Which of the following BEST describes the bacteria associated with periodontitis?

Chronic periodontitis is associated with gram-negative anaerobic bacilli (rods) — the classic red complex includes Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola. Other important periodontal pathogens include Fusobacterium nucleatum, Prevotella intermedia, Aggregatibacter actinomycetemcomitans. As disease severity increases, the microbiota shifts from gram-positive aerobes (healthy sulcus) to gram-negative anaerobes (diseased pockets). This shift is fundamental to understanding periodontal disease progression.