~10¹³-10¹⁴ bacteria + archaea + fungi + viruses colonising mammalian GI tract. Contributes ~150× host gene count; synthesises vitamins B/K, short-chain fatty acids; trains immunity; influences behaviour.
~10¹³-10¹⁴ bacteria + archaea + fungi + viruses colonising mammalian GI tract. Contributes ~150× host gene count; synthesises vitamins B/K, short-chain fatty acids; trains immunity; influences behaviour.