We use experimental evolution to study the process of evolution in ‘real-time’. The small size and fast generation times of microorganisms allows replicate populations to be propagated under controlled environmental conditions for thousands of generations. Large population sizes means that many mutations can be sampled by evolving populations, so that evolution can be rapid. Because microbes can be cryopreserved, entire populations can be saved as a living “fossil record” to be resuscitated later to investigate changes of key parameters such as fitness or diversity.
Experimental evolution using microbial systems has led to tremendous insight across general (e.g., understanding factors influencing the repeatability of evolution) and specific (e.g., the mechanisms contributing to bacterial specialization on particular resources) questions.
The effect of a particular mutation can depend on how it interacts with its genetic (epistasis) and environmental (pleiotropy) context. We make precise genetic manipulations to examine these interactions and test for patterns that might influence general patterns of adaptation.
We examine how gene expression patterns vary during evolution and between different bacterial isolates and try to context differences to fitness consequences. The plots at left show patterns of expression of the lac operon in a strain that evolved for 2,000 generations in an environment containing lactose and in its ancestor.
Evolution in fluctuating environments allows us to examine the role of trade-offs between adaptation to different environmental components in constraining eventual outcomes. Fluctuating environments are also expected to select for different kinds of genetic interactions, affecting population evolvabilty.