AUTHOR=Revitt-Mills Sarah A. , Robinson Andrew 

TITLE=Antibiotic-Induced Mutagenesis: Under the Microscope

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 11 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.585175

DOI=10.3389/fmicb.2020.585175

ISSN=1664-302X

ABSTRACT=In the 1980s it was discovered that certain antibiotics induce elevated rates of mutation in bacteria. From this, an ‘increased evolvability’ hypothesis was proposed: antibiotic-induced mutagenesis increases the genetic diversity of bacterial populations, thereby increasing the rate at which bacteria develop antibiotic resistance. However, antibiotic-induced mutagenesis is one of multiple competing factors that act on bacterial populations exposed to antibiotics. Its relative importance in shaping evolutionary outcomes, including the development of antibiotic resistance, is likely to depend strongly on the conditions. Presently, there is no quantitative model that describes the relative contribution of antibiotic-induced mutagenesis to bacterial evolution. We argue that a far more complete understanding could be reached if we had access to technology that enabled us to study antibiotic-induced mutagenesis at the molecular-, cellular- and population-levels simultaneously. Direct observations would, in principle, allow us to directly link molecular-level events with outcomes in individual cells and cell populations. 
The development of novel experimental techniques, in particular new microscopy approaches, is beginning to provide new insight into these molecule-to-cell and cell-to-population linkages. In this review we highlight microscopy studies which have allowed various aspects of antibiotic-induced mutagenesis to be directly visualised in individual cells for the first time. These studies have revealed new links between error-prone DNA polymerases and recombinational DNA repair, evidence of spatial regulation occurring during the SOS response, and enabled real-time readouts of mismatch and mutation rates. Further, we summarise the recent discovery of stochastic population fluctuations in cultures exposed to sub-inhibitory concentrations of bactericidal antibiotics and discuss the implications of this finding for the study of antibiotic-induced mutagenesis. The studies featured here demonstrate the potential of microscopy to provide direct observation of phenomena relevant to evolution under antibiotic-induced mutagenesis.