A Bacillus subtilis sensor kinase involved in triggering biofilm formation on the roots of tomato plants

Mol Microbiol. 2012 Aug;85(3):418-30. doi: 10.1111/j.1365-2958.2012.08109.x. Epub 2012 Jun 20.

Abstract

The soil bacterium Bacillus subtilis is widely used in agriculture as a biocontrol agent able to protect plants from a variety of pathogens. Protection is thought to involve the formation of bacterial communities - biofilms - on the roots of the plants. Here we used confocal microscopy to visualize biofilms on the surface of the roots of tomato seedlings and demonstrated that biofilm formation requires genes governing the production of the extracellular matrix that holds cells together. We further show that biofilm formation was dependent on the sensor histidine kinase KinD and in particular on an extracellular CACHE domain implicated in small molecule sensing. Finally, we report that exudates of tomato roots strongly stimulated biofilm formation ex planta and that an abundant small molecule in the exudates, (L) -malic acid, was able to stimulate biofilm formation at high concentrations in a manner that depended on the KinD CACHE domain. We propose that small signalling molecules released by the roots of tomato plants are directly or indirectly recognized by KinD, triggering biofilm formation.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Bacillus subtilis / enzymology*
  • Bacillus subtilis / genetics
  • Bacillus subtilis / growth & development*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Biofilms*
  • Gene Expression Regulation, Bacterial / drug effects
  • Histidine Kinase
  • Lycopersicon esculentum / microbiology*
  • Malates / pharmacology
  • Models, Molecular
  • Molecular Sequence Data
  • Mutation
  • Operon
  • Phosphotransferases / chemistry
  • Phosphotransferases / genetics
  • Phosphotransferases / metabolism*
  • Plant Exudates / chemistry
  • Plant Exudates / pharmacology
  • Plant Roots / microbiology*
  • Protein Interaction Domains and Motifs
  • Protein Kinases / chemistry
  • Protein Kinases / genetics
  • Protein Kinases / metabolism
  • Sequence Alignment
  • Transcription Factors / metabolism

Substances

  • Bacterial Proteins
  • Malates
  • Plant Exudates
  • Spo0A protein, Bacillus subtilis
  • Transcription Factors
  • malic acid
  • Phosphotransferases
  • Protein Kinases
  • Histidine Kinase