Distinguish between acidogenic and aciduric bacteria with examples from the oral cavity.

• A. Acidogenic bacteria efficiently produce acid from carbohydrates (e.g., Streptococcus mutans); aciduric bacteria tolerate and thrive at low pH (e.g., Lactobacillus spp.).
• B. Acidogenic bacteria produce ammonia to neutralize acid; aciduric bacteria rely on oxygen.
• C. Acidogenic bacteria thrive at high pH; aciduric bacteria require neutral pH.
• D. Acidogenic bacteria are the same as aciduric bacteria.

Answer: (A)

Acid-related traits in oral bacteria help explain their roles in caries: some generate acid from carbohydrate metabolism, while others are tolerant of acidic environments. The statement correctly identifies Streptococcus mutans as an acidogenic organism that efficiently ferments carbohydrates to produce acid, which lowers the pH and initiates enamel demineralization. It also correctly notes Lactobacillus species as aciduric, meaning they can survive and even flourish in the acidic conditions that follow, contributing to lesion progression. This distinction matters because acid producers drive the initial drop in pH, while acid-tolerant organisms persist and continue to damage tooth structure as the environment becomes more acidic. The other ideas mix in unrelated or incorrect concepts: producing ammonia to neutralize acid is a different microbial strategy (alkalinogenic rather than a defining feature of aciduricity); relying on oxygen is not what aciduricity refers to; thriving at high pH or requiring neutral pH contradicts the idea of acid tolerance; and saying the two are the same ignores the important difference between acid production and acid tolerance.