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

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

Author information

1
Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.

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.

PMID:
22716461
PMCID:
PMC3518419
DOI:
10.1111/j.1365-2958.2012.08109.x
[Indexed for MEDLINE]
Free PMC Article

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