host-associated 33,704 animal host 33,701 digestive tract 33,598 intestine 32,631 mammalian host 32,538 human host 28,915 industrialized 23,578 adult 13,277 urban 4,104 infant 3,255 child 2,860 elderly 2,259 rural 2,018 non-industrialized 1,786 mouth 1,133 adolescent 835 saliva 767 full term birth 604 rumen 462 traditional agriculturalist 429 anthropogenic 272 preterm birth 241 terrestrial 199 aquatic 182 hunter-gatherer 138 wastewater 124 built environment 105 sewage 102 airways 78 urogenital tract 48 ancient microbiome 41 sludge 40 insect host 39 agriculture 36 soil 26 marine 22 hospital 22 low temperature 20 anaerobic 20 medium temperature 20 fresh water 17 grassland 16 skin 16 fermented food 15 subsurface 15 food 15 lentic 14 wetland 14 paludal 14 groundwater 13 low salinity 12 cropland 9 very low temperature 7 ancient dental calculus 4 contaminated 4 ice 3 plant host 3 stream 2 high temperature 2 tundra 2 mine 2 benthic 1 briny water 1 very high salinity 1 phyllosphere 1 waste 1 forest 1 pelagic 1 permafrost 1 sediment 1 air 1