Anaerobically Grown Escherichia coli Has an Enhanced Mutation Rate and Distinct Mutational Spectra

Authors:
Open Access
Publisher website
Google Scholar
Abstract
Oxidative stress is a major cause of mutation but little is known about how growth in the absence of oxygen impacts the rate and spectrum of mutations. We employed long-term mutation accumulation experiments to directly measure the rates and spectra of spontaneous mutation events in Escherichia coli populations propagated under aerobic and anaerobic conditions. To detect mutations, whole genome sequencing was coupled with methods of analysis sufficient to identify a broad range of mutational classes, including structural variants (SVs) generated by movement of repetitive elements. The anaerobically grown populations displayed a mutation rate nearly twice that of the aerobic populations, showed distinct asymmetric mutational strand biases, and greater insertion element activity. Consistent with mutation rate and spectra observations, genes for transposition and recombination repair associated with SVs were up-regulated during anaerobic growth. Together, these results define differences in mutational spectra affecting the evolution of facultative anaerobes. When organisms are exposed to different environments, the rates and types of mutations that spontaneously arise in each environment can vary due to differing mutagenic pressures imposed by each environment, and these can potentially influence the evolution of the organism. Little is known about the types of mutations that arise when facultative anaerobes are grown in the absence of oxygen. To investigate the effect of oxygen availability on spontaneous mutation at the genome level, we directly measured the mutation rates of bacteria that were grown with and without oxygen under controlled laboratory conditions. To our knowledge, we have obtained the most comprehensive mutation rate estimate of anaerobically grown Escherichia coli, where mutation rates are higher in the absence of oxygen. We found that genomic structural variations, a class of mutations that are typically not investigated due to technical difficulties, were more prevalent under anaerobic growth conditions. We also identified distinct DNA strand biases for substitution types under aerobic and anaerobic growth conditions. Our findings provide new insights into the impact that oxygen availability may have on spontaneous mutations, and the mutational processes that underlie them.
Funding Information
  • Marsden Fund (AGR0902)
  • Massey University (PhD Scholarship)

This publication has 97 references indexed in Scilit: