Impacts of the gut microbiota on arginine synthesis

The presence of the amino acid arginine–crucial for tissue deposition and protein synthesis–impacts fetal development. Lower maternal arginine availability is associated with lower birth weight. Certain microbial species are associated with specific geo-localities and diets, and some bacteria synthesize arginine. Thus, there may be diverse gut microbiota populations in pregnant women from different regions that influence arginine synthesis. In this study, we tested bacteria geographically representative of regional diets and capable of arginine synthesis. We hypothesized that arginine flux in the presence of the Bacillus megaterium would be significantly higher than in the presence of Lactobacillus acidophilus, Escherichia coli, and Clostridium sporogenes. We inoculated control plates and 4 sets of plates treated with one bacterial species (corresponding to four regional diets) with a 20% citrulline solution–an arginine precursor compound–and incubated. Their pH was evaluated during the 1-week incubation period to determine the arginine synthesis rate. The changes in the pH of C. sporogenes plates and the B. megaterium plates were significantly different from the other groups (p<0.0001). Their higher pH suggests greater synthesis of arginine. Abundances of B. megaterium and C. sporogenes are associated with Western and Mediterranean diets, respectively. This suggests that both diets offer means of gastrointestinal microbiota modulation to an environment conducive to arginine synthesis.