During fasting, what carbohydrate source do bacteria use?

During fasting, what carbohydrate source do bacteria use?

• A. Dietary starch
• B. Glycosaminoglycans
• C. Host DNA
• D. Salivary glycans

Answer: (D)

The key idea is that when you’re not taking in food, oral bacteria turn to what’s already in the mouth. Saliva is rich in glycoproteins and mucins that carry many sugar chains, called salivary glycans. Bacteria in dental plaque have enzymes to break down these glycans and harvest the sugars, keeping them fed even during fasting. Dietary starch isn’t present without eating, so it isn’t a usable source at that time. Glycosaminoglycans are structural polymers found in tissues and aren’t readily available as free substrates in saliva during fasting. Host DNA isn’t a carbohydrate, so it wouldn’t serve as a food source for carbohydrate metabolism. So the readily available host-derived carbohydrate source in the fasting oral environment is salivary glycans.

The key idea is that when you’re not taking in food, oral bacteria turn to what’s already in the mouth. Saliva is rich in glycoproteins and mucins that carry many sugar chains, called salivary glycans. Bacteria in dental plaque have enzymes to break down these glycans and harvest the sugars, keeping them fed even during fasting. Dietary starch isn’t present without eating, so it isn’t a usable source at that time. Glycosaminoglycans are structural polymers found in tissues and aren’t readily available as free substrates in saliva during fasting. Host DNA isn’t a carbohydrate, so it wouldn’t serve as a food source for carbohydrate metabolism. So the readily available host-derived carbohydrate source in the fasting oral environment is salivary glycans.