Investigating the role of fluctuations and complexity in shaping the evolutionary dynamics of laboratory populations of E coli

Abstract

In spite of the multitude of studies that deal with the effect of fluctuating environments on bacterial populations, how fluctuations and complexity (multiple stresses silmultaneously) interact with each other is poorly studied. To investigate the interactions of complexity and fluctuations, different combination selection regimes such as Simple Predictable, Simple Unpredictable, Complex Predictable, and Complex Unpredictable were designed and bacterial populations were evolved in these selection regimes for approximately 300 generations. The fitness in terms of growth rate (r) and carrying capacity (K) of these evolved populations were assayed in different novel and component environments. No significant fitness difference was detected between different selection treatments in the novel environments. However, in component environments, Simple Predictable selection treatment showed the highest fitness and Complex Unpredictable had the lowest overall fitness. In general, predictable fluctuations had higher fitness than the unpredictable fluctuations and simple selection treatments (which faced one stress at a time) performed better than the complex selection treatments (which faced two stresses at a time).