animal host 2,585 host-associated 2,585 digestive tract 2,551 mammalian host 2,528 human host 2,252 industrialized 2,076 intestine 1,935 adult 1,413 mouth 1,139 saliva 738 urban 593 child 395 aquatic 184 anthropogenic 146 wastewater 141 elderly 132 sewage 132 adolescent 110 airways 104 terrestrial 95 built environment 80 infant 47 marine 32 rural 24 urogenital tract 24 non-industrialized 23 low temperature 22 high salinity 20 medium temperature 13 sludge 11 fresh water 9 low salinity 8 preterm birth 8 soil 7 benthic 6 skin 6 insect host 5 ancient microbiome 4 lentic 4 lotic 4 very low temperature 4 traditional agriculturalist 4 sediment 4 agriculture 3 lacustrine 3 cropland 2 very high temperature 2 hydrothermal vent 2 sea floor 2 fluvial 2 groundwater 2 spring 2 stream 2 subsurface 2 ancient dental calculus 2 anaerobic 2 saline water 1 hunter-gatherer 1 hospital 1