animal host 1,686 host-associated 1,686 intestine 1,685 digestive tract 1,685 mammalian host 1,678 human host 1,560 industrialized 1,426 adult 800 urban 291 elderly 122 child 108 adolescent 40 infant 37 rural 15 non-industrialized 10 soil 4 terrestrial 4 full term birth 3 hunter-gatherer 2 ancient microbiome 2 skin 1 traditional agriculturalist 1