Abstract: The effect of ε-polylysine (ε-PL) on the cell structure and energy metabolism of Saprophytic staphylococcus was investigated in this paper. The minimal inhibitory concentration (MIC) was determined by broth dilution method, and the impact of ε-PL on cell morphology was evaluated according to the growth curve, the activities of alkaline phosphatase (AKP) and adenosine triphosphatase (ATPase), electrical conductivity, ultraviolet (UV) absorbance and scanning electron microscope (SEM) observation. The impact of ε-PL on cell metabolism was investigated by cell protective enzyme activities such as peroxidase (POD) and catalase (CAT), tricarboxylic acid metabolic enzyme activities such as succinodehydrogenase (SDH) and malic dehydrogenase (MDH), and cell metabolic activity. The results showed that the MIC was determined to be 1.0 mg/mL. ε-PL was able to inhibit bacterial growth, destroy the integrity of the cell wall and increase the permeability of the cell membrane. SEM revealed that the bacterial cells were distorted and deformed with rough surfaces after being treated with ε-PL at MIC, while after being treated with ε-PL at 2 MIC, some cells were adhered to each other and obvious morphological damage was observed. The activities of ATPase, POD, CAT, SDH and MDH were significantly decreased by treatment with ε-PL in a concentration-dependent manner (P < 0.05), indicating ε-PL to be effective in inhibiting the energy metabolism of Saprophytic staphylococcus. Moreover, ε-PL could damage the morphology of bacterial cells, and alter the cell membrane permeability, thereby affecting bacterial growth and metabolism and finally causing bacterial death.

Key words: ε-polylysine; Saprophytic staphylococcus; cell structure; energy metabolism