Mingming Guo

The growing emergence of multidrug-resistant bacterial pathogens drives the need for new antibacterial agents. Punicalagin exhibits efficacy against methicillin-resistant Staphylococcus aureus (MRSA), but its specific antibacterial mechanisms remain unclear. This study unveiled the specific antibacterial mechanism of punicalagin against MRSA via phenotypic and transcriptomic analyses. Punicalagin was found to induce severe cell wall damage and membrane disruption. Competitive binding assays identified lipoteichoic acid (LTA) as a potential target, and transcriptomic analysis further revealed that punicalagin downregulated key genes involved in cell wall synthesis (murA, murE) and LTA biosynthesis (dltA-D), consistent with the disruption of the cell wall. Additionally, punicalagin disrupted membrane homeostasis by inhibiting fatty acid synthesis (fabD, fabZ) and amino acid metabolism (dapA, dapB), leading to increased membrane permeability, which aligned with the phenotypic manifestations of membrane damage. Collectively, this work links phenotypic changes to specific gene expression patterns, unveiling that punicalagin inactivates MRSA via the multi-pathway regulation of the cell wall (LTA) and membrane function—providing insights for combating antibiotic-resistant pathogens in food safety and clinical settings.

Foodborne illness outbreaks from fresh produce underscore the urgent demand for sanitizing strategies that ensure safety while minimizing harmful by-products from high-dose chemical disinfectants such as sodium hypochlorite (NaOCl). Low-concentration combinations of organic acids and washing sanitizers were systematically evaluated to identify synergistic antibacterial effects, and citric acid (CA) was found to markedly potentiate the activity of NaOCl against Salmonella Typhimurium through a sequential assault on the cell envelope. A low-dose combination of sub-inhibitory concentrations (1/2 MIC of CA and 1/4 MIC of NaOCl) exhibited robust synergy, achieving a >6 log CFU/cm² reduction in the pathogen on a cherry tomato model within 3 min. Moreover, this synergistic entry leads to profound disruption of membrane integrity, resulting in leakage of nucleic acids and proteins, extensive oxidative damage, hyperpolarization, and cell lysis, as confirmed by electron and confocal microscopy together with physicochemical assays. Mechanistic investigation revealed that oxidative damage from NaOCl amplified CA-induced membrane acidification and permeability, facilitating deeper sanitizer penetration and accelerating envelope destruction. Collectively, these findings uncover a membrane-targeted synergistic mechanism, providing a solid scientific basis for the development of novel, low-residue, and high-efficacy food safety interventions.

Upon the scalable utilization of polyphenols, the design of their composites with polymers has received a great deal of attention. However, the starch polymer has a weak loading of hydrophobic polyphenols typically through noncovalent interactions without biochemical catalysts. Here, we tailor a reticular starch nanostructure from a starch nanosphere precursor (preSNS) that traps ferulic acid (FA) via esterification. The preSNS-FA network is activated by a green physical method via dynamic high-pressure microfluidization, exhibiting an exceptionally higher content of FA (∼38.0%) compared with the conventional starch group (only ∼1.5%). SEM, FTIR, XRD, 13C NMR, 1H NMR, and XPS results as well as molecular dynamics simulation comprehensively confirm the changes in architecture and hydrogen bonding modes with the formation of -COOR-. The preSNS-FA network also has an enzymatic hydrolysis resistance (up to 83.8%). Collectively, this work establishes a high-performance and catalyst-free synthetic route toward an esterified polyphenol complex network with potential applications in nutrient delivery, food packaging, and agriculture fields.

Hydroponic cultivation of lettuce is an increasingly popular sustainable agricultural technique. However, Escherichia coli, a prevalent bacterium, poses significant concerns for the quality and safety of hydroponically grown lettuce. This study aimed to develop a growth model for E. coli and background microflora in hydroponically grown lettuce. The experiment involved inoculating hydroponically grown lettuce with E. coli and incubated at 4, 10, 15, 25, 30, 36 °C. Growth models for E. coli and background microflora were then developed using Origin 2022 (9.9) and IPMP 2013 software and validated at 5 °C and 20 °C by calculating root mean square errors (RMSEs). The result showed that E. coli was unable to grow at 4 °C and the SGompertz model was determined as the most appropriate primary model. From this primary model, the Ratkowsky square root model and polynomial model were derived as secondary models for E. coli-R168 and background microflora, respectively. These secondary models determined that the minimum temperature (T_min) required for the growth of E. coli and background microflora in hydroponically grown lettuce was 6.1 °C and 8.7 °C, respectively. Moreover, the RMSE values ranged from 0.11 to 0.24 CFU/g, indicating that the models and their associated kinetic parameters accurately represented the proliferation of E. coli and background microflora in hydroponically grown lettuce.

The widespread bacterial contamination caused by foodborne pathogens has continuously driven the development of advanced and potent food antimicrobial agents. In this study, two novel antimicrobial peptides (AMPs) named KTA and KTR were obtained by modifying a natural AMP, Leg2, from chickpea storage protein legumin hydrolysates. They were further predicted to be stable hydrophobic cationic AMPs of α-helical structure with no hemolytic toxicity by several online servers. Moreover, the AMPs exerted superior antibacterial activity against two representative Staphylococcus aureus strains thanks to the increased hydrophobicity and positive charge, with minimum inhibition concentration value (4.74-7.41 μM) significantly lower than that of Leg2 (>1158.70 μM). Further, this study sought to elucidate the specific antimicrobial mechanism against Gram-positive bacteria. It was found that the electrostatic interactions of the AMPs with peptidoglycan were vital for peptide activity in combating Gram-positive bacteria. Subsequently, the cell membrane of S. aureus cells was irreversibly disrupted by increasing permeability and impairing membrane components, which led to the massive release of intracellular substances and eventual cell death. Overall, this work demonstrated that KTA and KTR were active against Gram-positive bacteria via peptidoglycan targeting and membrane-disruptive mechanisms and paved the way for expanding their application potential to alleviate food contamination.

Antibacterial materials are urgently needed to combat bacterial contamination, growth, or attachment on contact surfaces, as bacterial infections remain a public health crisis worldwide. Here, a novel ultrasound-assisted method is utilized for the first time to fabricate oxidative chlorine-loaded AH@PBAT/PBF-Cl films with more superior grafting efficiency and rechargeable antibacterial effect than those from conventional techniques. The films remarkably inactivate 99.9999% Escherichia coli and Staphylococcus aureus cells, inducing noticeable cell deformations and mechanical instability. The specific antibacterial mechanism against E. coli used as a model organism is unveiled using several cell envelope structural and functional analyses combined with proteomics, peptidoglycomics, and fluorescence probe techniques. Film treatment partially neutralizes the bacterial surface charge, induces oxidative stress and cytoskeleton deformity, alters membrane properties, and disrupts the expression of key proteins involved in the synthesis and transport of the lipopolysaccharide and peptidoglycan, indicating the cell envelope as the primary target. The films specifically target lipopolysaccharides, resulting in structural impairment of the polysaccharide and lipid A components, and inhibit peptidoglycan precursor synthesis. Together, these lead to metabolic disorders, membrane dysfunction, structural collapse, and eventual death. Given the films' antibacterial effects via the disruption of key cell envelope components, they can potentially combat a wide range of bacteria. These findings lay a theoretical basis for developing efficient antibacterial materials for food safety or biomedical applications.