propionibacterium acidifaciens propionibacterium acidifaciens propionibacterium acidifaciens is a gram-positive, anaerobic and pleomorphic bacterium from the genus of propionibacterium which has been isolated from a human oral cavity in london in england. propionibacterium acidifaciens scientific classification domain: bacteria phylum: actinomycetota class: actinomycetia order: propionibacteriales family: propionibacteriaceae genus: propionibacterium species: p. acidifaciens binomial name propionibacterium acidifaciensdownes and wade 2009 type strain c3m_31, ccug 57100, dsm 21887, jcm 16571