Mutations arise independently of transcription in non-dividing bacteria

Abstract

It has been proposed that transcription introduces a bias into the random process of mutation. Although this hypothesis is supported by experimental data for mutations arising during active bacterial growth, the role of transcription in mutagenesis in non-dividing bacteria is entirely hypothetical. In the present study, we tested the hypothesis of a possible role of transcription in a non-dividing E. coli K12 strain. In this strain (BD010), a mutated trpB allele (trpB9578), placed under stringent transcriptional control, was tested for the appearance of prototrophic revertants on synthetic medium lacking tryptophan. The number of phenotypic revertants which appeared in the absence of trp transcription was compared to that observed when the mutated gene was continuously transcribed. Our results showed that transcription of trpB is not mutagenic under conditions of tryptophan starvation, and that the frequency of TrpB+ reversion is solely a function of the duration of starvation.

Stress-Induced Mutagenesis

“…Adaptive mutation to Lac + during stationary phase was not increased by inducing transcription of the lac operon with the gratuitous inducer IPTG (80). In another study, reversion to Trp + in E. coli increased during tryptophan deprivation even in the absence of transcription of the target gene (12). Error-prone DNA synthesis has been linked to transcription in a pathway called transcription-coupled translesion synthesis (51).…”

Stress-Induced Mutagenesis in Bacteria

“…Revertants of a histidine auxotrophy did not accumulate when Salmonella typhimurium cells were incubated in the absence of histidine (Hughes et al, 1997). In one case, the number of Trp + revertants increased during starvation of E. coli for tryptophan in the absence of transcription of the gene (Barionovi et al, 2003). Clearly more research is needed before the impact of transcription on mutation rates is understood.…”