TNF and periodontal disorder: Similar to Wei et al’s study, we observed there was a greater abundance of Streptococcus but this change in microbiome composition was related to a reduced expression of genes important for barrier function, particularly RANK, TNFA and AHR. In contrast, Fusobacterium, a gram-negative anaerobe and a known contributor to periodontal disease, appears to thrive under conditions with higher expression of RANK and AHR, which may relate to the parallel increase in hypoxia with inflammation [52].