Figure 1: Lighting things on fire is all in a day's work.
It is well documented that low levels of antibiotics are present in both surface water sources and in soil near industrial, large-scale farms. However, very little work has been done exploring the selective pressure for the evolution of resistance at such low concentrations. It is our concern that resistance mutations can be favored in a low antibiotic environment and that such mutations may “prime” bacteria to evolve high levels of resistance. We study this phenomenon by performing evolution experiments with Escherichia coli grown in a low concentration of the antibiotic rifampicin followed later by a sudden shift to a new environment that imposes a strong selective pressure (high drug concentration). We will sequence the rpoB gene from our evolved populations to identify key resistance mutations and perform genetic engineering to confirm their effects. This work will increase our knowledge of the evolution of antibiotic resistance and as well as the unintended but potentially dangerous effects of long term selection in the presence of low levels of antibiotics.
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