The Innovation Team of Deep-sea Microbial Metabolic Mechanism and Environmental Effect of TIO has made important progress in the research on the metabolic regulation mechanism of deep-sea microbial PAHs

Recently, the Innovation Team of Deep-sea Microbial Metabolic Mechanism and Environmental Effect of the Third Institute of Oceanography of the Ministry of Natural Resources (TIO) has made important progress in the research on the metabolism and regulation mechanism of deep-sea microbial polycyclic aromatic hydrocarbons. The research results were published on the authoritative academic journal "mSystems" (5-year impact factor: 7.6, JCR zone I) of the American Society of Microbiology in October 2021, with the title "An Intracellular Sensing and Signal Transmission System that Regulates the Metabolism of Polycrystallic Aromatic Hydrocarbons in Bacteria". The chief researcher Shao Zongze of the innovation team is the corresponding author of the article, and the assistant to chief researcher, Wang Wanpeng is the first author of the article.

Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic compounds with two or more benzene rings, which widely distributed in the world's oceans, land and atmosphere. PAHs can be transported through the atmosphere and spread to remote ocean areas. In deep-sea water, PAHs tend to adsorb on suspended particles and deposit to seabed sediments. In addition, submarine activities such as submarine volcanic eruption and mid ocean ridge hydrothermal activity can also produce PAHs. Therefore, PAHs can be found even in extreme marine environments such as hydrothermal areas and even deep ocean crust. Li Jiangtao of Tongji University and others reported in the journal Nature that PAHs degrading bacteria also existed in the lower crust core samples of IODP drilling (Li et al., 2020).

Although the diversity and metabolic pathways of marine PAHs degrading bacteria have been systematically studied at home and abroad, little is known about how bacteria find PAHs in the environment, how to transduce extracellular PAHs signals into cells, and drive chemotaxis, absorption and metabolism. In order to answer these questions, we took the PAHs degrading bacterium Cycloclasticus widely distributed in the marine environment as the research object, and identified the key genes involved in polycyclic aromatic hydrocarbons intracellular sensing, signal transduction and the regulation of different PAHs degradation pathways (Fig. 1). The results showed that polycyclic aromatic hydrocarbons specifically bound to dimer cycloglycosidic acid cyclase (pdgc), resulting in the production of cyclodimer GMP (c-di-GMP) (Fig. 2), and then bound to two CRP / FNR family regulatory proteins dpr-1 and dpr-2 (Fig. 3). C-di-GMP activates the transcriptional functions of dpr-1 and dpr-2, and positively regulates the gene expression of PAHs such as pyrene and phenanthrene / naphthalene. This is the first international report on the intracellular signal transduction pathway related to bacterial degradation of PAHs of the innovation team. The results are helpful to deeply understand the regulation network of bacterial hydrocarbon metabolism and its response mechanism to PAHs polluted environment.

Since 2005, we have taken the lead in studying the degradation diversity and metabolic mechanism of PAHs in the ocean and deep sea. It is found that the deep-sea bacterium Cycloclasticus is widely distributed in the deep-sea sediments, water bodies and hydrothermal environments of the Atlantic, Pacific, Arctic and Indian oceans, and is a dominant PAHs degrading bacterium (Cui et al., 2008; Dong et al., 2015; Wang et al., 2008; Wang et al., 2020). In 2021, we first analyzed the metabolic mechanism of polycyclic aromatic hydrocarbons by Cycloclasticus sp.p1, an efficient PAHs degrading bacterium isolated from Pacific deep-sea sediments, and found different metabolic pathways and key genes of naphthalene, phenanthrene and pyrene (Wang et al., 2018). The research was supported by the key project of the major research plan of "Hydrosphere Microorganism" of NSFC (91851203), the "Excellent Youth" project of NSFC (41922041) and the construction funds of innovation team.

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Fig 1. Metabolic pattern of intracellular PAHs sensing and signal transduction system regulation

Fig. 2 Interaction between intracellular sensing protein pdgc and PAHs

Fig. 3 Second messenger c-di-GMP activates transcription regulator DPRS to promote PAHs degradation


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