Temporin L peptide eradicates *Bacillus cereus* within 1 hour by disrupting membranes and metabolism

Bacillus cereus is a significant foodborne pathogen responsible for various illnesses, posing a constant challenge to food safety and public health. Current antimicrobial strategies often involve chemical preservatives or antibiotics, which can lead to resistance development or consumer concerns regarding residues. Antimicrobial peptides (AMPs) like Temporin L offer a promising alternative due to their broad-spectrum activity and distinct mechanisms of action, often targeting bacterial membranes, which reduces the likelihood of resistance. This study investigates Temporin L's efficacy and specific mechanisms against B. cereus to explore its potential as a natural food preservative.

Researchers evaluated the antimicrobial activity of Temporin L against Bacillus cereus using quantitative assays to determine its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Time-kill kinetics were assessed over 24 hours at various concentrations. The peptide's stability was tested under challenging conditions including ultraviolet (UV) light, high temperatures (up to 100 °C), and in the presence of various metal ions. Membrane integrity was analyzed via PI fluorescence and measurement of intracellular biomolecule leakage. Metabolic impact was determined by measuring NaK-ATPase, SDH, LDH activities, and intracellular ATP levels. Oxidative stress markers like ROS levels, antioxidant capacity, lipid peroxidation, and SOD activity were also quantified.

Temporin L demonstrated potent antimicrobial activity against B. cereus, with an MIC of 8 µM and an MBC of 16 µM. Complete bacterial eradication was achieved within 1 hour at 2 MIC, while complete inhibition was sustained for 24 hours at both MIC and 2 MIC. The peptide exhibited remarkable stability, retaining over 90% antibacterial activity under UV light and at temperatures up to 100 °C, with only a slight reduction to 82.11% in the presence of Fe ions. Membrane integrity assays revealed a concentration-dependent increase in PI fluorescence by 1.9-2.4 fold and significant leakage of intracellular biomolecules. Metabolic disruption was evident, with SDH and LDH activities dropping from approximately 39 U/mg protein and 43 U/mg protein respectively, to about 10 U/mg protein after 1 hour at 2 MIC. Intracellular ATP levels were also significantly reduced. > Oxidative stress markers confirmed a multifaceted damage mechanism, showing elevated ROS, decreased antioxidant capacity, increased lipid peroxidation, and reduced SOD activity.