Definition: In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.
Input: Viral gain-of-function mutations are commonly observed in the laboratory; however, it is unknown whether those mutations also evolve in nature. We identify two key residues in the host recognition protein of bacteriophage l that are necessary to exploit a new receptor; both residues repeatedly evolved among homologs from environmental samples. Our results provide evidence for widespread host-shift evolution in nature and a proof of concept for integrating experiments with genomic epidemiology. Many viruses can expand their host range with a few mutations 1-3 that enable the exploitation of new cellular receptors 2,3 . Such mutations may be the first steps toward an epidemic outbreak; this observation has driven an expansion of theoretical 4 , experimental and surveillance studies of host-range shifts in emergent pathogens, including avian influenza 5-8 , coronaviruses 9,10 , HIV 11 and ebolavirus 12 . Ideally, laboratory evolution experiments could be used to accelerate our understanding of how viruses expand their host range. However, it is not clear whether viral evolution observed under the chemical and physical environments of a laboratory can faithfully inform us about viral evolution in nature, for at least two reasons. First, evolutionary trajectories might be sensitive to differences in environmental conditions between the laboratory and nature. Second, the number of evolutionary paths sampled in laboratory experiments is very small compared to natural virus diversity due to the enormous size of viral All rights reserved. No reuse allowed without permission.

Viral gain-of-function experiments uncover residues under diversifying selection in nature