Many bacteria are named according to the shape of their cells. Which one of the following options is a round-shaped microorganism that is associated with dental caries?

Streptococcus mutans is a round-shaped bacterium, specifically classified as a coccus, that plays a significant role in the development of dental caries, or tooth decay. This microorganism is part of the normal flora of the mouth and has a high affinity for adhering to tooth surfaces, particularly in the presence of sugars. It metabolizes these sugars to produce acids, which can demineralize tooth enamel, leading to cavities.

The spherical shape of Streptococcus mutans facilitates its ability to form colonies, contributing to plaque formation on teeth, which is a critical factor in the carious process. Its capacity to thrive in acidic environments further enhances its role in dental caries, as it can outcompete other microorganisms in the mouth that may not tolerate such conditions.

In contrast, while other options like Actinomyces and Lactobacilli can also relate to dental health, they do not have the same primary association with initiating and promoting dental caries as Streptococcus mutans does. Staphylococcus aureus, while a significant pathogen in other contexts, is not typically associated with dental caries as it resides primarily in other body systems. Therefore, identifying Streptococcus mutans as the correct answer highlights its crucial role