马里亚纳海沟的微生物群揭示生命极限与地外可能
It is the ocean’s deepest wound, a crescent-shaped gash in the western Pacific that plunges nearly 11 kilometers below the surface. The Challenger Deep, at the southern end of the Mariana Trench, has long been a magnet for explorers, yet its most revelatory inhabitants are invisible to the human eye. Here, in near-freezing darkness, under a column of water that exerts pressures over a thousand times those at sea level, a sprawling community of microorganisms thrives in the sediment, engineering their own meek but tenacious metabolism. Far from being a barren pit of crushing monotony, the trench’s microbial ecosystem is a mosaic of adaptation that challenges our fundamental assumptions about where and how life can persist—and, perhaps, where else it might already exist.
The microbes of the hadal zone, named after Hades, have evolved an arsenal of biochemical tricks that make terrestrial extremophiles look pedestrian. Many produce high concentrations of specialized chaperone proteins and compatible solutes—organic osmolytes such as ectoine and hydroxyectoine—that stabilize enzymes and cell membranes against the distorting effects of hydrostatic pressure. Their lipid bilayers are densely packed with shorter, unsaturated fatty acid chains, rendering them fluid where ordinary membranes would seize up like cold butter. More remarkable still is their metabolic flexibility: genomic surveys from recent Japanese and American deep-submergence vehicle expeditions have recovered pathways for oxidizing hydrogen, carbon monoxide, and even solid-state iron, suggesting that the foundation of the trench’s food web rests on chemolithoautotrophy rather than on decaying material from the sunlit layers above.
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