A model symbiosis reveals a role for sheathed-flagellum rotation in the release of immunogenic lipopolysaccharide
Caitlin A Brennan,
Jason R Hunt,
Natacha Kremer,
Benjamin C Krasity,
Michael A Apicella,
Margaret J McFall-Ngai,
Edward G Ruby
Affiliations
Caitlin A Brennan
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, United States
Jason R Hunt
Department of Microbiology, The Carver College of Medicine, University of Iowa, Iowa City, United States; Department of Internal Medicine, The Carver College of Medicine, University of Iowa, Iowa City, United States
Natacha Kremer
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, United States
Benjamin C Krasity
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, United States
Michael A Apicella
Department of Microbiology, The Carver College of Medicine, University of Iowa, Iowa City, United States; Department of Internal Medicine, The Carver College of Medicine, University of Iowa, Iowa City, United States
Margaret J McFall-Ngai
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, United States
Edward G Ruby
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, United States
Bacterial flagella mediate host–microbe interactions through tissue tropism during colonization, as well as by activating immune responses. The flagellar shaft of some bacteria, including several human pathogens, is encased in a membranous sheath of unknown function. While it has been hypothesized that the sheath may allow these bacteria to evade host responses to the immunogenic flagellin subunit, this unusual structural feature has remained an enigma. Here we demonstrate that the rotation of the sheathed flagellum in both the mutualist Vibrio fischeri and the pathogen Vibrio cholerae promotes release of a potent bacteria-derived immunogen, lipopolysaccharide, found in the flagellar sheath. We further present a new role for the flagellar sheath in triggering, rather than circumventing, host immune responses in the model squid-vibrio symbiosis. Such an observation not only has implications for the study of bacterial pathogens with sheathed flagella, but also raises important biophysical questions of sheathed-flagellum function.
