Divalent Cation Signaling in Clostridium perfringens Spore Germination

Synergistic inactivation and mechanism of thermosonication treatment combined with germinants and licorice extracts against Paraclostridium bifermentans

Spore contamination is a critical factor that contributes to food spoilage and economic losses in the food industry. In this study, we employed a "germination-inactivation-inhibition" strategy to effectively inactivate Paraclostridium bifermentans spores. We systematically screened and optimized the germinants, thermosonication conditions, and inhibitors to determine the most effective combination for spore inactivation. We found that the optimal conditions were germinant "A" GFNa-60 (90 mmol/L L-alanine, 10 mmol/L D-glucose, 10 mmol/L D-fructose, and 60 mmol/L NaCl), thermosonication (40 KHz, 480 W) at 80 °C for 60 min, and licorice extract (6.25 mg/mL) as an inhibitor. This combination was highly effective in deactivating P. bifermentans spores, resulting in a reduction of approximately 3.59 log CFU/mL. Detailed analyses, including particle size analysis, fluorescence microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), provided insights into the mechanisms underlying spore inactivation. Specifically, germinants decreased spore resistance, thermosonication induced spore surface expansion and perforation, and licorice extract facilitated spore dispersion while exacerbating thermosonication-induced inner membrane damage and nucleic acid leakage, leading to synergistic spore inactivation. Additionally, licorice extract continued to inhibit the growth and reproduction of the remaining spores. A spore inactivation rate of 99.97 % was achieved. These findings offer valuable insights into improved sterilization practices in the food industry, particularly for the management of spore contamination. The proposed "germination-inactivation-inhibition" strategy demonstrates potential as an effective approach for controlling spores in industrial applications.

Review of advances in molecular structure and biological function of alpha toxin of Clostridium perfringens

Alpha toxin has become the subject of research in recent years. The objective of this article was to review and summarize recent research on the molecular structure and biological function of the alpha toxin of Clostridium perfringens. This includes the work of our research team, as well as that of other researchers. Clostridium perfringens is an anaerobic, spore-forming, Gram-positive bacillus. It can cause various intestinal diseases, such as gas gangrene, food poisoning, non-foodborne diarrhea, and enteritis. Clostridium perfringens can be classified into 5 toxinotypes A, B, C, D, and E, based on the production of major toxins. Each type of C. perfringens produces alpha toxin, which is one of the most important lethal and dermonecrotic toxins and is considered a primary virulence factor. Alpha toxin is a multifunctional metalloenzyme with phospholipase C and sphingomyelinase activities that simultaneously hydrolyze phosphatidylcholine and sphingomyelin. It can therefore destroy the integrity of cell membranes and eventually cause cell lysis. The clinical effects of alpha toxins are characterized by cytotoxicity, hemolytic activity, lethality, skin necrosis, platelet aggregation, and increased vascular permeability. Future research will concentrate on the pathogenesis of a lpha toxin exposure, clarifying the interaction between alpha toxin and the cell membrane and investigating the mechanism of activating platelet function. This research will have substantial theoretical and practical value in controlling disease progression, identifying targeted therapeutic sites, and reducing the toxic effects of vaccines.

Optimization of degradation conditions and analysis of degradation mechanism for nitrite by Bacillus aryabhattai 47

Excessive nitrite levels cause significant damage to aquaculture, making it crucial to explore green and reliable nitrite removal technologies. In this study, A Bacillus aryabhattai (designated as the strain 47) isolated from aquaculture wastewater was used as the experimental strain. The nitrite degradation conditions of the strain 47 were optimized, and the optimal conditions are: glucose was 12.74 g/L, fermented special soybean meal was 21.27 g/L, MgCl2 369 mg/L, pH 7.0, incubated at 30 °C with the inoculum size of 2 % and the rotation speed of 170 rpm. Under the optimal conditions, the nitrite concentration of the culture solution was 200 mg/L, and the nitrite removal rate reached 91.4 %. Meanwhile, the mechanism by which Mg2+ enhanced the nitrite degradation ability of the strain 47 was investigated by transcriptomics. An operon structure directed cellular trafficking of Mg2+, and then, the Mg2+-mediated catalytic reaction of multiple enzymes enhanced and improved cellular metabolic processes (e.g. the transport and metabolism of nitrite, central carbohydrate metabolism oxidative phosphorylation). At the same time, with the progress of cell metabolism, cells secreted a series of enzymes related to nitrite transport and metabolism to promote the metabolism of nitrite. And the process of the assimilated nitrate reduction pathway of nitrite degradation in the strain 47 was elaborated at the transcriptome level. This study provided a new insight into nitrite treatment mediated by microbial organisms.