Streptococcus mutans is a type of bacteria commonly found in the human mouth. It plays a significant role in the development of dental caries, or cavities, by converting sugars from food into acids. These acids can erode tooth enamel, leading to tooth decay. This bacterium is part of the normal oral microbiota but can become harmful when sugar intake is high. Streptococcus mutans can form biofilms, known as dental plaque, which adhere to teeth and contribute to further dental issues if not properly managed through good oral hygiene practices.