Bacillus subtilisand Escherichia coliwere grown on 14C-labelled glucose and used for the preparation of labelled whole cells, cell walls, cell contents and peptidoglycan.
2. The radioactive samples were injected into the abomasum of sheep and the 14C appearing in expired air, plasma glucose, urine and faeces was determined. Whole cells were also injected into the rumen and the incorporation of 14C into volatile fatty acids was measured.
3. All the bacterial preparations, including cell walls, were extensively digested and absorbed, Less than 15% of the radioactivity was recovered in the faeces.
4. Up to 20% of the radioactivity injected was recovered in expired carbon dioxide with only 2.4–8.1% passing through the glucose pool.
5. It has been calculated that under the conditions of the experiment 18.5 % of the total glucose entering the body pool of glucose in 24 h was derived from bacterial carbon.