Andres Benitez

Evolution at the molecular level has traditionally been hard to study because the effects of adaptation on an organism as revealed by changes in phenotype usually reflect subtle long-term changes to the genome. Our approach focuses on molecular adaptation targeting a specific gene in the bacterial genome using the weak link approach. The weak link method relies on focusing the power of selection onto a specific protein by replacing an essential gene with a maladapted copy. By providing a site where single mutations can have large effects on fitness gains we can predict where selection pressure will have the most effect. In an earlier study in the Shamoo lab the essential gene adenylate kinase (AK) was replaced in the thermophile Geobacillus stearothermophilus with the same gene from Bacillus subtilis, a mesophile. Because the function of AK cannot be circumvented the new strain of G. stearothermophilus is unable to survive in temperatures of above 55C, compared with the ancestral wild type bacteria, which can survive up to 70C. AK is the weak link in preventing the G. stearothermophilus strain from surviving in thermophilic conditions, so we can predict that mutations which allow the G. stereothermophilus strain to survive as temperature increases will be mutations affecting B. subtilis adenylate kinase (AKsub) stability and activity at higher temperatures.

My research will expand on previous work using the weak link method on G. stearothermophilus by investigating how different selection regimes can alter the mutational landscape for molecular adaptation of AKsub. I am focusing on altering the turbidostat temperature program to analyze how the distribution of mutants responds to changes in selection pressure.