Three miles beneath the ocean's surface, where light and warmth are strangers, a community of bacteria has been quietly performing chemical work that science only now recognizes. Researchers have discovered that PVC superphylum bacteria — long overlooked in deep-sea studies — carry specialized enzymes capable of dismantling complex polysaccharides, the carbon-rich molecules that drift down from sunlit waters above. Sampled across cold seeps, hydrothermal vents, and seamounts in 2018 and 2022, these microbes reveal that the ocean's carbon cycle has hidden architects, and that our accounting of