Ferrous gluconate triggers ferroptosis in Escherichia coli: Implications of lipid peroxidation and DNA damage.

Microbial ferroptosis has been proved to combat drug-resistant pathogens, but whether this pattern can be applied to the prevention and control of Escherichia coli remains to be further explored. In this study, ferrous gluconate (FeGlu) showed remarkable efficacy in killing E. coli MG1655 with a mortality rate exceeding 99.9%, as well as enterotoxigenic E. coli H10407 (ETEC H10407) and enterohemorrhagic E. coli O157:H7 (EHEC O157:H7). Bacteria death was instigated by the infiltration of Fe2+, accompanied by a burst of intracellular reactive oxygen species (ROS) and lipid peroxidation. Notably, mitigating lipid peroxidation failed to alleviate death of E. coli. Further findings confirmed that FeGlu induced DNA damage, and ΔrecA mutant showed more sensitive, implicating that DNA damage was involved in the death of E. coli. The direct interaction of Fe2+ with DNA was demonstrated by fluorescent staining, gel electrophoresis, and circular dichroism (CD). Moreover, proteomic analysis unveiled 50 differentially expressed proteins (DEPs), including 18 significantly down-regulated proteins and 32 significantly up-regulated proteins. Among them, the down-regulation of SOS-responsive transcriptional suppressor LexA indicated DNA damage induced severely by FeGlu. Furthermore, FeGlu influenced pathways such as fatty acid metabolism (FadB, FadE), iron-sulfur cluster assembly (IscA, IscU, YadR), iron binding, and DNA-binding transcription, along with α-linolenic acid metabolism, fatty acid degradation, and pyruvate metabolism. These pathways were related to FeGlu stress, including lipid peroxidation and DNA damage. In summary, FeGlu facilitated ferroptosis in E. coli through mechanisms involving lipid peroxidation and DNA damage, which presents a new strategy for the development of innovative antimicrobial strategies targeting E. coli infections.

Ferrous sulphate triggers ferroptosis in Candida albicans and cures vulvovaginal candidiasis in a mouse model.

Candida albicans is the most leading cause of life-threatening fungal invasive infections, especially for vulvovaginal candidiasis (VVC). Resistance and tolerance to common fungicide has risen great demands on alternative strategies for treating C. albicans infections. In the present study, ferroptosis has been proven to occur in C. albicans by directly exposed to FeSO4 via induing hallmarks of ferroptosis, including Fe2+ overload burden, ROS eruption and lipid peroxidation. Transcriptomic profile gave the great hints of the possible mechanism for fungal ferroptosis that FeSO4 disturb pathways associated to ribosome, tyrosine metabolism, triglyceride metabolism and thiamine metabolism, thus mobilizing death-related gene synthesis. Inspired by the results, a FeSO4-loaded hydrogel was prepared as an antifungal agent to treat C. albicans infection. This hydrogel exhibited excellent dressing properties and maintained superior antifungal activity by characterization tests. Besides, mice treated by this composite hydrogel displayed excellent therapeutic efficacy. These results highlighted the potential therapeutic use of FeSO4 as an innovative strategy in treating C. albicans infections by targeting ferroptosis.

An "intelligent -responsive" bactericidal system based on OSA-starch Pickering emulsion.

Pickering emulsion based on OSA-starch was developed in this study as an intelligent delivery system for the application of thymol against foodborne pathogens. Morphology and microstructure characterization showed that the Pickering emulsion was an O/W type emulsion and stayed stable at starch concentration of 200 mg/mL and oil fraction at 30 % with particle size of 10 µm and absolute Zeta potential of -12.5 mV. Low field nuclear magnetic resonance and rheology experiments indicated that a denser network structure was formed in this stable Pickering emulsion. Besides, the Pickering emulsion could endure long-time storage, low pH (3,5) and additional NaCl (50, 100, 200, 400 mM) and it showed enhanced bactericidal effects against Escherichia coli, Staphylococcus aureus (thymol =1.48 µmol/L) and Aspergillus flavus (thymol = 0.624 µmol/L) by inducing ROS eruption, membrane lipid peroxidation and cell shrink. Moreover, the bactericidal assay demonstrated that thymol could be intelligently released and a considerable 75 % timely bactericidal effect was detected after 9 days' intermittently exposing to E. coli, S. aureus and A. flavus in vitro, by comparison thymol alone showed only 20 % bactericidal effect due to its volatility. The results are of great importance to offer an intelligent delivery system of bio-actives defending foodborne pathogens.

