animal host 3,273 host-associated 3,273 digestive tract 3,272 intestine 3,271 mammalian host 3,196 human host 3,010 industrialized 2,539 adult 1,405 urban 391 elderly 257 child 104 infant 74 rural 61 adolescent 59 non-industrialized 40 aquatic 17 low salinity 12 stream 12 fluvial 12 fresh water 12 lotic 12 traditional agriculturalist 8 marine 5 benthic 4 sediment 4 full term birth 2 insect host 2 preterm birth 1 mouth 1 ancient microbiome 1