Final answer:
Group D Strep nonenterococci are normal flora in the human mouth, aerotolerant anaerobes, and catalase-negative. They contribute to oral health but some species like S. mutans can lead to dental caries.
Step-by-step explanation:
Group D Strep nonenterococci species are a subset of streptococci that are considered normal flora, primarily inhabiting the human mouth and not categorized as enterococci which are found in the GI tract. These nonenterococci are different from the pathogenic streptococci, as they are generally nonpathogenic, aerotolerant anaerobes, and are catalase-negative. Furthermore, their growth on blood agar does not produce hemolysis typical of some Streptococcus species, such as the beta-hemolytic Group A streptococci. Instead, they either display non-hemolysis or alpha-hemolysis. These normal flora organisms are part of the resident microbiota and contribute to maintaining oral health, although some, like S. mutans, can contribute to dental caries when conditions enable their overgrowth.