A novel antibacterial mechanism of atmospheric cold plasma against Staphylococcus aureus through degradation of cellular staphyloxanthin

Atmospheric cold plasma (ACP) is an emerging non-thermal food sterilization technology. This study investigated the effects of ACP on the antioxidant membrane-bound triterpenoid carotenoid pigment (staphyloxanthin, STX) in S. aureus. Results showed that the survival rate of S. aureus in water (1.3 × 10⁷ CFU/mL) after ACP treatment for 5, 10, 15, 20 min significantly decreased to 55.0%, 18.5%, 9.7% and 4.1%, accompanied by a decrease of STX content from 448.8 to 276.7, 80.3, 45.1 and 19.7 μg/mL, respectively. Particularly, 20-min ACP-treated S. aureus became more susceptible (4.79 times) to hydrogen peroxide (0.1 M) attack most probably due to the decrease of STX. ACP also caused a decrease in the cell membrane potential (MP), accumulation of intracellular reactive oxygen species (ROS), and cell necrosis. Pearson correlation analysis indicated that the survival rate, MP, intracellular ROS, and cell necrosis were all highly correlated to STX content, indicating that STX contributed to ACP-induced physiological alterations in S. aureus. These results demonstrated that STX was an important attack target during ACP inactivation of S. aureus. Industrial relevance: This study proposes a novel antibacterial mechanism of ACP against S. aureus from the perspective of STX, which would accelerate the development of ACP in food sterilization. Noting that pigmentation is a hallmark of multiple foodborne pathogenic microbes, this work shows the exciting potential of inactivating foodborne pathogens through destroying their intrinsic pigments.