Ruminococcus gnavus is a mucin-degrading bacteria belonging to Clostridia cluster XIVa,52 and has ability to produce acetate from degradation products of starch released by other bacteria.58 Recent study reported that oral administration of Ruminococcus gnavus to atopic dermatitis model mice ameliorated dermatitis symptoms along with increase of regulatory T cell in skin and mesenteric lymph node and butyrate concentration in cecum,59 suggesting anti-inflammatory effects via modulating SCFA production in the intestine. The gene discussed is MUC5AC; the disease is dermatitis.