Chinese scholars reveal the microbial metabolism and adaptation mechanism of sediments in deep-sea manganese nodule area
The Institute of Oceanography of China Academy of Sciences, together with the Second Institute of Oceanography of the Ministry of Natural Resources and Huazhong Agricultural University, systematically studied the microbial metabolic capacity of manganese nodule sediments in CC area, and the related results were recently published in the international academic journal Microbiome.
The global seabed is rich in polymetallic nodule resources, and it is considered to be the most potential seabed deposit type today because of its rich strategic metals. However, these resources are mainly distributed in the deep-sea plains with a water depth of 4000~6000 meters, which are generally far from land and have extremely low productivity. The environmental impact of deep-sea mining has always been a topic of great concern to the international community. In the past half century, a large number of scientific organizations and teams in many countries and regions have carried out a series of impact investigations and experimental studies on the possible environmental damage caused by deep-sea mining, and have carried out a lot of monitoring and evaluation on the impact and recovery of benthos, especially macrobenthos. However, microorganisms inhabiting the environment of metal nodule deposits are faced with the challenge of focusing on extreme environmental conditions such as metal, oligotrophic, high pressure and low temperature, but little is known about their environmental adaptation mechanism, diversity and metabolic ability in metal nodule deposits.
At present, the International Seabed Authority is actively promoting the Regional Environmental Management Plan (REMPs). The first REMPs area is the Clarion-Clipperton Fracture Zone (CC Zone) in the Eastern Pacific Ocean, in order to protect the biodiversity and ecosystem functions of the Pacific deep-sea nodule mining target area.
The researchers reconstructed 179 high-quality genomes by sequencing the deep metagenome of manganese nodule sediment samples, and classified them into 21 phyla and 1 phyla. Through the analysis of these genomic functional genes, the evidence of the role of different microorganisms in the metal, carbon, nitrogen and sulfur cycle was put forward for the first time.
The results show that in these heavy metal-rich sedimentary environments, microorganisms have evolved resistance mechanisms to heavy metals, including metal oxidation and reduction catalyzed by enzymes (manganese, chromium and mercury), metal transport mediated by membrane transporters (lead), and their synergistic effects (arsenic and copper). A large number of metal oxidoreductase genes have been found, which have important potential application value in the bioremediation of heavy metals.
In this oligotrophic energy-limited system, microorganisms mainly obtain energy by oxidizing metals (mainly manganese) and sulfur compounds. In this process, most nitrate is reduced to nitric oxide and discharged into seawater. Through the analysis of dominant microorganisms, researchers found that they have a higher proportion of functional genes related to metal, nitrogen and sulfur metabolism, while the proportion of genes related to carbohydrate decomposition is very low. This shows that it is the main adaptive strategy for microorganisms to survive in manganese nodule sediments by using inorganic nutrients (rather than organic nutrients) to obtain energy through redox reaction. Based on the above research, the researchers put forward a model of microbial ecology in sediments of manganese nodule area. The research results can provide important scientific support for the regional environmental management plan of the International Seabed Authority and the national polymetallic nodule resource development and environmental restoration.
Associate researcher Zhang Dechao from Institute of Oceanography of China Academy of Sciences and Dr. Li Xudong from Huazhong Agricultural University are co-first authors, while researcher Sha Zhongli from Institute of Oceanography of China Academy of Sciences and Professor Zheng Jinshui from Huazhong Agricultural University are co-authors. The research was supported by the National Natural Science Foundation of China and the Pilot Project of China Academy of Sciences.
Article link: https://doi.org/10.1186/s40168-023-01601-2
(Popular Daily client reporter Bo Keguo correspondent Wang Min reports)
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