Plasma-activated water (PAW) indicated promising potential in controlling the biological contamination of Bacillus cereus, which eliminated its evolutionary endospore that improves its survival ability. However, the spore inactivation mechanism by PAW at molecular level was not well understood. The mechanism of the Bacillus cereus endospore against PAW at proteomic levels was demonstrated. The Tandem Mass Tag (TMT) labeling was performed. By comparing the treatment groups with control (including PAW and PAW added superoxide dismutase (SOD)) , the expression of 251 proteins (with the number of 207 up- and 44 down-regulated) and 379 proteins (with the corresponding number of 238 and 141) were drastically affected, separately. The six categories based on the protein-protein interaction (PPI) networks included oxidation-reduction, transport, sporulation and DNA topological change, gene expression, metabolism, and others. The three dehydrogenases (Gene hisD, BC_2176, and asd) in PAW while oxidoreductase (Gene BC_0399 and BC_2529) in SOD were activated to maintain the antioxidation of spores. The proteins (BC_4271 and BC_2655) in SOD were dramatically activated, which were involved in the carbohydrate, amino acid, and energy-coupling transport. All the small, acid-soluble spore proteins were activated in both groups to protect the spores’ DNA. In SOD, genes metG2 and rpmC also were considered important factors in translation while this role was played in gene groES but not rpmF in PAW. The PAW activated the biogenesis of cell wall/membrane/envelope and phosphorelay signal transduction system to contribute to the survival of spores whereas the SOD damaged these two processes as well as cell division, chromosome separation, organic acid phosphorylation, base- and nucleotide-excision repair to lead to the death of spores. This would promise to lay the foundation for advancing the study of the intrinsic mechanism of spore killing against PAW and can also provide a reference for future verification.

Drinking water disinfection is an essential process to assure public health all over the world. In this study, silver nanoparticles (AgNPs) on UiO-66 (Zr) Metal-Organic Frameworks (Ag@UiO-66) is proposed as a potential water disinfection strategy. AgNPs are synthesized using polyvinyl pyrrolidone (PVP) as stabilizing agent, and sodium borohydride as reducing agent are subsequently embedded on UiO-66, a high-stability organometallic framework. The effect of premixing time, reaction time and reactant concentration on the loading rate of AgNPs on UiO-66 was investigated. The maximum load rate of AgNPs on UiO-66 could reach 13% when the premixing time is 3 h, the reaction time is 45 min and the concentration of AgNO₃ is 10μg/mL. The formation of AgNPs loaded on UiO-66 was observed and confirmed with ultraviolet and visible spectrophotometry (UV-Vis), scanning electron microscopy (SEM), infrared emission spectroscopy (IES) and X-ray diffraction (XRD) analysis. Ag@UiO-66 exhibited strong antibacterial activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, with minimum inhibitory concentrations (MIC) of 64 and 128μg/mL, respectively. The germicidal efficacy of Ag@UiO-66 enhanced significantly as the temperature rose from 4 ℃ to 37 ℃. The results indicate that Ag@UiO-66 is potential candidate as a feasible water disinfection material.

Ultrasound, is thought to a potential non-thermal sterilization technology in food industry. However, the exact mechanisms underlying microbial inactivation by ultrasound still remain obscure. In this study, the action modes of ultrasound on both Gram-negative and Gram-positive microorganisms were estimated. From colony results, ultrasound acted as an irreversible effect on both Eshcerichia coli and Staphylococcus aureus without sublethal injury. The result in this study also showed that a proportion of bacteria subpopulation suffered from serious damage of intracellular components (e.g. DNA and enzymes) but with intact cell envelopes. We speculated that the inactivated effects of ultrasound on microbes might more than simply completed disruption of cell exteriors. Those microbial cells who had not enter the valid area of ultrasonic cavitation might be injected with free radicals produced by ultrasound and experienced interior injury with intact exterior structure, and others who were in close proximity to the ultrasonic wave field would be immediately and completely disrupted into debris by high power mechanic forces. These findings here try to provide extension for the inactivation mechanisms of ultrasound on microorganisms.