Project

Why sex? Testing the benefits of recombination with an antibiotic-resistance enzyme

The question why so many organisms reproduce sexually is still unresolved, and has recently regained attention. Sex typically involves recombination of closely related DNA-sequences, which is a random process that may create novel beneficial allele combinations, but may also break up existing favourable genotypes. To solve this new paradox, effects of recombination should be measured across conditions and time scales and be related to the structure of the underlying fitness landscape. We propose to solve this problem by using a simple model system that offers thorough experimental control: laboratory evolution of the antibiotic-resistance enzyme TEM-1 β-lactamase. We will compare the dynamics of adaptation of the β-lactamase with and without recombination across a wide range of evolutionary conditions and time scales.

Aim

The overall aim of this project is to better understand the evolutionary role of recombination. We use a very simple model system that offers unprecedented control of key parameters: the laboratory evolution of the antibiotic-resistance enzyme TEM-1 β-lactamase. Our project has the following key objectives: 1. Identify possible benefits of recombination under a broad range of conditions and time scales. 2. Test for the role of epistasis in observed instances of recombination benefit of the fitness landscape and rerun evolution experiments for specific genotypes and conditions.

Approach

The project combines laboratory evolution experiments with the enzyme TEM-1 β-lactamase with extensive analyses of evolved alleles to study effects of recombination and their dependence on epistasis among the selected mutations. Selection is performed in the presence of the third-generation cephalosporin cefotaxime (CTX), for which TEM-1 has low activity. Our approach has three methodological components: (i) laboratory evolution, (ii) analyses of selected alleles, and (iii) study causes of observed recombination benefits.

Student Opportunities

We are open to applications for thesis projects! We have different thesis topics available, including projects with Geentics and Levels of Selection, Genetics of Adaptation, Bacteria.

  • Thesis Projects
  • Are you interested? Contact Diego.Pesce@wur.nl