Student: Jillian Koster
Mentor: Professor Suzanne Deschenes
Major: Biology

Sodium nitrite is a compound commonly seen in many nutritional, clinical, and industrial applications.  When sodium nitrite is dissolved in acidic solution, it forms nitrous acid (NA), which deaminates bases and leads to mispairing.  Endonuclease V (Endo V) is known to play a role in preventing NA-induced mutations. We propose that DNA mismatch repair (MMR) may play a similar role in NA-induced mutation avoidance by correcting the mispairs arising from base deamination. As a first step in testing this hypothesis, we have used two LacZ reversion strains lacking Endo V as positive controls for our NA mutagenesis studies.  Typically, these studies are performed under aerobic, saturating growth conditions.  However, MMR is likely to be minimally active under these circumstances.  In order to evaluate the role of MMR in NA mutagenesis, logarithmically growing cells are needed. Here, we describe our modifications of standard NA methods to accommodate these alternative growth conditions.  Our preliminary results indicate that strain CC102?endo V reports a higher frequency of G:C ? A:T mutations after NA exposure, consistent with earlier published reports.  Results for CC106?endo V will also be presented.  After optimizing these methods, we will continue our NA mutagenesis studies with strains lacking MMR alone or both MMR and Endo V.

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