Abstracts (first author)
Trample the weak - phenotypic and genomic evolution of Pseudomonas aeruginosa in immunocompromised hosts
Novel infectious diseases have been emerging at an alarming rate over the last few decades, with sometimes devastating consequences for public health. Prime examples include the rise of HIV or the increasing incidences of tuberculosis and MRSA. To understand the origin of these novel strains, detailed knowledge is required on the adaptive evolution underlying successful establishment and spread of emergent strains in new host populations. Both theoretical studies and occasional epidemiological reports identified host immune state as a key factor in disease emergence. However, the importance of this factor has not been studied in a rigorous experimental framework that explicitly allows for long-term evolution.
I will present the results of an evolution experiment in which Pseudomonas aeruginosa PA14 adapted to populations of immunocompetent C. elegans and immunocompromised (mutant) host strains. Phenotypic analyses revealed rapid, to a large extent parallel evolution across all treatments. Strong increases in bacterial fitness were especially observed in immunocompromised hosts, suggesting immunocompromised hosts facilitated faster bacterial adaptation. Genomic analyses confirm the observed phenotypes and the large amount of parallel evolution. However, they further revealed distinct evolutionary paths chosen by bacteria adapting to immunocompromised hosts compared to those adapting to immunocompetent hosts. These results provide important insights for the understanding of bacterial adaptation to host populations, and may assist the development of theoretical models on pathogen evolution and adaptation.