世界上最高的山峰是珠穆朗玛峰，最深的海沟是马里亚纳海沟。人类曾多次征服过珠穆朗玛峰，但在马里亚纳海沟面前，人类显得弱小又无助。马里亚纳海沟由两个地质构造板块（菲律宾海板块和太平洋板块）碰撞挤压形成。拥有地球上已知的最深海域，达11,000米深的挑战者深渊。到了1000米，这里已经漆黑一片，生活的生物大多没有眼睛，有些还进化出来发光器官；到达3000米时，如果没有装备保护，普通人会立刻被水压挤碎骨头，骨骼碎片刺入内脏引发内出血和严重的全身粉碎性骨折；马里亚纳海沟 4829米深处的动物（图片来源：www.australiangeographic.com.au）当到达8200米时，这里是理论上的生命禁止线。在这条线的上方生活着世界上最深处的鱼类太古蜗牛鱼，它可以承受8143米的水压，相当于1600头大象踩在它身上；再向下，除了高压，还有马里亚纳海沟最深处传来的滚滚热浪。这里是最接近地核的区域。受限于技术，对深渊极端生态环境的研究，特别是马里亚纳海沟的生物圈，遭遇了较大挑战。学界对马里亚纳海沟沉积物中完整生物圈结构和微生物代谢功能知之甚少，更缺乏微生物群体的基因组序列草图。同时，学界也对马里亚纳海沟沉积物中真核微生物群落和可能存在的海洋病毒一无所知。2016年12月至2017年1月，合作团队等利用“张謇”号海洋科学考察船，对马里亚纳海沟挑战者深渊开展了海洋物理、海洋化学、海洋生物的综合生态调查研究。合作团队对采集的马里亚纳海沟沉积物标本，利用深度宏基因组分析和大规模微生物培养分离等方法，首次揭示了地球最深海洋沉积物的完整生物圈，包括细菌、古菌、真核微生物和病毒的生物群落结构、基因组序列草图和代谢生物化学潜能。Composition and phylogenetic diversity of the microbial community in the Challenger Deep sediment habitat. AThe relative sequence abundance of dominant microbial groups (top 30). B Phylogenetic analysis of the 178 MAGs based on 43 conserved single-copy, protein-coding marker genes using the maximum likelihood algorithm. Bootstrap values based on 1000 replications are shown for each branch. The scale bar represents 0.1 amino acid substitution per positionHeat-map presentation of genomic features and metabolic potential for the 178 MAGs (with the taxonomic assignment) reconstructed for the Challenger Deep sediment microbiome. Key genes involved in carbohydrate degradation (CAYzme), CO2 fixation, aerobic respiration, anaerobic respiration, and chemolithotrophy are illustrated (refer to Additional file 7: Table S7 for details). Abbreviations: GH, glycosidases or glycosyl hydrolases; PL, polysaccharide lyases; CE, carbohydrate esterases; GT, glycosyltransferases; AA, auxiliary activities; CBM, carbohydrate-binding modules; WL, Wood-Ljungdahl pathway; CBB, Calvin-Benson-Bessham cycle; rTCA, reverse tricarboxylic acid cycle; 3-HP: 3-hydroxypropionate bi-cycle; 3-HP/4-HB cycle, 3-hydroxypropionate/4-hydroxybuty rate cycleComposition of microeukaryotic community, and metabolic functions of the dominant fungal groups in the Challenger Deep sediment habitat. A The relative sequence abundance of different eukaryotic groups within total eukaryotes. B Phylogenetic relationship of major fungal groups identified in the hadal habitat, and the profiles of a carbohydrate-active enzyme family (CAZymes) and peptidase family genes. The numbers of genes detected are denoted by shade intensity. Abbreviations: GH, glycosidases or glycosyl hydrolases; PL, polysaccharide lyases; CE, carbohydrate esterases; GT, glycosyltransferases; AA, auxiliary activities; CBM, carbohydrate-binding modules. C Metabolic potentials of carbon, nitrogen, sulfur, and iron metabolism shown for the six dominant fungal groups. The presence of genes within the metabolic pathways is denoted for each group by the fan areas with color for the corresponding phylum. Gene symbols and metabolites are labeled with the KEGG designation (refer to Additional file 1: Table S8 for details).Diversity of metavirome, virus-host association, and viral genome annotation. A The relative abundance of dominant virus groups within metavirome. B Phylogenetic analysis of Caudovirales based on TerL using the maximum likelihood algorithm. Reference viral sequences from NCBI are colored in black. Scale bar, one amino acid substitution per site. The same tree with detailed labeling is provided in Fig. S3 (Additional file 17: Fig. S3). CVisualization of the virus-host association network. Diamonds and circles denote marine viruses and microbial hosts, respectively. Association is summarized between a virus family and a microbe class, represented by a linked grey line. D Annotation of viral genomes. COG annotation was performed using eggNOG-mapper [51]. AMGs related to carbohydrate metabolism are illustrated in the inner panel此外，合作团队还利用24种不同类型微生物培养基，开展了马里亚纳海沟沉积物标本在不同条件下（4/28；有氧/厌氧）的大规模微生物培养分离，共分离到超过2000株极端生态环境的细菌和真菌，共鉴定了1070种细菌和19种真菌，发现了至少19个来源于马里亚纳海沟的细菌新物种和3个真菌新物种。高压培养测试证实了它们的耐压特性，它们为马里亚纳海沟沉积物的极端环境微生物生长、生理和代谢研究提供了重要的物质基础。
Genome Biol. 2021; 22: 207.
Published online 2021 Jul 13. doi: 10.1186/s13059-021-02408-w
