Porphyrin metabolisms in human skin commensal Propionibacterium acnes bacteria: potential application to monitor human radiation risk

Abstract

Propionibacterium acnes (P. acnes), a Gram-positive anaerobic bacterium, is a commensal organism in human skin. Like human cells, the bacteria produce porphyrins, which exhibit fluorescence properties and make bacteria visible with a Wood's lamp. In this review, we compare the porphyrin biosynthesis in humans and P. acnes. Also, since P. acnes living on the surface of skin receive the same radiation exposure as humans, we envision that the changes in porphyrin profiles (the absorption spectra and/or metabolism) of P. acnes by radiation may mirror the response of human cells to radiation. The porphyrin profiles of P. acnes may be a more accurate reflection of radiation risk to the patient than other biodosimeters/biomarkers such as gene up-/down-regulation, which may be non-specific due to patient related factors such as autoimmune diseases. Lastly, we discuss the challenges and possible solutions for using the P. acnes response to predict the radiation risk.

Conflict of interest statement

CONFLICT OF INTEREST

The author(s) confirm that this article content has no conflicts of interest.

Figures

Fig. (1)

Porphyrin biosynthesis pathways in humans and P. acnes. In humans, ALA is synthesized through C4 pathway (a black arrow), which is the condensation of glycine and succinyl CoA catalyzed by ALA synthase. P. acnes can go through the C5 pathway (a blue arrow) to convert glutamate to ALA. In humans, the majority end product in the biosynthesis pathway is heme. However, in P. acnes, the end product can be protoprophyrin IX (a blue arrow) or coproporphyrin III. (The color version of the figure is available in the electronic copy of the article).

Fig. (2)

Imaging auto-fluorescent P. acnes in human facial skin. A Wood’s lamp (SkinMate, Tulsa, OK) with a UV light source was used to illustrate the auto-fluorescent P. acnes (red fluorescence, arrows) in human facial skin [60].

Fig. (3)

An absorption spectrum of porphyrin. Porphyrins possess an intense Soret band at approximately 400 nm and moderate Q bands between 450 and 700 nm.