Speaker
Description
The passage of genes from parents to offspring is a fundamental rule of heredity. However, bacteria violate this rule of strict vertical inheritance by shuttling DNA between cells through horizontal gene transfer (HGT). Common vehicles for HGT are conjugative plasmids, extrachromosomal pieces of DNA encoding the machinery for their own transfer. In addition to standard vertical transmission, genes on such plasmids can move between different strains or even different species of bacteria. This partial “uncoupling” of the evolutionary trajectory of plasmid-borne genes from the evolution of their host has interesting consequences for the ecology and evolution of mobile genes, which will be the focus of this presentation. These consequences revolve around the feature of horizontal transfer itself. I will discuss the impact that cross-species HGT has on protein evolution, focusing on a gene encoding an enzyme that degrades a common class of antibiotics, revisiting Wright’s fitness landscape metaphor in the process. The degree of topographical alignment of landscapes across different bacterial hosts can influence the nature of genetic evolution in the presence of HGT. Furthermore, such alignment affects the potential for adaptation to be distributed across different community members. I will conclude by sketching out a conceptual framework to highlight factors for consideration in the theoretical and experimental study of the evolution of mobile genes in microbial communities.
