host-associated 2,433 animal host 2,381 mammalian host 2,097 human host 1,943 industrialized 1,766 digestive tract 1,347 skin 955 adult 915 terrestrial 817 intestine 814 mouth 756 anthropogenic 658 elderly 620 built environment 526 aquatic 452 saliva 433 urban 241 soil 237 child 175 lentic 171 fresh water 155 low salinity 136 lacustrine 127 wastewater 117 sludge 111 marine 103 airways 97 forest 61 hospital 61 infant 60 agriculture 55 high salinity 54 plant host 53 benthic 49 wetland 49 paludal 49 sediment 49 urogenital tract 43 preterm birth 39 adolescent 39 pelagic 39 anaerobic 34 contaminated 31 very low temperature 30 rhizosphere 28 rural 27 medium salinity 22 medium temperature 22 non-industrialized 21 low temperature 21 brackish water 20 permafrost 18 grassland 18 lake bed 14 insect host 12 cropland 9 stream 9 lotic 8 very high salinity 7 subsurface 7 sewage 5 groundwater 5 traditional agriculturalist 5 hot spring 4 spring 4 fluvial 3 plant litter 3 littoral 3 arid 3 estuary 3 phyllosphere 2 tundra 2 mine 2 negative control 2 sea floor 2 saline water 2 ice 2 full term birth 2 ancient dental calculus 2 waste 2 ancient microbiome 2 acidic 1 salt marsh 1