We first run preliminary tests to find experimental conditions that promoted or penalised bacterial motility. Once these conditions were set, we conducted competition experiments with fluorescently-labelled, motile and non-motile bacteria in the different environments, which produced empirical estimates for the fitness, generation times and maximal population sizes of the different competitors. These estimates allowed us to build a computer model mimicking our experimental setting so that we could generate predictions on the evolution of novel behaviours that can be tested in the laboratory. Next, these predictions were tested by propagating thirty parallel experimental populations alternating between motility-promoting and motility-penalising conditions. After several weeks of evolution, single colonies were isolated, their behaviour classified, and their numbers were compared with the theoretical predictions. Some discrepancies between simulations and experimental data made us rethink our original assumptions, which lead us to propose new hypothesis that were again subjected to experimental tests. In particular, we conducted a new set of experiments to assess the number of mutational steps and possible trade-offs involved in the rewiring of the regulatory networks controlling motility. These experiments revealed that many mutational paths towards conditionally-motile phenotypes indeed exist, but also that only a few of them can be easily trodden. To gain a detailed picture of the molecular underpinnings of these mutational pathways, a collection of end-point isolates from the evolution experiments were subjected to whole-genome sequencing. In terms of dissemination, while peer-review journal articles are still in preparation, other activities have been undertaken to communicate aspects of the action to academic and non-academic beneficiaries, including scientists directly studying the evolution of environmental sensing (e.g. publication of the code in GitHub), researchers more broadly interested in evolutionary biology (e.g. speaking at major international conferences) and the general public (e.g. press interviews). Finally, over the lifetime of the action, the Fellow has engaged in activities complementary to research such as teaching, supervising and grant writing; highly-valuable assets towards a successful career as a independent researcher.
