Propionibacterium is a gram-positive, anaerobic, rod-shaped genus of bacteria named for their unique metabolism: They are able to synthesize propionic acid by using unusual transcarboxylase enzymes.

They are virtually ubiquitous and do not cause problems for most people, but propionibacteria have been implicated in acne and other skin conditions.

[6] Members of the genus Propionibacterium are widely used in the production of vitamin B12, tetrapyrrole compounds, and propionic acid, as well as in the probiotics and cheese industries.

[10][11] Acne vulgaris cannot be defined as an infectious disease since the bacteria is found on a vast majority of individuals without causing lesions.

[16] The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[2] and National Center for Biotechnology Information (NCBI)[17] P. freudenreichii van Niel 1928 (Approved Lists 1980) P. cyclohexanicum Kusano et al. 1997 P. acidifaciens Downes and Wade 2009 P. australiense Bernard et al. 2002 P. ruminifibrarum Vaidya et al. 2019 P. cyclohexanicum P. freudenreichii P. acidifaciens P. australiense P. ruminifibrarum