Inactivation of Bacillus subtilis by Curcumin-Mediated Photodynamic Technology through Inducing Oxidative Stress Response

Abstract

Photodynamic sterilization technology (PDT) is widely used in disease therapy, but its application in the food industry is still at the research stage because of the limitations of food-grade photosensitizers. Curcumin exhibits photosensitivity and is widely used as a food additive for its natural color. This study aimed to determine the effect of curcumin-mediated photodynamic technology (Cur-PDT) on Bacillus subtilis and to elucidate the anti-bacterial mechanism involved. First, the effects of curcumin concentration, duration of light irradiation, light intensity, and incubation time on the inactivation of B. subtilis were analyzed. It was found that Cur-PDT inactivated 100% planktonic cells with 50 μmol/L curcumin in 15 min (120 W). Then, the cell morphology, oxidation state and the expression of membrane structure- and DNA damage-related genes of B. subtilis vegetative cells were investigated under different treatment conditions. The membrane permeability of cells was enhanced and the cell membrane structure was damaged upon treatment with Cur-PDT, which were exacerbated with increases of treatment time and curcumin concentration. Meanwhile, the production of reactive oxygen species increased and the activities of the antioxidant enzymes SOD, GPX, and CAT decreased inside the cells. Furthermore, the Cur-PDT treatment significantly downregulated the mRNA of the membrane protein TasA and upregulated the DNA damage recognition protein UvrA and repair protein RecA of B. subtilis. These results suggested that curcumin-mediated PDT could effectively inactivate B. subtilis by inducing cell redox state imbalance, damaging DNA, and disrupting membrane structures.

Elimination of Human Papillomavirus and Cervical Pathological Microbiota with Photodynamic Therapy in Women from Mexico City with Cervical Intraepithelial Neoplasia I

“…This study agrees with previous works indicating the inactivation of C. albicans in vitro by PDT (50), we found that with our PDT scheme 81.8% and 72.7% of the patients were free of infection after 3 and 6 months, respectively. In the task of understanding the mechanism of action of PDT on microorganisms, studies carried out on Bacillus subtilis in vitro found that the treatment with Curcumin and PDT increased the permeability of the membrane in a dependent manner of the curcumin concentration, they also observe the production of reactive oxygen species and the decrease of antioxidant enzymes, which shows that PDT induces DNA and membrane damage (51). In addition, PDT in fungal cells induced nuclear and mitochondrial oxidative damage (43) and death by apoptosis (52).…”

Polyphenolic natural products as photosensitizers for antimicrobial photodynamic therapy: recent advances and future prospects

“…As a natural compound, curcumin has been widely investigated as a PS in aPDT. For instance, Li et al demonstrated the effective eradication of Bacillus subtilis (B. subtilis) through curcuminmediated PDT by inducing an imbalance in the cellular redox state, causing DNA damage and disrupting membrane structures (13). Wang et al demonstrated that curcumin (25 mM)-mediated aPDT could inhibit 5 log CFU/ml of Staphylococcus saprophyticus (S. saprophyticus) with the irradiation parameters (430-470 nm, 4.32 J/cm 2 10 min) in food production (34).…”

“…One notable advantage of aPDT is its noninvasive or minimally invasive nature, which enables a targeted approach primarily against the microorganisms, sparing animal tissue cells from unnecessary damage. This relatively simple and selective approach ensures effective pathogen elimination while minimizing harm to the host (13). The fundamental components of aPDT include the light, PSs, and ambient oxygen.…”