animal host 5,265 host-associated 5,265 digestive tract 5,263 intestine 5,156 mammalian host 4,981 human host 3,527 industrialized 2,916 adult 1,704 child 465 urban 417 elderly 308 rural 237 non-industrialized 199 infant 155 rumen 125 adolescent 77 traditional agriculturalist 54 hunter-gatherer 33 anthropogenic 15 agriculture 13 aquatic 7 marine 6 built environment 5 ancient microbiome 5 terrestrial 5 hospital 2 full term birth 2 wastewater 1 sewage 1 skin 1 soil 1