期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：46
页码：13174-13179
DOI：10.1073/pnas.1615981113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceSome bacteria have a remarkable ability to grow on toxic aromatic hydrocarbons under anaerobic conditions. Although bacteria have evolved cellular mechanisms to cope with hydrocarbon toxicity, it was unclear if signal transduction systems might exist to coordinate a protective response. Here we describe a hybrid two-component system, the TolR protein, from the bacterium Azoarcus sp. strain CIB that on binding toluene and other aromatic hydrocarbons degrades intracellular cyclic diguanosine monophosphate (c-di-GMP). A drop in c-di-GMP protects cells from toluene toxicity. C-di-GMP, found universally in bacteria, is involved in diverse functions including biofilm formation and virulence. Our finding of hydrocarbon sensing and c-di-GMP degradation by TolR for purposes of modulating hydrocarbon toxicity describes an additional role for c-di-GMP in bacterial physiology. 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 {beta}-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.
