title: Cronobacter sakazakiiATCC 29544 Autoaggregation Requires FliC Flagellation, Not Motility.
abstract: Cronobacter sakazakiiis an opportunistic nosocomial and foodborne pathogen that causes severe infections with high morbidity and mortality rates in neonates, the elderly, and immunocompromised individuals. Little is known about the pathogenesis mechanism of this pathogen and if there are any consequences ofC. sakazakiicolonization in healthy individuals. In this study, we characterized the mechanisms of autoaggregation inC. sakazakiiATCC 29544 (CS29544). Autoaggregation in CS29544 occurred rapidly, within 30 min, and proceeded to a maximum of 70%. Frameshift mutations in two flagellum proteins (FlhA and FliG) were identified in two nonautoaggregating CS29544 clonal variant isolates. Strategic gene knockouts were generated to determine if structurally intact and functional flagella were required for autoaggregation in CS29544. All structural knockouts (ΔflhA, ΔfliG, andΔfliC) abolished autoaggregation, whereas the functional knockout (ΔmotAB) did not prevent autoaggregation. Complementation with FliC (ΔfliC/cfliC) restored autoaggregation. Autoaggregation was also disrupted by the addition of exogenous wild-type CS29544 filaments in a dose-dependent manner. Finally, filament supercoils tethering neighboring wild-type CS29544 cells together were observed by transmission electron microscopy.In silicoanalyses suggest that direct interactions of neighboring CS29544 FliC filaments proceed by hydrophobic bonding between the externally exposed hypervariable regions of the CS29544 FliC flagellin protein. Further research is needed to confirm if flagella-mediated autoaggregation plays a prominent role inC. sakazakiipathogenesis.
authors.affiliation: Department of Food Science and Human Nutrition, University of Illinois at Urbana Champaign Urbana, IL, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Hoeflinger
authors.affiliation: Department of Food Science and Human Nutrition, University of Illinois at Urbana Champaign Urbana, IL, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Miller
keywords: Cronobacter sakazakii; FliC; autoaggregation; flagella; protein-protein interactions