Fe2+ protects postharvest pitaya (Hylocereus undulatus britt) from Aspergillus. flavus infection by directly binding its genomic DNA.

Aspergillus flavus (A. flavus) is a postharvest fungus, causing pitaya fruit decay and limiting pitaya value and shelf life. However, safer and more efficient methods for preventing A. flavus contamination for pitaya fruit remain to be investigated. In this study, we successfully proved exogenous Fe2+ could inhibit A. flavus colonization in pitaya fruit and extend pitaya's shelf life after harvest. Moreover, gel electrophoresis, CD analysis and Raman spectrum tests revealed Fe2+ could more effectively and thoroughly promote conidial death by directly binding to A. flavus DNA. Increased expression of DNA damage repair-related genes after Fe2+ treatment was observed by transcription analysis, which might eventually lead to SOS response in A. flavus. These results indicated Fe2+ could prevent A. flavus infestation on pitaya in a novel, quickly responsive mechanism. Our results shed light on the potential application of Fe2+ in the food industry and provided a more universal antifungal agent against food pathogens.

Exogenous Iron Induces NADPH Oxidases-Dependent Ferroptosis in the Conidia of Aspergillus flavus.

Aspergillus flavus is saprophytic soil fungus that contaminates seed crops with the carcinogenic secondary metabolite aflatoxin, posing a significant threat to humans and animals. Ferrous sulfate is a common iron supplement that is used to the treatment of iron-deficiency anemia. Here, we identified an unexpected inhibitory role of ferrous sulfate on A. flavus. With specific fluorescent dyes, we detected several conidial ferroptosis hallmarks in conidia under the treatment of 1 mM Fe2+, including nonapoptosis necrosis, iron-dependent, lipid peroxide accumulation, and ROS burst. However, unlike traditional ferroptosis in mammals, Fe2+ triggered conidial ferroptosis in A. flavus was regulated by NADPH oxidase (NOXs) activation instead of Fenton reaction. Transcriptomic and some other bioinformatics analyses showed that NoxA in A. flavus might be a potential target of Fe2+, and thus led to the occurrence of conidial ferroptosis. Furthermore, noxA deletion mutant was constructed, and both ROS generation and conidial ferroptosis in ΔnoxA was reduced when exposed to Fe2+. Taken together, our study revealed an exogenous Fe2+-triggered conidial ferroptosis pathway mediated by NoxA of A. flavus, which greatly contributes to the development of an alternative strategy to control this pathogen.

EGCG Alleviates Oxidative Stress and Inhibits Aflatoxin B1 Biosynthesis via MAPK Signaling Pathway.

Aflatoxin biosynthesis has established a connection with oxidative stress, suggesting a prevention strategy for aflatoxin contamination via reactive oxygen species (ROS) removal. Epigallocatechin gallate (EGCG) is one of the most active and the richest molecules in green tea with well-known antioxidant effects. Here, we found EGCG could inhibit aflatoxin B1 (AFB1) biosynthesis without affecting mycelial growth in Aspergillus flavus, and the arrest occurred before the synthesis of toxin intermediate metabolites. Further RNA-seq analysis indicated that multiple genes involved in AFB1 biosynthesis were down-regulated. In addition, EGCG exposure facilitated the significantly decreased expression of AtfA which is a bZIP (basic leucine zipper) transcription factor mediating oxidative stress. Notably, KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis indicated that the MAPK signaling pathway target transcription factor was down-regulated by 1 mg/mL EGCG. Further Western blot analysis showed 1 mg/mL EGCG could decrease the levels of phosphorylated SakA in both the cytoplasm and nucleus. Taken together, these data evidently supported that EGCG inhibited AFB1 biosynthesis and alleviated oxidative stress via MAPK signaling pathway. Finally, we evaluated AFB1 contamination in soy sauce fermentation and found that EGCG could completely control AFB1 contamination at 8 mg/mL. Conclusively, our results supported the potential use of EGCG as a natural agent to prevent AFB1 contamination in fermentation industry.