host-associated 2,670 animal host 2,670 intestine 2,670 digestive tract 2,670 mammalian host 2,612 human host 2,481 industrialized 2,074 adult 1,148 urban 307 elderly 220 child 85 infant 59 rural 57 adolescent 52 non-industrialized 37 traditional agriculturalist 8 full term birth 2 ancient microbiome 1