title: Borrelia burgdorferi requires the alternative sigma factor RpoS for dissemination within the vector during tick-to-mammal transmission.
abstract: While the roles of rpoS(Bb) and RpoS-dependent genes have been studied extensively within the mammal, the contribution of the RpoS regulon to the tick-phase of the Borrelia burgdorferi enzootic cycle has not been examined. Herein, we demonstrate that RpoS-dependent gene expression is prerequisite for the transmission of spirochetes by feeding nymphs. RpoS-deficient organisms are confined to the midgut lumen where they transform into an unusual morphotype (round bodies) during the later stages of the blood meal. We show that round body formation is rapidly reversible, and in vitro appears to be attributable, in part, to reduced levels of Coenzyme A disulfide reductase, which among other functions, provides NAD+ for glycolysis. Our data suggest that spirochetes default to an RpoS-independent program for round body formation upon sensing that the energetics for transmission are unfavorable.
authors.affiliation: Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Star M
authors.initials: SM
authors.lastname: Dunham-Ems
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Caimano
authors.forename: Christian H
authors.initials: CH
authors.lastname: Eggers
authors.forename: Justin D
authors.initials: JD
authors.lastname: Radolf
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D025065:Borrelia burgdorferi / Q000235:genetics* / Q000378:metabolism; D004199:Disease Vectors; D018884:Ixodes; D008193:Lyme Disease / Q000235:genetics* / Q000635:transmission*; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012808:Sigma Factor / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria