Filifactor alocis enhances survival of Porphyromonas gingivalis W83 in response to H 2 O 2 -induced stress.

A dysbiotic microbial community whose members have specific/synergistic functions that are modulated by environmental conditions, can disturb homeostasis in the subgingival space leading to destructive inflammation, plays a role in the progression of periodontitis. Filifactor alocis, a gram-positive, anaerobic bacterium, is a newly recognized microbe that shows a strong correlation with periodontal disease. Our previous observations suggested F. alocis to be more resistant to oxidative stress compared to Porphyromonas gingivalis. The objective of this study is to further determine if F. alocis, because of its increased resistance to oxidative stress, can affect the survival of other 'established' periodontal pathogens under environmental stress conditions typical of the periodontal pocket. Here, we have shown that via their interaction, F. alocis protects P. gingivalis W83 under H2 O2 -induced oxidative stress conditions. Transcriptional profiling of the interaction of F. alocis and P. gingivalis in the presence of H2 O2 -induced stress revealed the modulation of several genes, including those with ABC transporter and other cellular functions. The ABC transporter operon (PG0682-PG0685) of P. gingivalis was not significant to its enhanced survival when cocultured with F. alocis under H2 O2 -induced oxidative stress. In F. alocis, one of the most highly up-regulated operons (FA0894-FA0897) is predicted to encode a putative manganese ABC transporter, which in other bacteria can play an essential role in oxidative stress protection. Collectively, the results may indicate that F. alocis could likely stabilize the microbial community in the inflammatory microenvironment of the periodontal pocket by reducing the oxidative environment. This strategy could be vital to the survival of other pathogens, such as P. gingivalis, and its ability to adapt and persist in the periodontal pocket.