host-associated 3,973 animal host 3,973 digestive tract 3,968 mammalian host 3,802 intestine 3,333 human host 2,404 industrialized 1,872 adult 1,181 mouth 978 saliva 711 child 454 non-industrialized 326 rural 276 urban 247 elderly 203 rumen 172 adolescent 138 anthropogenic 81 ancient microbiome 70 ancient dental calculus 66 terrestrial 59 aquatic 59 infant 51 airways 45 sludge 42 wastewater 34 anaerobic 27 agriculture 24 hunter-gatherer 24 traditional agriculturalist 17 sewage 16 fresh water 9 built environment 9 lentic 8 subsurface 7 marine 7 groundwater 6 cropland 6 hospital 6 medium temperature 6 contaminated 5 low salinity 5 insect host 4 soil 4 high salinity 3 waste 3 lacustrine 3 low temperature 2 mine 2 paludal 2 high temperature 2 skin 2 grassland 2 urogenital tract 2 wetland 2 sediment 1 full term birth 1 benthic 1