host-associated 2,013 animal host 2,012 digestive tract 2,012 intestine 2,001 mammalian host 1,937 human host 1,724 industrialized 1,441 adult 705 urban 176 rural 123 non-industrialized 117 elderly 98 adolescent 48 child 48 infant 21 aquatic 12 anthropogenic 11 wastewater 10 rumen 10 sewage 8 mouth 5 traditional agriculturalist 5 low temperature 4 saliva 4 hunter-gatherer 3 terrestrial 3 sludge 2 ancient microbiome 1 plant host 1 anaerobic 1 waste 1 medium temperature 1 built environment 1