Table 4

Total number of prokaryotes in some representative animals

AnimalOrganCells/ml or cells/gOrgan contents*No. of animalsNo. of cells, × 1023Refs.
HumanColon3.2  ×  1011220 g5.6  ×  1093.945, 46
CattleRumen2.1  ×  1010106 liter1.3  ×  10929.047, 48
Sheep and goatsRumen4.4  ×  1010 12 liter1.7  ×  1099.047, 48
PigsColon5.4  ×  1010  9 liter8.8  ×  1084.349, 50
Cecum2.8  ×  1010  1 liter8.8  ×  1080.349, 50
Domestic birds§Cecum9.5  ×  1010  2 g1.3  ×  10100.02451, 52
TermitesHindgut2.7  ×  1062.4  ×  10176.5 53
  • * Organ contents in volume or grams of wet weight. For comparison, the volume of the human colon is 0.5 liter. For domestic birds, weight wet was calculated from a volume of 2 ml assuming that 1 ml - 1 g wet weight. 

  • Values from the FAO Production Yearbook (54), except for the termites value which was from ref. 55

  • The direct count was assumed to be 2.7 × viable count (56). 

  • § Includes chickens, ducks, and turkeys. 

  • Per termite.