host-associated 1,760 animal host 1,759 digestive tract 1,753 intestine 1,743 mammalian host 1,703 human host 1,546 industrialized 880 infant 746 preterm birth 340 adult 320 rural 176 non-industrialized 170 child 141 urban 117 full term birth 82 elderly 52 adolescent 35 terrestrial 28 anthropogenic 26 hunter-gatherer 15 agriculture 14 built environment 13 aquatic 12 rumen 10 traditional agriculturalist 8 sludge 6 lentic 6 wetland 5 paludal 5 ancient microbiome 4 cropland 4 anaerobic 4 medium temperature 4 soil 3 wastewater 2 sewage 2 grassland 1 sediment 1 fresh water 1 marine 1 low salinity 1 air 1 plant host 1 lake bed 1 rhizosphere 1 lacustrine 1