host-associated 16,137 animal host 16,086 digestive tract 15,064 mammalian host 14,821 intestine 13,768 human host 12,727 industrialized 8,906 infant 4,458 adult 3,983 mouth 1,801 urban 1,439 elderly 1,364 preterm birth 1,211 child 1,152 saliva 1,126 anthropogenic 1,122 terrestrial 968 built environment 734 rural 637 skin 631 non-industrialized 569 aquatic 417 full term birth 403 wastewater 302 urogenital tract 277 sewage 274 adolescent 250 airways 213 soil 122 insect host 107 food 99 fermented food 99 traditional agriculturalist 87 hospital 81 agriculture 80 plant host 70 sludge 56 rhizosphere 41 marine 32 hunter-gatherer 31 rumen 27 anaerobic 26 fresh water 26 medium temperature 26 ancient microbiome 24 low temperature 24 low salinity 24 very low temperature 22 benthic 22 lentic 21 phyllosphere 20 sediment 17 dairy product 15 grassland 13 stream 11 arid 11 cropland 11 lotic 9 wetland 9 very high salinity 9 pelagic 9 mine 8 paludal 8 contaminated 8 ancient dental calculus 8 hot spring 6 forest 6 ice 6 spring 6 acidic 5 high salinity 4 coral reef 4 littoral 3 lacustrine 3 fluvial 3 subsurface 3 high temperature 2 air 2 waste 2 negative control 2 groundwater 2 medium salinity 1 mangrove 1 very high temperature 1 alkaline 1 estuary 1 saline water 1 lake bed 1 briny water 1 brackish water 1