First Advisor

Justin Courcelle

Date of Award


Document Type


Degree Name

Bachelor of Science (B.S.) in Biology and University Honors




DNA replication, DNA repair, Oxidative stress, Escherichia coli, Iron, Manganese




Reactive oxygen species (ROS) are generated through regular aerobic metabolism and iron-catalyzed degradation of hydrogen peroxide (Fridovich, 1995). ROS are known to induce single strand breaks (SSBs) in DNA via sugar or base modification (Lindahl, 1993), and double strand breaks (DSBs) can also occur when the replicative polymerase complex (replisome) polymerizes over oxidative lesions (Andrews et al., 2003), or when clustered oxidative lesions are misrepaired (Semenenko and Stewart, 2005; Semenenko et al., 2005). Intracellular ROS production has also been shown to increase after UV-induced and endogenous DNA damage (Rowe et al., 2008). All DNA lesions must be repaired for the progression of replication and subsequent cell division. One factor proposed to contribute in determining the ability of cells to resume replication after DNA damage is the concentration of divalent metals in medium. Here the phenotype of DNA replication following oxidative damage is expanded for contexts where the cell has access to iron or manganese, two metals capable of charging divalent metal-dependent proteins under normal and oxidative stress conditions, respectively. In this work, we measured survival, recovery, and mutagenesis of wildtype E. coli grown with iron or manganese after acute or chronic exposure to hydrogen peroxide. Our results show that although the presence of either metal tested had no effect on survival, the response of DNA replication after oxidative challenge is affected drastically by manganese; cells cultured with manganese exhibit a rapid recovery of DNA synthesis – though with low fidelity. Later assays involving mutants for RecF and translesion polymerases failed to implicate either candidate for these recovery phenotypes.


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An undergraduate honors thesis submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in University Honors and Biology & Philosophy

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