host-associated 17,373 animal host 17,283 digestive tract 16,999 mammalian host 16,630 intestine 15,916 human host 15,113 industrialized 10,173 adult 5,007 infant 4,920 urban 1,958 preterm birth 1,568 child 1,383 rural 1,319 mouth 1,303 elderly 1,196 non-industrialized 1,172 aquatic 1,008 terrestrial 785 saliva 732 anthropogenic 730 marine 691 built environment 534 full term birth 408 adolescent 313 traditional agriculturalist 282 rumen 277 high salinity 270 pelagic 245 skin 178 wastewater 130 hunter-gatherer 120 insect host 109 soil 93 plant host 92 airways 89 fresh water 85 sewage 84 lentic 65 hospital 65 benthic 56 very low temperature 56 agriculture 54 medium salinity 51 low temperature 50 low salinity 49 brackish water 47 rhizosphere 45 subsurface 42 groundwater 37 fermented food 33 food 33 littoral 32 sediment 32 phyllosphere 31 wetland 27 medium temperature 27 saline water 27 paludal 25 ancient microbiome 25 lotic 24 stream 17 estuary 16 urogenital tract 15 sludge 15 mine 15 alkaline 14 contaminated 13 fluvial 13 spring 12 microaerobic 12 sea floor 11 lacustrine 11 hydrothermal vent 10 arid 10 forest 10 very high temperature 10 air 8 cropland 7 very high salinity 7 ancient dental calculus 6 briny water 6 permafrost 5 ice 5 grassland 4 acidic 4 plant litter 4 negative control 3 anaerobic 3 hot spring 2 waste 2 mangrove 2 stream bed 1 lake bed 1 coral reef 1