Urechistachykinin I induced ferroptosis by accumulating reactive oxygen species in Vibrio vulnificus

Antimicrobial peptides (AMPs), such as urechistachykinin I (LRQSQFVGSR-NH2), derived from urechis unicinctus, have demonstrated antimicrobial activities. It exhibits low cytotoxicity and selectivity between microbial and mammalian cells suggesting its potent antimicrobial ability. However, the underlying antimicrobial mechanisms remain unknown. Herein, we elucidated the antibacterial action against Vibrio vulnificus, focusing on the reactive oxygen species (ROS). ROS is crucial for antibiotic-mediated killing and oxidative stress. After treatment with urechistachykinin I, superoxide anions and hydroxyl radicals increase, and the overproduction of ROS leads to oxidative damage and destruction of the redox system. Oxidation of the defense system like glutathione or glutathione peroxidase 4 illustrates the dysfunction of cellular metabolism and induces lipid peroxidation attributed to depolarization and integrity brokerage. Cell death demonstrated these properties, and additional experiments, including iron accumulation, liperfluo, and DNA fragmentation, were promoted. The results demonstrated that urechistachykinin I-induced ferroptosis-like death in Vibrio vulnificus is dependent on ROS production. KEY POINTS: • Urechistachykinin I induce reactive oxygen species production • Urechistachykinin I cause oxidative damaged on the V. vulnificus • Urechistachykinin I ferroptosis-like death in V. vulnificus.

Ferroptosis-Like Death in Microorganisms: A Novel Programmed Cell Death Following Lipid Peroxidation

Ferroptosis is a new kind of programmed cell death of which occurrence in microorganisms is not clearly verified. The elevated level of reactive oxygen species (ROS) influences cellular metabolisms through highly reactive hydroxyl radical formation under the iron-dependent Fenton reaction. Iron contributes to ROS production and acts as a cofactor for lipoxygenase to catalyze poly unsaturated fatty acid (PUFA) oxidation, exerting oxidative damage in cells. While ferroptosis is known to take place only in mammalian cells, recent studies discovered the possible ferroptosis-like death in few specific microorganisms. Capacity of integrating PUFA into intracellular membrane phospholipid has been considered as a key factor in bacterial or fungal ferroptosis-like death. Vibrio species in bacteria and Saccharomyces cerevisiae in fungi exhibited certain characteristics. Therefore, this review focus on introducing the occurrence of ferroptosis-like death in microorganisms and investigating the mode of action underlying the cells based on contribution of lipid peroxidation and iron-dependent reaction.

Long-term transformation of nanoscale zero-valent iron explains its biological effects in anaerobic digestion: From ferroptosis-like death to magnetite-enhanced direct electron transfer networks

Nanoscale zero-valent iron (nZVI) has been extensively used for environmental remediation and wastewater treatment. However, the biological effects of nZVI remain unclear, which is no doubt a result of the complexity of iron species and the dynamic succession of microbial community during nZVI aging. Here, the aging effects of nZVI on methanogenesis in anaerobic digestion (AD) were consecutively investigated, with an emphasis on deciphering the causal relationships between nZVI aging process and its biological effects. The addition of nZVI in AD led to ferroptosis-like death with hallmarks of iron-dependent lipid peroxidation and glutathione (GSH) depletion, which inhibited CH₄ production during the first 12 days of exposure. With prolonged exposure time, a gradual recovery (12-21 days) and even better performance (21-27 days) in AD were observed. The recovery performance of AD was mainly attributed to nZVI-enhanced membrane rigidity via forming siderite and vivianite on the outer surface of cells, protecting anaerobes against nZVI-induced toxicity. At the end of 27-days exposure, the significantly increased amount of conductive magnetite simulated direct interspecies electron transfer among syntrophic partners, improving CH₄ production. Metagenomic analysis further revealed that microbial cells gradually adapted to the aging of nZVI by upregulating functional genes related to chemotaxis, flagella, conductive pili and riboflavin biosynthesis, in which electron transfer networks likely thrived and the cooperative behaviors between consortium members were promoted. These results unveiled the significance of nZVI aging on its biological effects toward multiple microbial communities and provided fundamental insights into the long-term fates and risks of nZVI for in situ applications.