The article explores the evolutionary relationship between sex and virulence in Escherichia coli. It examines how pathogenic and non-pathogenic strains of E. coli have evolved, using genetic data from a global collection of isolates. Pathogenic strains, such as enterohaemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), and Shigella, have arisen independently in multiple lineages, while other lineages contain few pathogens. Pathogenic lineages have experienced accelerated evolution, with frequent homologous recombination leading to highly virulent strains. This evolutionary process is linked to bacterial sex, as recombination increases the genetic diversity that drives virulence. The study reveals that recombination is widespread in E. coli, and that hybrid strains, which result from recombination, are often highly virulent. In contrast, avirulent isolates show less genetic admixture. The research also shows that the population structure of E. coli is complex, with multiple lineages and frequent recombination. The genetic diversity of E. coli has increased significantly over time, with a major population expansion occurring in the last 5 million years. The study uses phylogenetic and population genetic analyses to examine the evolutionary history of E. coli. It finds that the population structure of E. coli is not clonal, but rather involves frequent recombination. The results suggest that recombination plays a key role in the evolution of virulence, as it allows for the acquisition of new genes that contribute to pathogenicity. The study also highlights the importance of homologous recombination in the evolution of E. coli, as it increases genetic diversity and enables the adaptation of strains to different environments. The findings indicate that sex and virulence are closely linked in E. coli. The study suggests that virulence drives the need for more frequent recombination, as it increases the genetic diversity that allows for the adaptation of strains to different hosts. The research also shows that the evolution of virulence in E. coli is influenced by the host immune system, as strains that can evade immune defenses are more likely to survive and spread. Overall, the study provides important insights into the evolutionary mechanisms that drive the development of virulence in E. coli.The article explores the evolutionary relationship between sex and virulence in Escherichia coli. It examines how pathogenic and non-pathogenic strains of E. coli have evolved, using genetic data from a global collection of isolates. Pathogenic strains, such as enterohaemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), and Shigella, have arisen independently in multiple lineages, while other lineages contain few pathogens. Pathogenic lineages have experienced accelerated evolution, with frequent homologous recombination leading to highly virulent strains. This evolutionary process is linked to bacterial sex, as recombination increases the genetic diversity that drives virulence. The study reveals that recombination is widespread in E. coli, and that hybrid strains, which result from recombination, are often highly virulent. In contrast, avirulent isolates show less genetic admixture. The research also shows that the population structure of E. coli is complex, with multiple lineages and frequent recombination. The genetic diversity of E. coli has increased significantly over time, with a major population expansion occurring in the last 5 million years. The study uses phylogenetic and population genetic analyses to examine the evolutionary history of E. coli. It finds that the population structure of E. coli is not clonal, but rather involves frequent recombination. The results suggest that recombination plays a key role in the evolution of virulence, as it allows for the acquisition of new genes that contribute to pathogenicity. The study also highlights the importance of homologous recombination in the evolution of E. coli, as it increases genetic diversity and enables the adaptation of strains to different environments. The findings indicate that sex and virulence are closely linked in E. coli. The study suggests that virulence drives the need for more frequent recombination, as it increases the genetic diversity that allows for the adaptation of strains to different hosts. The research also shows that the evolution of virulence in E. coli is influenced by the host immune system, as strains that can evade immune defenses are more likely to survive and spread. Overall, the study provides important insights into the evolutionary mechanisms that drive the development of virulence in E. coli.