animal host 25,348 host-associated 25,348 digestive tract 25,323 intestine 25,211 mammalian host 24,414 human host 22,202 industrialized 18,187 adult 10,260 urban 3,112 child 1,854 elderly 1,852 rural 1,650 non-industrialized 1,480 infant 1,126 adolescent 680 full term birth 285 traditional agriculturalist 268 anthropogenic 160 rumen 145 aquatic 115 wastewater 104 hunter-gatherer 94 sewage 76 terrestrial 71 built environment 46 sludge 31 preterm birth 31 ancient microbiome 24 insect host 20 low temperature 19 hospital 17 medium temperature 16 agriculture 12 marine 11 skin 10 soil 8 grassland 6 anaerobic 6 cropland 4 wetland 2 lentic 2 subsurface 2 contaminated 2 very low temperature 2 paludal 2 fermented food 1 air 1 food 1