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Second Genome

Meaning

The Second Genome is an evocative, conceptual term used to describe the collective, vast genetic material of the trillions of microorganisms—including bacteria, archaea, fungi, and viruses—that symbiotically inhabit the human body, predominantly within the gastrointestinal tract. This immensely complex microbial community possesses a total genetic coding capacity that substantially exceeds the human host’s own genome. The functions encoded by this “second genome” profoundly influence host physiology, metabolism, and essential endocrine function.