Genotypic and phenotypic adaptation of pathogens lesson from the genus BordetellaLinz, Bodo; Ma, Longhuan; Rivera, Israel; Harvill, Eric T.Current Opinion in Infectious Diseases: June 2019 - Volume 32 - Issue 3 - p 223–230 doi: 10.1097/QCO.0000000000000549 PATHOGENESIS AND IMMUNE RESPONSE: Edited by Dennis L. Stevens and Dimitri A. Diavatopoulos Buy SDC Abstract Author InformationAuthors Article MetricsMetrics Purpose of review To relate genomic changes to phenotypic adaptation and evolution from environmental bacteria to obligate human pathogens, focusing on the examples within Bordetella species. Recent findings Recent studies showed that animal-pathogenic and human-pathogenic Bordetella species evolved from environmental ancestors in soil. The animal-pathogenic Bordetella bronchiseptica can hijack the life cycle of the soil-living amoeba Dictyostelium discoideum, surviving inside single-celled trophozoites, translocating to the fruiting bodies and disseminating along with amoeba spores. The association with amoeba may have been a ‘training ground’ for bacteria during the evolution to pathogens. Adaptation to an animal-associated life style was characterized by decreasing metabolic versatility and genome size and by acquisition of ‘virulence factors’ mediating the interaction with the new animal hosts. Subsequent emergence of human-specific pathogens, such as Bordetella pertussis from zoonoses of broader host range progenitors, was accompanied by a dramatic reduction in genome size, marked by the loss of hundreds of genes. Summary The evolution of Bordetella from environmental microbes to animal-adapted and obligate human pathogens was accompanied by significant genome reduction with large-scale gene loss during divergence. Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA Correspondence to Dr Bodo Linz, Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 501 D.W. Brooks Dr, Athens, GA 30602, USA. Tel: +1 814 4098090; e-mail: Bodo.Linz@uga.edu Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.