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要旨

Author Summary 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.