Higher-order metabolic interactions among oral commensals gate pathobiont expansion through succinate-driven pH modulation

Succinate-driven acidification in a six-species synthetic oral community suppresses Porphyromonas gingivalis growth, with antagonism modulated by oxygen and reversed at high Veillonella parvula density.

• Why it matters: Microbiome studies link inflammation to shifts, but the specific ecological interactions that limit or enable pathobiont expansion in oral disease are still unclear.
• What they did: Using factorial interaction screening in a six-species oral community, the study tested how Actinomyces oris and V. parvula affect P. gingivalis, then analyzed subgingival microbiomes from 1,355 adults (555 with detectable P. gingivalis).
• The result: A. oris reduced P. gingivalis growth via extracellular acidification enhanced anaerobically, with succinate from the sdh2 pathway as the principal driver; in vivo, P. gingivalis abundance was negatively associated with Actinomyces after adjusting for periodontitis severity, and this association weakened at high V. parvula.

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