Describe how dental plaques develop, including the different types of bacteria that colonize (and when) and the different types of metabolism they exhibit that contributes to gum and tooth decay.

Question

What will be an ideal response?

Answer 1

The oral microbiome is a diverse community (~ 500 taxa) that contains both aerobic and anaerobic members. Bacteria often develop biofilms called plaques in the gingival crevice. If plaque growth in the gingival crevice is not inhibited, the microbial population can shift from a mix of Gram positive and Gram negative species to one being dominated by Gram negatives. After that, spirochete bacteria begin to appear. These new populations releases proteases that destroy gum tissue. The resulting inflammatory response gives rise to bleeding gums and eventually receding gums and tooth loss.
Another set of bacteria that are common in the human mouth are lactic acid bacteria (Gram positives). These bacteria are what are referred to as aerotolerant anaerobes, meaning they don't use oxygen but can grow in its presence. These guys are important to us because of their metabolism. They breakdown sugars like glucose into pyruvate, then reduce pyruvate to lactate through fermentation. The lactate that is leftover is no good for the bacteria, so they excrete it into their surroundings. These bacteria do not generate much ATP, so they make up for this by processing more glucose molecules per unit time than if they used pyruvate in aerobic cellular respiration. The lactic acid bacteria grow so rapidly and produce so much lactic acid, which inhibits the growth of other bacteria, that they soon come to dominant the enrichment culture. The problem for us with lactic acid bacteria involves the amount of sugar in our diet. When our sugar intake is low, these bacteria do not produce enough lactic acid in a short enough time period to damage the enamel on our teeth. A high sugar diet, however, allows them to produce high concentrations of lactic acid, which undermines the integrity of the tooth enamel and results in a cavity.