Which bacteria colonize subgingivally in plaque?

• A. Streptococci
• B. Spirochetes
• C. Staphylococci
• D. Lactobacilli

Answer: (B)

Subgingival plaque sits in an anaerobic, inflamed niche inside periodontal pockets, selecting for bacteria adapted to low oxygen and tissue breakdown. Spirochetes are slender, spiral-shaped anaerobes that thrive in this environment and are well known residents of subgingival biofilms. Their motility helps them navigate the sulcular space, and they contribute to periodontal tissue destruction through enzymes and toxins released in the pocket. In contrast, Streptococci are classic early colonizers of supragingival enamel, lactobacilli are more associated with caries progression on root surfaces, and Staphylococci are not typical dental plaque residents. So the subgingival plaque community is characterized by spirochetes among other anaerobes, reflecting the distinct ecological niche beneath the gum line.