Contamination with pathogenic and infectious viruses severely threatens human health and animal husbandry. Current methods for disinfection have different disadvantages, such as inconvenience and contamination of disinfection by-products (e.g., chlorine disinfection). In this study, atmospheric surface plasma in argon mixed with air and plasma-activated water was found to efficiently inactivate bacteriophages, and plasma-activated water still had strong antiviral activity after prolonged storage. Furthermore, it was shown that bacteriophage inactivation was associated with damage to nucleic acids and proteins by singlet oxygen. An understanding of the biological effects of plasma-based treatment is useful to inform the development of plasma into a novel disinfecting strategy with convenience and no by-product.

Air plasma is commonly used to treat water for activation or purification, and plasma-activated water (PAW) is a promising green disinfectant that has attracted much attention in recent years. However, either the O ₃ discharge mode or the NO _x discharge mode of air plasma lacks efficiency for water activation, mainly due to the low solubility of O ₃ , NO and NO ₂ . The transition process between those two modes could produce high-valence NO _x such as N ₂ O ₅ which should be more efficient for water activation, but this process is not easily controlled and water activation by N ₂ O ₅ has rarely been reported before. In this letter, N ₂ O ₅ is found to be produced effectively and stably by mixing the effluent gases of a NO _x mode air plasma, produced by gliding arc discharge, and an O ₃ mode air plasma, produced by dielectric barrier discharge. The mixed gas rich in N ₂ O ₅ is found to be very efficient for water activation. A colony-forming unit reduction of nearly 6 logs was achieved for a methicillin-resistant Staphylococcus aureus suspension by using PAW treated by the mixed gas, and the high bactericidal effect of the PAW could persist for more than 1 h after the plasma activation. The main reactive species for the bactericidal effect in the PAW are discussed, and the chemical pathways for N ₂ O ₅ production and its usage for water activation are illustrated.

Red swamp crayfish (Procambarus clarkii) breeding is an important economic mainstay in Hubei province, China. However, information on the gut microbiota of the red swamp crayfish is limited. To address this issue, the effect of developmental stage, diet (fermented or non-fermented feed), and geographical location on the gut microbiota composition in the crayfish was studied via high-throughput 16S rRNA gene sequencing. The results revealed that the dominant phyla in the gut of the crayfish were Proteobacteria, Bacteroidetes,Firmicutes, Tenericutes, and RsaHF231. The alpha diversity showed a declining trend during development, and a highly comparable gut microbiota clustering was identified in a development-dependent manner. The results also revealed that development, followed by diet, is a better key driver for crayfish gut microbiota patterns than geographical location. Notably, the relative abundance of Bacteroidetes was significantly higher in the gut of the crayfish fed with fermented feed than those fed with non-fermented feed, suggesting the fermented feed can be important for the functions (e.g., polysaccharide degradation) of the gut microbiota. In summary, our results revealed the factors shaping gut microbiota of the crayfish and the importance of the fermented feed in crayfish breeding.

Reactive oxygen and nitrogen species (ROS and RNS) generated by cold atmospheric-pressure plasma could damage genomic DNA, although the precise types of these DNA damage induced by plasma are poorly characterized. Understanding plasma-induced DNA damage will help to elucidate the biological effect of plasma and guide the application of plasma in ROS-based therapy. In this study, it was shown that ROS and RNS generated by physical plasma could efficiently induce DNA-protein crosslinks (DPCs) in bacteria, yeast, and human cells. An in vitro assay showed that plasma treatment resulted in the formation of covalent DPCs by activating proteins to crosslink with DNA. Mass spectrometry and hydroperoxide analysis detected oxidation products induced by plasma. DPC formation were alleviated by singlet oxygen scavenger, demonstrating the importance of singlet oxygen in this process. These results suggested the roles of DPC formation in DNA damage induced by plasma, which could improve the understanding of the biological effect of plasma and help to develop a new strategy in plasma-based therapy including infection and cancer therapy.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of serious nosocomial infections, and recurrent MRSA infections primarily result from the survival of persister cells after antibiotic treatment. Gas plasma, a novel source of ROS (reactive oxygen species) and RNS (reactive nitrogen species) generation, not only inactivates pathogenic microbes but also restore the sensitivity of MRSA to antibiotics. This study further found that sublethal treatment of MRSA with both plasma and plasma-activated saline increased the antibiotic sensitivity and promoted the eradication of persister cells by tetracycline, gentamycin, clindamycin, chloramphenicol, ciprofloxacin, rifampicin, and vancomycin. The short-lived ROS and RNS generated by plasma played a primary role in the process and induced the increase of many species of ROS and RNS in MRSA cells. Thus, our data indicated that the plasma treatment could promote the effects of many different classes of antibiotics and act as an antibiotic sensitizer for the treatment of antibiotic-resistant bacteria involved in infectious diseases.

N₂O₅, a reactive species produced by air discharge plasma, has recently attracted much attention. Due to its high reactivity and solubility, N₂O₅ is a key molecule in nitrogen fixation processes and exhibits promising prospects in plasma biomedicine. However, thus far, it is not well known how to produce N₂O₅ efficiently and then maintain its concentration under the action of fast removal reactions. In view of this, N₂O₅ production by dielectric barrier discharge (DBD) alone and by the combination of DBD and gliding arc discharge is compared in this paper. It is found that the combination method can yield over three times the concentration of N₂O₅ compared to the single DBD method with the optimum discharge power. Moreover, the concentration of N₂O₅ in the effluent gas can be maintained once O₃ also exists because O₃ can continually produce N₂O₅ to compensate for its reduction. Finally, the sterilization effects of both the plasma effluent gas and plasma-activated water have trends similar to the trend of the gaseous N₂O₅ concentration, implying that N₂O₅ plays an important role in sterilization. This paper enhances the understanding of N₂O₅ chemistry in air discharge plasma and provides an effective way to produce and maintain N₂O₅ for subsequent applications.