host-associated 4,037 animal host 4,035 digestive tract 4,030 intestine 4,019 mammalian host 3,760 human host 3,414 industrialized 2,891 adult 1,526 urban 444 elderly 195 rural 158 non-industrialized 143 aquatic 98 child 88 adolescent 87 terrestrial 53 infant 50 fresh water 50 anthropogenic 47 low salinity 37 lentic 26 subsurface 25 groundwater 23 wastewater 23 lacustrine 21 sewage 18 contaminated 17 sludge 15 marine 11 benthic 11 rumen 11 anaerobic 8 mine 7 sediment 7 traditional agriculturalist 6 full term birth 6 mouth 5 insect host 5 saliva 4 coral reef 4 high salinity 4 low temperature 4 wetland 3 paludal 3 hunter-gatherer 3 soil 3 built environment 3 waste 3 medium temperature 3 very high salinity 2 plant host 2 hospital 2 very low temperature 2 stream 2 phyllosphere 1 medium salinity 1 lotic 1 lake bed 1 littoral 1 fluvial 1 agriculture 1 brackish water 1 ancient microbiome 1