Nutrition of the Mouse. IV. Comparison of Bacterial Population of Two Highly Inbred Strains. ∗

Summary and Conclusions

1. Studies were made to determine whether there is a difference in the weight and bacterial population of the cecal contents of mice of the C₅₇ and A strains, which were the same age and received the same diet.

2. The C₅₇ animals fed a synthetic diet (No. 101) had a significantly greater amount of cecal contents and bacterial count per cecum than the A strain mice of the same age and fed the same diet. Although most of the bacterial flora appeared to be the same in the 2 strains, a Gram-negative, anaerobic rod did occur more frequently in the C₅₇ mice than in the A strain.

3. There was no significant difference between the black and white mice of the same age fed the stock ration with respect to weight of cecal contents or bacterial count per cecum. The young black mice may have had a more diverse flora than the white mice of the same age.

4. It was postulated that this greater weight of cecal contents with its higher bacterial population in the C₅₇ mice might help to explain the lower B vitamin requirements of this strain when comparing it with animals of the A strain, both fed the same synthetic diet.