Repeatability and Contingency in the Evolution of a Key Innovation in Phage Lambda

• Published in: Science (American Association for the Advancement of Science) Vol. 335; no. 6067; pp. 428 - 432
• Main Authors: Meyer, Justin R., Dobias, Devin T., Weitz, Joshua S., Barrick, Jeffrey E., Quick, Ryan T., Lenski, Richard E.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 27.01.2012; The American Association for the Advancement of Science
• Subjects: Alleles; Bacteria; Bacterial Outer Membrane Proteins - genetics; Bacterial Outer Membrane Proteins - metabolism; Bacteriophage lambda - genetics; Bacteriophage lambda - physiology; Bacteriophages; Biological and medical sciences; Contingency; Ecological genetics; Ecology; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli - virology; Evolution; Evolution, Molecular; Evolutionary biology; Evolutionary genetics; Fundamental and applied biological sciences. Psychology; Genetic mutation; Genetics; Genome, Bacterial; Genome, Viral; Infections; Innovation; Microbial genetics; Microbiology; Mutation; Polymorphism, Single Nucleotide; Porins - genetics; Porins - metabolism; Receptors; Receptors, Virus - genetics; Receptors, Virus - metabolism; Selection, Genetic; Viral Tail Proteins - chemistry; Viral Tail Proteins - genetics; Viral Tail Proteins - metabolism; Virology; Viruses; Virus; Mutation; Phage lambda; Siphoviridae; Phage
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1214449

The processes responsible for the evolution of key innovations, whereby lineages acquire qualitatively new functions that expand their ecological opportunities, remain poorly understood. We examined how a virus, bacteriophage λ, evolved to infect its host, Eschenchia coli, through a novel pathway. Natural selection promoted the fixation of mutations in the virus's host-recognition protein, J, that improved fitness on the original receptor, LamB, and set the stage for other mutations that allowed infection through a new receptor, OmpF. These viral mutations arose after the host evolved reduced expression of LamB, whereas certain other host mutations prevented the phage from evolving the new function.This study shows the complex interplay between genomic processes and ecological conditions that favor the emergence of evolutionary innovations.