title: Degradation of cyclic diguanosine monophosphate by a hybrid two-component protein protects Azoarcus sp. strain CIB from toluene toxicity.
abstract: Cyclic diguanosine monophosphate (c-di-GMP) is a second messenger that controls diverse functions in bacteria, including transitions from planktonic to biofilm lifestyles, virulence, motility, and cell cycle. Here we describe TolR, a hybrid two-component system (HTCS), from the β-proteobacterium Azoarcus sp. strain CIB that degrades c-di-GMP in response to aromatic hydrocarbons, including toluene. This response protects cells from toluene toxicity during anaerobic growth. Whereas wild-type cells tolerated a sudden exposure to a toxic concentration of toluene, a tolR mutant strain or a strain overexpressing a diguanylate cyclase gene lost viability upon toluene shock. TolR comprises an N-terminal aromatic hydrocarbon-sensing Per-Arnt-Sim (PAS) domain, followed by an autokinase domain, a response regulator domain, and a C-terminal c-di-GMP phosphodiesterase (PDE) domain. Autophosphorylation of TolR in response to toluene exposure initiated an intramolecular phosphotransfer to the response regulator domain that resulted in c-di-GMP degradation. The TolR protein was engineered as a functional sensor histidine kinase (TolRSK) and an independent response regulator (TolRRR). This classic two-component system (CTCS) operated less efficiently than TolR, suggesting that TolR was evolved as a HTCS to optimize signal transduction. Our results suggest that TolR enables Azoarcus sp. CIB to adapt to toxic aromatic hydrocarbons under anaerobic conditions by modulating cellular levels of c-di-GMP. This is an additional role for c-di-GMP in bacterial physiology.
authors: Department of Environmental Biology, Centro de Investigaciones Biológicas-CSIC, 28040 Madrid, Spain.
authors: Zaira
authors: Z
authors: Martín-Moldes
authors: Department of Environmental Biology, Centro de Investigaciones Biológicas-CSIC, 28040 Madrid, Spain.
authors: Blas
authors: B
authors: Blázquez
authors: Department of Microbiology, University of Washington, Seattle, WA 98195-7242.
authors: Claudine
authors: C
authors: Baraquet
authors: Department of Microbiology, University of Washington, Seattle, WA 98195-7242 ediaz@cib.csic.es csh5@uw.edu mtzamarro@cib.csic.es.
authors: Caroline S
authors: 0000-0003-4450-5177
authors: CS
authors: Harwood
authors: Department of Environmental Biology, Centro de Investigaciones Biológicas-CSIC, 28040 Madrid, Spain; ediaz@cib.csic.es csh5@uw.edu mtzamarro@cib.csic.es.
authors: María T
authors: MT
authors: Zamarro
authors: Department of Environmental Biology, Centro de Investigaciones Biológicas-CSIC, 28040 Madrid, Spain; ediaz@cib.csic.es csh5@uw.edu mtzamarro@cib.csic.es.
authors: Eduardo
authors: E
authors: Díaz
mesh_terms: D020627:Azoarcus / Q000187:drug effects / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D014050:Toluene / Q000633:toxicity*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D014050:Toluene; C062025:bis(3',5')-cyclic diguanylic acid; D006152:Cyclic GMP
keywords: anaerobe; biodegradation; c-di-GMP; hydrocarbon tolerance; phosphotransfer