host-associated 31,268 animal host 31,266 digestive tract 31,230 intestine 30,826 mammalian host 30,054 human host 25,999 industrialized 21,154 adult 12,466 urban 3,616 child 2,571 elderly 2,240 rural 2,043 non-industrialized 1,835 infant 1,725 adolescent 762 rumen 488 traditional agriculturalist 421 full term birth 398 anthropogenic 317 aquatic 201 terrestrial 177 wastewater 164 hunter-gatherer 149 sewage 124 built environment 97 preterm birth 96 sludge 73 ancient microbiome 34 agriculture 33 medium temperature 29 insect host 27 food 26 fermented food 26 anaerobic 26 low temperature 22 hospital 22 soil 17 marine 16 grassland 16 skin 12 fresh water 11 subsurface 11 lentic 10 groundwater 9 paludal 8 wetland 8 cropland 6 very low temperature 5 low salinity 5 contaminated 4 plant host 2 alkaline 2 permafrost 2 saline water 2 lacustrine 2 high temperature 2 waste 2 high salinity 2 tundra 2 air 1 mouth 1