Borrelia burgdorferi requires the alternative sigma factor RpoS for dissemination within the vector during tick-to-mammal transmission

PLoS Pathog. 2012 Feb;8(2):e1002532. doi: 10.1371/journal.ppat.1002532. Epub 2012 Feb 16.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Borrelia burgdorferi / genetics*
  • Borrelia burgdorferi / metabolism
  • Disease Vectors
  • Ixodes
  • Lyme Disease / genetics*
  • Lyme Disease / transmission*
  • Microscopy, Confocal
  • Microscopy, Electron, Transmission
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sigma Factor / genetics*
  • Sigma Factor / metabolism

Substances

  • Bacterial Proteins
  • Sigma Factor
  • sigma factor KatF protein, Bacteria