digestive tract 3,265 host-associated 3,265 animal host 3,265 mammalian host 3,168 intestine 3,036 human host 2,472 industrialized 1,917 adult 760 non-industrialized 336 rural 300 child 252 elderly 250 rumen 207 urban 149 ancient microbiome 58 infant 56 ancient dental calculus 55 mouth 55 adolescent 51 hunter-gatherer 29 traditional agriculturalist 20 aquatic 13 wastewater 13 anthropogenic 13 sewage 12 low temperature 4 medium temperature 4 full term birth 2 terrestrial 1 paludal 1 very low temperature 1 lentic 1 wetland 1