Which of the following statements about the microbiology of the colon is/are true?

C. Nearly one third of the dry weight of feces is bacteria

D. Common bacteria in the colon are Bacteroides, Bifidobacterium, and Enterobacterium species.

E. The colonic microflora is relatively stable.

DISCUSSION: The number of bacteria in the colon approaches 10 12 colony-forming units per ml., which is as many as the space in the colonic lumen allows and many more than in the stomach. The colonic microflora is relatively stable with a predominance of anaerobic bacteria. Typical species are Bacteroides, Bifidobacterium, and Enterobacterium. Depending on the fiber content of the diet, bacteria make up a significant proportion of the dry weight of feces. In the western world this can be as much as one third of the dry weight of feces.