||Human Homo sapiens
||Sender R, Fuchs S, Milo R. Revised Estimates for the Number of Human and Bacteria Cells in the Body. PLoS Biol. 2016 Aug 19 14(8):e1002533. doi: 10.1371/journal.pbio.1002533. Supporting Information S1 Appendix p.4 top paragraphPubMed ID27541692
|| Stephen AM, Cummings JH. The microbial contribution to human faecal mass. J Med Microbiol. 1980 Feb13(1):45-56.PubMed ID7359576
||Supporting Information S1 Appendix p.4 top paragraph: "2. Mean bacterium mass in the colon-What fraction of colonic content is occupied by bacterial mass? What is the mean mass of a bacterium in the colon? The measurements of bacterial concentrations in the colon (table 2 BNID 112983), can be used to infer answers to those questions, provided two additional values: (1) the fraction of dried fecal mass that is dry bacteria and (2) the total water content in a bacterium. Overall dry mass fraction contributed by bacteria was directly measured to be 55% of fecal dry mass [primary source]. The dry mass percentage of cell mass varies for different types of bacteria [S1 Appendix refs 5,6] but can be assumed to be roughly equal to that of stool (29%), and thus the fraction of bacterial dry mass in dry feces is a good approximation to the fraction of bacterial mass in stool. Using the measured value of 4·10^11 bacteria per gram dry stool [primary source], [investigators] evaluate the average mass of bacteria in the Stephen and Cummings samples to be 4.6·10^-12 g (SEM 35%, CV 47%). Interestingly, this value for the average bacterial cell mass is several times higher than is usually taken for a model bacterium such as E. coli [BNID 101789 S1 Appendix refs 7,8]."
||Article p.4 bottom paragraph: "Given the dominance of bacteria in the colon over all other microbiota populations in the body, [investigators] conclude that there is about 0.2 kg of bacteria in the body overall. Given the water content of bacteria, the total dry weight of bacteria in the body is about 50–100g. This value is consistent with a parallel alternative estimate for the total mass of bacteria that multiplies the average mass of a gut bacterium of about 5 pg (wet weight, corresponding to a dry weight of 1–2 pg, see S1 Appendix (Measurement Method section above)) with the updated total number of bacteria. [They] note that this empirically observed average gut bacterium is several times bigger than the conveniently chosen “standard” 1 μm^3 volume and 1 pg wet mass bacterium often referred to in textbooks."