Reemerging Importance of Methanogenic Archaea in the Landscape of Periodontal Disease

Periodontal disease is the most common chronic inflammatory condition with a polymicrobial origin, particularly among the elderly. Numerous risk factors can independently or synergistically contribute to immune suppression and inflammation in the periodontium. This leads to microbial dysbiosis in the periodontal pockets and the supra gingival biofilm, resulting in the elevation of patho bionts or opportunistic pathogens that are considered potential contributors to periodontal disease. The progression from gingivitis to chronic periodontitis typically follows an ecological succession, starting with the facultative anaerobes of the yellow complex and advancing to the strict anaerobes of the red complex of periodontal pathogens. Additionally, there has been an observed increase in sulfate-reducing bacteria (SRB) within the oral cavities, which are part of the human oral microbiome. SRB is a diverse group of naturally occurring microorganisms known for their capability of dissimilatory sulfate reduction to hydrogen sulfide (H2S). Methanogenic archaea are a minority within the SRB group, known for their hydrogenotrophic metabolism and cooperative growth alongside other species in the periodontal pockets. However, these methanogenic archaea are not typically recognized as contributors to the development of periodontal disease. Investigating the role of methanogenic archaea in the context of periodontal disease enhances our understanding of the dynamics within the supragingival biofilm associated with chronic periodontitis.