Quorum sensing controls flagellar morphogenesis in Burkholderia glumae

PLoS One. 2014 Jan 8;9(1):e84831. doi: 10.1371/journal.pone.0084831. eCollection 2014.

Abstract

Burkholderia glumae is a motile plant pathogenic bacterium that has multiple polar flagella and one LuxR/LuxI-type quorum sensing (QS) system, TofR/TofI. A QS-dependent transcriptional regulator, QsmR, activates flagellar master regulator flhDC genes. FlhDC subsequently activates flagellar gene expression in B. glumae at 37°C. Here, we confirm that the interplay between QS and temperature is critical for normal polar flagellar morphogenesis in B. glumae. In the wild-type bacterium, flagellar gene expression and flagellar number were greater at 28°C compared to 37°C. The QS-dependent flhC gene was significantly expressed at 28°C in two QS-defective (tofI::Ω and qsmR::Ω) mutants. Thus, flagella were present in both tofI::Ω and qsmR::Ω mutants at 28°C, but were absent at 37°C. Most tofI::Ω and qsmR::Ω mutant cells possessed polar or nonpolar flagella at 28°C. Nonpolarly flagellated cells processing flagella around cell surface of both tofI::Ω and qsmR::Ω mutants exhibited tumbling and spinning movements. The flhF gene encoding GTPase involved in regulating the correct placement of flagella in other bacteria was expressed in QS mutants in a FlhDC-dependent manner at 28°C. However, FlhF was mislocalized in QS mutants, and was associated with nonpolar flagellar formation in QS mutants at 28°C. These results indicate that QS-independent expression of flagellar genes at 28°C allows flagellar biogenesis, but is not sufficient for normal polar flagellar morphogenesis in B. glumae. Our findings demonstrate that QS functions together with temperature to control flagellar morphogenesis in B. glumae.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Burkholderia / cytology*
  • Burkholderia / genetics
  • Burkholderia / physiology
  • Flagella / metabolism*
  • Gene Expression Regulation, Bacterial
  • Morphogenesis
  • Movement
  • Mutation
  • Protein Transport
  • Quorum Sensing*
  • Temperature

Substances

  • Bacterial Proteins

Grants and funding

This work was supported by the Creative Research Initiatives Program (2010-0018280) of the National Research Foundation of Korea. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.