# Admin Supplement: Molecular basis of ionizing radiation resistance

> **NIH NIH R01** · UNIVERSITY OF WISCONSIN-MADISON · 2020 · $6,572

## Abstract

PROJECT SUMMARY/ABSTRACT
In this project, we will systematically define the genetic and cellular adaptations associated with an extremophile
phenotype in bacteria – extraordinary resistance to the effects of ionizing radiation (IR). Instead of studying
prototypical IR resistant species such as Deinococcus radiodurans, we are generating IR resistant Escherichia
coli populations by directed evolution. The resulting strains approach, and in some cases exceed the levels of
IR resistance seen in Deinococcus. Analysis of the mutations underlying the acquired phenotype will allow us to
quickly home in on the key cellular innovations. The ultimate goal is to define ALL processes and mechanisms
that contribute to an extreme IR resistance phenotype. The directed evolution of this phenotype in E.
coli provides a window that makes this possible.
 In this work we will both exploit and expand an existing resource of four highly evolved populations of E.
coli. Using directed evolution, all of these have acquired high levels of IR resistance. The populations are
designated IR-1-20, IR-2-20, IR-3-20, and IR-4-20. We have already defined the mutations most relevant to the
phenotype in both IR-2-20 and IR-3-20. In addition, we are currently generating four new evolved populations
from scratch, using a different type of radiation source, and further evolving the four existing populations. There
are four specific aims:
 Aim 1 focuses on the evolution of new and existing populations, as well as definition of the mutations that
make substantial contributions to the phenotype. Defined strains with key contributing mutations, isolated in an
otherwise wild type background, will be constructed. Aim 2 represents a general effort to use the modern
resources of systems biology to thoroughly characterize the evolved populations and single colony isolates
derived from them. Aim 3 will focus on an exploration of one particular contributing mechanism of IR resistance
involving genetic alterations in genes encoding proteins involved in replication restart. Aim 4 is the capstone. We
will use information gained from aims 1-3 to transfer the IR resistance phenotype intact by introducing a defined
set of mutations into Salmonella enterica.
 In this mentored research experience, Ms. Wolfsmith will be involved in work described under aim 2. We
now have four highly evolved populations that are nearly as resistant to IR as is Deinococcus. The sheer numbers
of mutations present provide a challenge in determining which of them is important for the IR resistance
phenotype. We can narrow things down by comparing different populations and focusing on patterns found in
two or more of them. However, that still leaves us with many dozens of prominent candidate mutations. We have
constructed large numbers of strains in which particular candidate mutations are isolated in otherwise wild type
backgrounds. We also have strains that combine some of these. All of these strains must be tested for growth...

## Key facts

- **NIH application ID:** 10144766
- **Project number:** 3R01GM112757-04S1
- **Recipient organization:** UNIVERSITY OF WISCONSIN-MADISON
- **Principal Investigator:** Michael M. Cox
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $6,572
- **Award type:** 3
- **Project period:** 2017-08-01 → 2021-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10144766

## Citation

> US National Institutes of Health, RePORTER application 10144766, Admin Supplement: Molecular basis of ionizing radiation resistance (3R01GM112757-04S1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10144766. Licensed CC0.

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