Experimental determination of evolutionary barriers to horizontal gene transfer

Horizontal gene transfer, the acquisition of genes across species boundaries, is a major source of novel phenotypes that enables microbes to rapidly adapt to new environments. How the transferred gene alters the growth - fitness - of the new host affects the success of the horizontal gene transfer event and how rapidly the gene spreads in the population. Several selective barriers - factors that impact the fitness effect of the transferred gene - have been suggested to impede the likelihood of horizontal transmission, however experimental evidence is scarce. The

While computational approaches have been successful in describing long-term barriers to horizontal gene transfer, our experimental results identified previously underappreciated barriers that determine the fitness effects of newly transferred genes, and hence their short-term eco-evolutionary dynamics.

We found that most gene transfers result in strong fitness costs. Previously identified evolutionary barriers - gene function and the number of protein-protein interactions - did not predict the fitness effects of transferred genes. In contrast, dosage sensitivity, gene length, and the intrinsic protein disorder significantly impact the likelihood of a successful horizontal transfer.