Arginine is primarily metabolized to ornithine, ammonia, and CO2 by abundant oral bacteria.

• A. Lactobacillus casei
• B. Escherichia coli
• C. Candida albicans
• D. Ornithine, ammonia, and CO2

Answer: (D)

Arginine metabolism in dental plaque often proceeds via the arginine deiminase system, which converts arginine into ornithine with the release of ammonia and carbon dioxide. This pathway not only provides a source of energy for certain oral bacteria but also raises the pH of the biofilm by releasing ammonia, helping to counteract acidification from carbohydrate fermentation.

The correct choice is the option that lists ornithine, ammonia, and CO2 as the end products. That set of metabolites exactly matches what the arginine deiminase pathway yields in abundant oral bacteria. The other options name organisms, which may be present in the mouth, but they do not describe the metabolic end products of arginine breakdown.