host-associated 18,835 animal host 18,835 digestive tract 18,823 intestine 18,487 mammalian host 18,042 human host 15,033 industrialized 12,523 adult 6,738 urban 1,918 elderly 1,325 child 1,266 rural 992 non-industrialized 858 infant 646 rumen 410 adolescent 385 traditional agriculturalist 164 anthropogenic 99 hunter-gatherer 83 terrestrial 78 full term birth 56 aquatic 42 preterm birth 40 built environment 38 wastewater 28 agriculture 25 sludge 25 ancient microbiome 22 sewage 19 anaerobic 17 grassland 15 insect host 14 hospital 12 medium temperature 11 marine 9 fermented food 6 food 6 cropland 5 soil 5 skin 4 wetland 3 lentic 3 low temperature 3 paludal 3 subsurface 3 fresh water 2 groundwater 2 tundra 2 contaminated 1 low salinity 1 mouth 1 air 1 high temperature 1