title: A novel human-infection-derived bacterium provides insights into the evolutionary origins of mutualistic insect-bacterial symbioses.
abstract: Despite extensive study, little is known about the origins of the mutualistic bacterial endosymbionts that inhabit approximately 10% of the world's insects. In this study, we characterized a novel opportunistic human pathogen, designated "strain HS," and found that it is a close relative of the insect endosymbiont Sodalis glossinidius. Our results indicate that ancestral relatives of strain HS have served as progenitors for the independent descent of Sodalis-allied endosymbionts found in several insect hosts. Comparative analyses indicate that the gene inventories of the insect endosymbionts were independently derived from a common ancestral template through a combination of irreversible degenerative changes. Our results provide compelling support for the notion that mutualists evolve from pathogenic progenitors. They also elucidate the role of degenerative evolutionary processes in shaping the gene inventories of symbiotic bacteria at a very early stage in these mutualistic associations.
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, Utah, United States of America. aclayto@gmail.com
authors.forename: Adam L
authors.initials: AL
authors.lastname: Clayton
authors.forename: Kelly F
authors.initials: KF
authors.lastname: Oakeson
authors.forename: Maria
authors.initials: M
authors.lastname: Gutin
authors.forename: Arthur
authors.initials: A
authors.lastname: Pontes
authors.forename: Diane M
authors.initials: DM
authors.lastname: Dunn
authors.forename: Andrew C
authors.initials: AC
authors.lastname: von Niederhausern
authors.forename: Robert B
authors.initials: RB
authors.lastname: Weiss
authors.forename: Mark
authors.initials: M
authors.lastname: Fisher
authors.forename: Colin
authors.initials: C
authors.lastname: Dale
mesh_terms: D000818:Animals; D001419:Bacteria / Q000235:genetics / Q000472:pathogenicity; D005075:Biological Evolution; D004755:Enterobacteriaceae / Q000235:genetics; D019143:Evolution, Molecular; D006790:Host-Parasite Interactions / Q000235:genetics*; D006801:Humans; D007313:Insecta / Q000235:genetics*; D008969:Molecular Sequence Data; D013559:Symbiosis; D014370:Tsetse Flies / Q000235:genetics / Q000382:microbiology