host-associated 39,877 animal host 39,868 digestive tract 39,616 mammalian host 38,408 intestine 38,285 human host 33,551 industrialized 26,830 adult 15,469 urban 4,823 infant 4,558 child 3,410 elderly 2,676 rural 2,272 non-industrialized 2,108 mouth 1,594 saliva 1,111 adolescent 1,030 preterm birth 834 full term birth 710 anthropogenic 624 rumen 589 traditional agriculturalist 508 terrestrial 477 aquatic 464 wastewater 254 built environment 238 hunter-gatherer 186 sewage 172 sludge 151 ancient microbiome 112 airways 108 skin 101 urogenital tract 90 soil 81 lentic 81 agriculture 76 ancient dental calculus 73 fresh water 67 anaerobic 52 low salinity 50 marine 48 insect host 44 subsurface 41 wetland 39 paludal 37 medium temperature 36 benthic 34 hospital 32 sediment 31 groundwater 30 food 30 contaminated 28 fermented food 26 high salinity 25 low temperature 23 lacustrine 20 alkaline 18 grassland 17 very low temperature 16 tundra 16 mine 15 lotic 14 spring 13 hot spring 12 cropland 11 very high salinity 10 plant host 9 permafrost 8 saline water 7 ice 7 waste 6 littoral 5 forest 5 dairy product 4 rhizosphere 4 high temperature 3 arid 3 stream 3 air 2 coral reef 2 mangrove 2 brackish water 2 medium salinity 2 hydrothermal vent 1 fluvial 1 phyllosphere 1 briny water 1 lake bed 1 pelagic 1 negative control 1 very high temperature 1 sea floor 1