Isobaric enzymatic assays reveal depth-dependent variation in microbial ectoenzyme activities in the deepest ocean on Earth  

作　　者：Junwei CAO Jiahua WANG Hongge ZHANG Junhao DENG Binbin PAN Jiawang CHEN Li ZHANG Jiasong FANG 

机构地区：[1]College of Oceanography and Ecological Science,Shanghai Ocean University,Shanghai,201306,China [2]Ocean College,Zhejiang University,Zhoushan,316000,China [3]Laboratory for Marine Biology and Biotechnology,Qingdao National Laboratory for Marine Science and Technology,Qingdao,266237,China

出　　处：《Science China Earth Sciences》2025年第1期185-194,共10页中国科学(地球科学英文版)

基　　金：supported by the National Natural Science Foundation of China(Grant No.92251303);the Shanghai Municipal Education Commission(Grant No.2023ZKZD53);the Marine Biomedical Science and Technology Innovation Platform。

摘　　要：Microbial ectoenzymes play essential roles in the transformation and mineralization of organic matter in the ocean.However,conventional methods for measuring microbial ectoenzyme activities(MEAs)in the deep ocean under atmospheric conditions can misrepresent the metabolic activities of indigenous microbial communities.To overcome this limitation,we measured the activities of three microbial ectoenzymes(aminopeptidase,α-glucosidase,andβ-glucosidase)under both atmospheric and in situ pressure conditions in seawater collected using pressure-retaining and non-pressure-retaining samplers in the Challenger Deep,Mariana Trench.In the case of aminopeptidase andα-glucosidase,the highest isobaric MEAs were observed in the surface layer(50 m),followed by those at abyssopelagic depths(4,000–6,000 m)for aminopeptidase,hadal realm(10,903 m)forα-glucosidase,whileβ-glucosidase activity exhibited the highest value at 10,903 m.Furthermore,the isobaric MEAs in hadal waters were commonly found to be higher than the decompressed counterparts,highlighting the importance of pressure-retaining sampling and isobaric enzymatic assays.The half-saturation constant(K_(m))showed a general decreasing trend with depth,suggesting that the deep ocean microbes might have adapted to the high-pressure and oligotrophic environment by increasing their ectoenzyme's affinity to substrate.Furthermore,particle-free MEAs contribute more to the total MEAs in the deep ocean than particle-associated MEAs,suggesting the significance of cell-associated and dissolved ectoenzymes in ocean ecosystems.This study provides a foundation for future investigations of MEAs in the ocean and has important implications for understanding the dynamics of microbially mediated biogeochemical cycling in marine ecosystems.

关 键 词：Pressure-retaining sampling Microbial ectoenzyme activity Deep-sea microbes High pressure Mariana Trench 

分 类 号：P73[天文地球—海洋科学]