在研究人类微生物组对健康和疾病的贡献时，胃肠道生态系统受到了最多的关注。这种集中精力是合乎逻辑的，因为肠道中微生物极其丰富，而且与其他器官相比取样相对容易。然而，肠道与多个肠外器官密切相连，为传统上认为无菌或仅短暂含有微生物群的器官中的稳态微生物定植和发病机制提供了机会。这些栖息地的采样具有挑战性，而且大量宿主组织中微生物生物量较低，这给研究带来了挑战。然而，最近的研究结果表明，许多与肠道密切相关的肠外器官都拥有稳定的微生物组，这些微生物组以选择性方式从肠道定殖，并强调了不仅是细菌组的影响，而且是真菌组和病毒组对肿瘤发生和发展的影响。 health.© 作者（或其雇主）2023。禁止商业重复使用。请参阅权利和权限。英国医学杂志出版。

The gastrointestinal ecosystem has received the most attention when examining the contributions of the human microbiome to health and disease. This concentration of effort is logical due to the overwhelming abundance of microbes in the gut coupled with the relative ease of sampling compared with other organs. However, the intestines are intimately connected to multiple extraintestinal organs, providing an opportunity for homeostatic microbial colonisation and pathogenesis in organs traditionally thought to be sterile or only transiently harbouring microbiota. These habitats are challenging to sample, and their low microbial biomass among large amounts of host tissue can make study challenging. Nevertheless, recent findings have shown that many extraintestinal organs that are intimately linked to the gut harbour stable microbiomes, which are colonised from the gut in selective manners and have highlighted not just the influence of the bacteriome but that of the mycobiome and virome on oncogenesis and health.© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.