host-associated 33,596 animal host 33,593 digestive tract 33,490 intestine 32,530 mammalian host 32,456 human host 28,859 industrialized 23,542 adult 13,257 urban 4,099 infant 3,245 child 2,855 elderly 2,258 rural 2,018 non-industrialized 1,784 mouth 1,129 adolescent 833 saliva 767 full term birth 604 rumen 459 traditional agriculturalist 429 anthropogenic 257 preterm birth 239 terrestrial 176 aquatic 167 hunter-gatherer 138 wastewater 123 built environment 104 sewage 101 airways 78 urogenital tract 48 ancient microbiome 39 insect host 39 agriculture 33 sludge 29 soil 26 hospital 21 low temperature 20 marine 20 medium temperature 19 skin 16 grassland 16 food 15 fermented food 15 wetland 14 lentic 14 paludal 14 anaerobic 11 cropland 8 very low temperature 6 fresh water 6 plant host 3 subsurface 3 low salinity 3 stream 2 ancient dental calculus 2 ice 2 high temperature 2 groundwater 2 tundra 2 contaminated 2 permafrost 1 air 1 forest 1 phyllosphere 1 mine 1 pelagic 1 waste 1