Qiuying Li,Chenyang Jia,Jiaxing Sun,Tong Sun,Jianrong Li,Xuepeng Li
The strong spoilage capability and cold adaptability of Shewanella putrefaciens present a serious threat to the quality and safety of fish. This study aimed to investigate the synergic antibacterial effects of six phenolic acids (Gallic acid, GA; Caffeic acid, CA; Protocatechuic acid; Ferulic acid; Chlorogenic acid; p-Coumaric acid) in pairs against S . putrefaciens , and to illustrate the antibacterial mechanisms. The fractional inhibitory concentration index (FICI) of 15 combinations of phenolic acids against S. putrefaciens ranged from 0.5-0.75, suggesting synergistic or partial synergistic antibacterial effects of these phenolic acids. Time-kill curves and morphologic observation demonstrated that GA and CA (GC) exhibited the strongest synergistic effect against S. putrefaciens . GC synergistically damaged the structure integrity of S. putrefaciens , leading to the leakage of intracellular substances and inhibiting the activity of Na + K + -ATPase and respiratory chain dehydrogenase. Both GA and CA could bind to DNA and cause changes in DNA content. Proteomics analysis revealed that 399 proteins were affected in the GC groups, a number significantly higher than that in the single GA and CA groups. GC inhibited dissimilatory nitrate and sulfate reduction, and enhanced fatty acid degradation and assimilatory sulfate reduction, which might cause the imbalance of energy supply and ROS accumulation. Meanwhile, the antioxidant-related enzymes, efflux systems and some two-components systems were upregulated, while chemotaxis were inhibited. GC synergistically inhibited S. putrefaciens in turbot, and retarded the spoilage process. The results revealed multi-targeted synergistic antibacterial mechanisms of GC against S. putrefaciens , suggesting GC might be a good strategy for controlling S. putrefaciens and fish spoilage.
Cell’s activities are highly dependent on signal molecules, of which reactive oxygen species of the superoxide anion (O2•–) and hydrogen peroxide (H2O2) are important ones that always work together to regulate biological processes such as apoptosis and oxidative stress. It is of significance to realize simultaneous qualification of O2•– and H2O2 but it still faces challenges particularly in live-cell assay with a complex environment. We report the design of a bifunctional sensing material by interfacially regulating ZIF-67 on bacteria Shewanella putrefaciens to generate cobalt nanoparticles/nitrogen-doped porous carbon nanorods (Co/N-doped CNRs) and its sensing chip for qualifying cell-released O2•– and H2O2. Co/N-doped CNRs exhibit unique properties including porous structure for significantly increased reaction surface area and coordinating Co nanoparticles for rich active sites. The bifunctional Co/N-doped CNRs is used to fabricate the electrochemical sensing chip, which achieves a fast response time (0.5 s for O2•–, 1.9 s for H2O2), a low detection limit (0.69 nM for O2•–, 2.25 μM for H2O2), and a remarkably high sensitivity (792.30 μA·μM–1·cm–2 for O2•–, 153.91 μA·mM–1·cm–2 for H2O2), among the best of reported bifunctional nanozymes.
This study aimed to investigate the mechanism underlying the synergistic antimicrobial effect of ferulic acid (FA) and ε-polylysine hydrochloride (PL) on Shewanella putrefaciens (S. putrefaciens) and their application on crayfish (Procambarus clarkii). The treatment with FA and PL exhibited a strong synergistic inhibitory effect against S. putrefaciens. The combination of 1/4 Minimum Inhibitory Concentration (MIC) FA and 1/4 MIC PL was the most effective, damaging the cell structure and inhibiting the growth ofS. putrefaciens. Plasma-activated water (PAW) can induce microbial inactivation through physical action. In addition, treatments with FA, PL, PAW, PAW-FA, PAW-PL, and PAW + PL-FA substantially decreased total viable counts (TVCs), total volatile base nitrogen (TVB-N), the thiobarbituric acid value (TBA), and the juice loss rate of crayfish, with FA-PL showing the best effect. This study confirmed the antimicrobial efficacy of PL, FA, and PAW, indicating their potential as effective preservatives for controlling spoilage in freshwater crustaceans.
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