Metabolic and adaptive mechanisms of microorganisms in sediments from deep-sea manganese nodule areas revealed by Institute of Oceanography, Chinese Academy of Sciences.

　　The environmental impact of deep-sea mining has always been a topic of great concern to the international community. At present, the International Seabed Authority (ISA) 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 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 metabolic capacity of microorganisms in manganese nodule sediments in CC area, and the related results were recently published in Microbiome, an authoritative international journal of microbiology. Researchers reconstructed 179 high-quality genomes (MAGs) by deep metagenome sequencing of manganese nodule sediment samples, and classified them into 21 phyla and 1 phyla. Through the analysis of MAGs functional genes, the evidence of the role of different microorganisms in the cycle of metal, carbon, nitrogen and sulfur is put forward for the first time. The research results can provide important scientific support for the regional environmental management plan of the International Seabed Authority and the development and environmental restoration of polymetallic nodule resources in China.

　　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. It is mainly distributed in the deep-sea plain with a water depth of 4,000 to 6,000 meters, generally far from the land, and its productivity is extremely low. In the past half century, a large number of scientific organizations and teams in many countries and regions have carried out a series of environmental impact investigations and experimental studies on the possible environmental damage caused by deep-sea mining, and conducted 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, and little is known about their environmental adaptation mechanism, diversity and metabolic ability in metal nodule deposits.

　　The research results of researchers show that in these metal-rich sedimentary environments, heterotrophic and chemoautotrophic microorganisms have evolved resistance mechanisms to heavy metals, mainly 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). Iron and manganese are the two metals with the highest environmental content in sediments. Iron may be used as an extracellular electron acceptor in the electron transfer chain by microorganisms in the form of iron (Ⅲ). Manganese-oxidizing microorganisms mainly oxidize manganese (Ⅱ) to manganese (Ⅲ) or manganese (Ⅳ), and the transport of manganese ions is less, which highlights the importance of this oxidation reaction to the survival of microorganisms in energy-limited systems. Five chemoautotrophic microorganisms belonging to Thaumarchaeota or Nitrospirota were found to have potential manganese oxidation ability. The discovery of a large number of metal oxidoreductase genes, including Mn(Ⅱ) oxidase, Fe(Ⅲ) reductase, Cr(Ⅳ) reductase, As(Ⅲ) oxidase and Hg(Ⅱ) reductase, provides important genetic resources for the potential application of heavy metal bioremediation.

　　It is found that, besides oxygen and iron (Ⅲ), microorganisms mainly use nitrate as electron acceptor to obtain energy through oxidation of metals and sulfur compounds. Most of nitrate is reduced to nitric oxide and discharged into seawater. In addition, microorganisms with diverse carbohydrate enzymes (CAZymes) did not show higher community abundance. The functional analysis of dominant microorganisms further showed that they carried a higher proportion of functional genes related to metal, nitrogen and sulfur metabolism, while CAZymes was lower. Therefore, 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.

　　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 and the Pilot Science and Technology Project of China Academy of Sciences.

　　Metabolic function of dominant microbial groups in sediments from deep-sea manganese nodule area

　　Ecological function model dominated by microorganisms in sediments of deep-sea manganese nodule area

　　Related achievements and links are as follows:

　　Zhang, D?., Li, X?., Wu, Y., Xu, X., Liu, Y., Shi, B., Peng, Y., Dai, D., Sha, Z#., Zheng, J#. (2023). Microbe-driven elemental cycling enables microbial adaptation to deep-sea ferromanganese nodule sediment fields. Microbiome 11, 160. https://doi.org/10.1186/s40168-023-01601-2

　　Source: official website, Institute of Oceanography, China Academy of Sciences. Please indicate the source of information and the arrangement of marine knowledge circle.