host-associated 13,481 animal host 13,398 digestive tract 13,174 intestine 13,162 mammalian host 12,957 human host 12,235 industrialized 8,306 infant 4,654 adult 3,443 urban 1,503 preterm birth 1,501 elderly 982 rural 786 non-industrialized 704 child 670 terrestrial 655 anthropogenic 611 built environment 480 full term birth 390 adolescent 171 aquatic 167 skin 159 traditional agriculturalist 156 insect host 109 plant host 86 soil 84 wastewater 78 sewage 63 hospital 57 hunter-gatherer 44 rhizosphere 44 fermented food 32 food 32 phyllosphere 31 agriculture 30 marine 29 lentic 21 wetland 17 paludal 16 very low temperature 15 medium temperature 15 urogenital tract 14 sediment 11 pelagic 11 benthic 11 airways 11 arid 10 low temperature 10 fresh water 10 forest 9 ancient microbiome 9 low salinity 7 sludge 7 air 6 permafrost 5 contaminated 5 medium salinity 5 littoral 5 mouth 4 grassland 4 stream 4 acidic 4 brackish water 4 plant litter 4 mine 4 saliva 3 negative control 2 high salinity 2 lacustrine 2 cropland 2 fluvial 2 alkaline 1 stream bed 1 subsurface 1 sea floor 1 rumen 1 lake bed 1 lotic 1 coral reef 1 groundwater 1 mangrove 1