thymine starvation, nalidixic acid treatment or exposure of a DNA temperature-sensitive mutant to a period at the non-permissive temperature. In all cases, subsequent DNA replication continued in the absemce of protein synthesis for many hours. This DNA synthesis could be observed only under conditions in which the restrictive breakdown of unmethylated cellular DNA is prevented. DNA-DNA hybridization experiments indicated that the entire bacterial genome is replicated. It was also found that DNA is synthesized sequentially and that only a portion of the chromosomes are involved in replication at any time. These appear to be chosen at random from the accumulating chromosome pool. Once acquired, this ability to synthesize DNA in the absence of protein synthesis was stable and could be maintained during growth in a complete medium which allowed synthesis and cell division. The ability to replicate DNA in the absence of protein synthesis appears to involve some normal component of the replication apparatus, since conditional lethal mutants exist which are unable to synthesize DNA at a non-permissive temperature and are altered in the ability to synthesize DNA in chloramphenicol after thymine starvation. The mechanism of stabilization of DNA replication which follows the inhibition of DNA synthesis is discussed in relation to the normal initiation and replication of the E. coli chromosome.