Over time, the proportion of resistant bacteria will increase. This is a major concern. Therefore, effective and biocompatible therapeutic strategies against these bacteria are urgently needed. Non-thermal plasma has been exhaustively characterized for its antibacterial activity. This study aims to investigate the inactivation efficiency and mechanisms of plasma-generated nitric oxide water (PG-NOW) on pathogenic water, air, soil, and foodborne Gram-negative and Gram-positive bacteria. Using a colony-forming unit assay, we found that PG-NOW treatment effectively inhibited the growth of bacteria. Moreover, the intracellular nitric oxide (NO) accumulation was evaluated by 4-amino-5-methylamino-2′,7′-dichlorofluorescein diacetate (DAF-FM DA) staining. The reduction of viable cells unambiguously indicates the anti-microbial effect of PG-NOW. The soxR and soxS genes are associated with nitrosative stress, and oxyR regulation corresponds to oxidative stress in bacterial cells. To support the nitrosative effect mediated by PG-NOW, we have further assessed the soxRS and oxyR gene expressions after treatment. Accordingly, soxRS expression was enhanced, whereas the oxyR expression was decreased following PG-NOW treatment. The disruption of cell morphology was observed using scanning electron microscopy (SEM) analysis. In conclusion, our findings furnish evidence of an initiation point for the further progress and development of PG-NOW-based antibacterial treatments.

Cold-active enzymes increase their catalytic efficiency at low-temperature, introducing structural flexibility at or near the active sites. Inevitably, this feat seems to be accompanied by lower thermal stability. These characteristics have made cold-active enzymes into attractive targets for the industrial applications, since they could reduce the energy cost in the reaction, attenuate side-reactions, and simply be inactivated. In addition, the increased structural flexibility could result in broad substrate specificity for various non-native substrates, which is called substrate promiscuity. In this perspective, we deal with a less addressed aspect of cold-active enzymes, substrate promiscuity, which has enormous potential for semi-synthesis or enzymatic modification of fine chemicals and drugs. Further structural and directed-evolutional studies on substrate promiscuity of cold-active enzymes will provide a new workhorse in white biotechnology.

In this work, solar-light-active copper–vanadium oxide (Cu-VO) was synthesized by a simple microwave method and characterized by FESEM, EDS, XRD, XPS, UV–Vis/near-infrared (NIR), and FT-IR spectroscopy. Antialgal and dye degradation activities of Cu-VO were investigated against Microcystis aeruginosa and methylene blue dye (MB), respectively. The mechanism of action of Cu-VO was examined regarding the production of hydroxyl radical (·OH) in the medium and intracellular reactive oxygen species (ROS) in M. aeruginosa. FESEM and XRD analyses of Cu-VO disclosed the formation of monoclinic crystals with an average diameter of 132 nm. EDX and XPS analyses showed the presence of Cu_, V_, and O atoms on the surface of Cu-VO. Furthermore, FT-IR analysis of Cu-VO exposed the presence of tetrahedral VO₄ and octahedral CuO₆. Cu-VO effectively reduced the algal growth and degraded methylene blue under solar light. A total of 4 mg/L of Cu-VO was found to be effective for antialgal activity. Cu-VO degraded 93% of MB. The investigation of the mechanism of action of Cu-VO showed that ·OH mediated antialgal and dye degradation of M. aeruginosa and MB. Cu-VO also triggered the production of intracellular ROS in M. aeruginosa, leading to cell death. Thus, Cu-VO could be an effective catalyst for wastewater treatment.

Liver-expressed antimicrobial peptides (LEAPs) are cysteine-containing cationic peptides. LEAP-1 and LEAP-2 are eight- and four-cysteine containing antimicrobial peptides found in animals, respectively. LEAP-1 is widely known as antibacterial peptide involved in the innate immunity of fish, but the roles of LEAP-1 and LEAP-2 in Antarctic fish species are unknown. In the present study, we synthesized and characterized novel LEAPs with four and eight cysteine residues, derived from Antarctic notothenioid (Dissostichus mawsoni) and Antarctic eelpout (Lycodichthys dearborni). Circular dichroism spectroscopy of these peptides showed a typical β-sheet conformation. The LEAPs were found to be bactericidal against gram-positive as well as gram-negative bacteria. In the SYTOX green uptake assay, LEAPs did not trigger any significant increase in fluorescence. However, LEAPs competitively bound to DNA and replaced the ethidium bromide (EB) dye. To determine the effect of temperature on the activity of LEAPs, we evaluated the antibacterial activity against Listeria monocytogenes at 5, 15, 25, and 35 °C. The results showed that the antibacterial activity of LEAPs increased with a decrease in temperature, which may indicate that the Antarctic fish LEAP are evolutionarily adapted. Taken together, our results suggest that novel Antarctic LEAPs are bactericidal peptides with the likely mode of action being DNA binding and may be evolved to adapt to cold temperature.

In this study, we attempted to synthesize visible light active nano-sized photocatalysts using metal oxides such as zinc oxide, zirconium oxide, tungsten oxide, and strontium titanium oxide with (MoCl₅)₂ as a dopant by the simple ball-milling method. Fourier-transform infrared spectroscopy data confirmed the presence of M-O-Mo linkage (M = Zn, Zr, W, and SrTi) in all the molybdenum-doped metal oxides (MoMOs), but only MoZnO inhibited the growth of the bloom-forming Microcystis aeruginosa under visible light in a concentration-dependent manner up to 10 mg/L. Further, structural characterization of MoZnO using FESEM and XRD exhibited the formation of typical hexagonal wurtzite nanocrystals of approximately 4 nm. Hydroxyl radical (·OH), reactive oxygen species (ROS), and lipid peroxidation assays revealed ·OH generated by MoZnO under the visible light seemed to cause peroxidation of the lipid membrane of M. aeruginosa, which led to an upsurge of intracellular ROS and consequently introduced the agglomeration of cyanobacteria. These results demonstrated that nano-sized MoZnO photocatalyst can be easily synthesized in a cost-effective ball-mill method and utilized for biological applications such as the reduction of harmful algal blooms. Further, our study implies that a simple ball-milling method can provide an easy, green, and scalable route for the synthesis of visible light active doped metal oxides.