animal host 5,627 host-associated 5,627 digestive tract 5,620 mammalian host 5,386 intestine 5,383 human host 4,283 industrialized 3,620 adult 1,611 urban 471 rural 339 child 336 non-industrialized 303 elderly 278 rumen 213 infant 128 mouth 102 adolescent 84 hunter-gatherer 80 saliva 65 anthropogenic 56 aquatic 40 traditional agriculturalist 32 terrestrial 30 wastewater 29 sludge 26 sewage 19 anaerobic 14 agriculture 13 insect host 10 food 7 ancient microbiome 7 medium temperature 6 dairy product 6 low temperature 5 cropland 5 fresh water 4 groundwater 4 contaminated 4 built environment 4 airways 4 subsurface 4 full term birth 3 waste 3 marine 2 hospital 2 mine 1 high temperature 1 very low temperature 1 soil 1 fermented food 1