animal host 3,470 host-associated 3,470 digestive tract 3,466 mammalian host 3,330 intestine 3,167 human host 2,484 industrialized 1,922 adult 765 non-industrialized 340 child 307 rural 304 rumen 293 elderly 251 urban 149 anthropogenic 116 terrestrial 110 aquatic 87 infant 61 ancient microbiome 58 ancient dental calculus 55 mouth 55 adolescent 51 sludge 43 lentic 38 wetland 35 paludal 35 anaerobic 35 wastewater 35 hunter-gatherer 29 soil 28 fermented food 23 food 23 traditional agriculturalist 20 fresh water 19 sewage 16 medium temperature 14 low salinity 14 groundwater 11 agriculture 11 grassland 11 subsurface 11 low temperature 10 permafrost 10 built environment 9 mine 7 contaminated 5 cropland 4 benthic 3 sediment 3 tundra 3 lacustrine 3 lake bed 2 full term birth 2 very low temperature 2 alkaline 1