host-associated 4,144 animal host 4,130 digestive tract 4,113 intestine 4,082 mammalian host 3,786 human host 3,435 industrialized 2,899 adult 1,534 aquatic 1,260 terrestrial 573 lentic 539 fresh water 519 urban 451 low salinity 447 benthic 343 marine 333 soil 283 anthropogenic 277 lacustrine 252 sediment 246 wetland 219 paludal 217 elderly 195 rural 161 non-industrialized 153 subsurface 147 wastewater 147 lotic 142 groundwater 134 spring 123 sludge 123 high salinity 111 child 88 adolescent 87 sewage 81 saline water 80 very high temperature 76 sea floor 74 hydrothermal vent 67 contaminated 62 permafrost 59 low temperature 58 hot spring 56 brackish water 52 medium salinity 52 infant 50 anaerobic 40 littoral 33 built environment 32 medium temperature 31 forest 30 alkaline 30 pelagic 28 microaerobic 26 mouth 26 very low temperature 25 stream 23 very high salinity 21 estuary 20 agriculture 20 tundra 19 fluvial 19 mine 17 salt marsh 15 plant host 14 rhizosphere 12 high temperature 12 coral reef 12 ancient microbiome 11 rumen 11 lake bed 10 ancient dental calculus 10 food 8 dairy product 8 stream bed 7 waste 7 traditional agriculturalist 6 full term birth 6 insect host 6 ice 5 saliva 5 hospital 4 acidic 4 hunter-gatherer 3 grassland 2 briny water 2 mangrove 2 phyllosphere 1