Key biological processes and essential genes for Proteus mirabilis biofilm development inhibition by protocatechuic acid.

Proteus mirabilis is an opportunistic pathogen linked to human urinary tract infections, and is potentially present as a foodborne pathogen within poultry products, including broiler chickens. This report outlines the inhibitory impacts of protocatechuic acid (PCA) on P. mirabilis isolated from a broiler slaughterhouse in China as well as its biofilm. This investigation encompasses assays related to motility and adhesion, bacterial metabolic activity, extracellular polymer (EPS) production, and scavenging capacity. The findings demonstrated that PCA reduced biofilm formation by 61 %. Transcriptomics findings identified that PCA limited the expression of genes like PstS that promote adhesin formation, rbsA and RcsB that alter bacterial chemotaxis, lipopolysaccharide synthesis genes LpxA and EptB, and cell wall synthesis genes MurF and MrdA, and affects the Regulator of Capsule Synthesis (RCS) two-component modulation system. Weighted gene co-expression network analysis (WGCNA) was conducted to identify the core genes. Furthermore, the binding sites of PCA to cytochrome oxidases cydA and cydB, two subunits of ATP synthase atpI and atpH, and ftsZ, which regulate bacterial division, were predicted via molecular docking. Metabolome analysis determined that PCA critically influenced coenzyme A biosynthesis, nucleotide metabolism, alanine, aspartic acid, and glutamate metabolic pathways of P. mirabilis. Therefore, PCA impacts metabolism within bacteria via various pathways, limiting the levels of extracellular polymer and bacterial viability to hinder biofilm formation. Additionally, we prepared an antibacterial plastic film containing protocatechuic acid using PVA as the monomer and CNC as the reinforcing agent. We examined the mechanical and antibacterial properties of this film. When used to wrap chicken, it reduced the total number of colonies, slowed the deterioration of chicken, and maintained the freshness of chicken. In conclusion, the information outlined in this study complements our comprehension of P. mirabilis inhibition by PCA and provides clues for the reduction of foodborne infections associated with P. mirabilis.

Transcriptome Analysis of Protocatechualdehyde against Listeria monocytogenes and Its Effect on Chicken Quality Characteristics.

The development of natural antimicrobial agents offers new strategies for food preservation due to the health hazards associated with the spoilage of meat products caused by microbial contamination. In this paper, the inhibitory mechanism of protocatechualdehyde (PCA) on Listeria monocytogenes was described, and its effect on the preservation of cooked chicken breast was evaluated. The results showed that the minimal inhibitory concentration (MIC) of PCA on L. monocytogenes was 0.625 mg/mL. Secondly, PCA destroyed the integrity of the L. monocytogenes cell membrane, which was manifested as a decrease in membrane hyperpolarization, intracellular ATP level, and intracellular pH value. Field emission gun scanning electron microscopy (FEG-SEM) observed a cell membrane rupture. Transcriptome analysis showed that PCA may inhibit cell growth by affecting amino acid, nucleotide metabolism, energy metabolism, and the cell membrane of L. monocytogenes. Additionally, it was discovered that PCA enhanced the color and texture of cooked chicken breast meat while decreasing the level of thiobarbituric acid active substance (TBARS). In conclusion, PCA as a natural antibacterial agent has a certain reference value in extending the shelf life of cooked chicken breast.

Membrane damage mechanism of protocatechualdehyde against Micrococcus luteus and its effect on pork quality characteristics.

This study investigated the mechanism of membrane damage by protocatechualdehyde (PCA) against Micrococcus luteus and assessed effects of PCA on the sensory and physicochemical properties of pork. The mechanism of PCA inhibition on M. luteus was studied by determining the minimum inhibitory concentration (MIC) based on membrane potential, intracellular ATP concentration, intracellular pH, confocal laser scanning microscopy (CLSM), and field emission gun scanning electron microscopy (FEG-SEM). The results showed that the MIC of PCA against M. luteus was 1.25 mg/mL. Hyperpolarization of the bacterial cell membrane, a decrease in the intracellular ATP concentration, and intracellular pH indicated that PCA damaged the cell membrane of M. luteus. FEG-SEM observation revealed that PCA could cause surface collapse, cell membrane rupture, and content outflow of M. luteus. Additionally, PCA was found to inhibit increases in the total number of colonies, the thiobarbituric acid reactive substances (TBARS) value growth rate, and moisture mobility in raw pork. Additionally, it improved the color and texture of raw pork, all of which effectively prolonged its shelf life. This study will encourage the application of PCA as a natural antibacterial agent in the food industry.

Metabolomics analysis and membrane damage measurement reveal the antibacterial mechanism of lipoic acid against Yersinia enterocolitica.

Yersinia enterocolitica is a pathogenic microorganism that can cause food-borne diseases. Lipoic acid (LA) has been used as an antioxidant against bacteria, but its antibacterial mechanism is rarely reported. This study aims to explore the antibacterial mechanism of LA and its effect on the metabolites of Y. enterocolitica through membrane damage and metabolomics analysis. The results showed that the minimum inhibitory concentration (MIC) of LA against Y. enterocolitica was 2.5 mg mL-1. The membrane potential was depolarized, and intracellular pH (pHin) and ATP were significantly reduced, indicating that LA destroys the cell membrane structure. Confocal laser scanning microscopy (CLSM) and field emission scanning electron microscopy (FESEM) further confirmed LA-induced cell membrane damage. The metabolic profile of Y. enterocolitica following LA treatment was analyzed by liquid chromatography-mass spectrometry (LC-MS). In the metabolome evaluation, 6209 differential metabolites were screened, including 3394 up-regulated and 2815 down-regulated metabolites. Fifteen metabolic pathways of Y. enterocolitica exhibited significant changes after LA treatment, including the pathways important for amino acid and nucleotide metabolism. The results show that LA is a bacteriostatic substance with potential application value in the food industry.

Evaluation of gallic acid on membrane damage of Yersinia enterocolitica and its application as a food preservative in pork.

This study was aimed to examine the membrane damage mechanism of gallic acid (GA) on Yersinia enterocolitica BNCC 108930, and to explore whether GA can prolong the shelf life of pork. The minimal inhibitory concentration (MIC) of GA against Y. enterocolitica was determined by adopting the broth microdilution method. Second, an investigation was conducted on the morphological and physiological variations of Y. enterocolitica after the GA treatment. Finally, a response surface approach was used to establish the growth inhibition model of GA against Y. enterocolitica in pork. The MIC of GA against Yersinia enterocolitica BNCC 108930 was 2.5 mg/mL. GA affects the membrane integrity of Y. enterocolitica, as demonstrated by a significant decrease in intracellular ATP and pH. The results showed that the number of Y. enterocolitica in pork meat containing 5 mg/g of GA decreased by 2 logarithmic cycles during storage at 4 °C for 3 days. According to the obtained findings, GA could be used as a food preservative to prolong the shelf life of pork.