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Salmonella is a notoriously important pathogen that can cause human latent, acute, and chronic foodborne diseases. This work excavated a silver nanomaterial AgDAMP with a thiolate ligand as a novel composite bacteriostat to understand the inhibitory effects on Salmonella and to explore its antimicrobial mechanisms from the aspects of membrane structure damage, biofilm inhibition, and protein expression. The characterization results of its morphology, particle size, chemical bonds, elements, and crystal structure showed that AgDAMP were small-sized spherical nanoparticles with a certain crystallinity. AgDAMP could combat effectively the planktonic Salmonella, manifested as loss of membrane integrity, enhanced permeability, cytoplasmic leakage, and changes of cell morphology. Our study also suggested that AgDAMP not only significantly interfered with biofilm formation but also destroyed mature biofilm. Proteomic profiling indicated that the exposure to an inhibitory concentration of AgDAMP altered conspicuously more protein expression in Salmonella than a subinhibitory concentration. KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis revealed that differentially expressed proteins (DEPs) were primarily enriched in the ribosome, ABC transporters, and biosynthesis of secondary metabolite pathways. Furthermore, we found that AgDAMP significantly altered the expression of regulators associated with cellular DNA replication, protein synthesis, membrane transport, cell motility, and oxidative stress, which affected cell growth. These data provide new prospects for the responses of Salmonella to AgDAMP exposure, indicating that AgDAMP could be used as a novel nanotechnology for the treatment of foodborne pathogens. [ABSTRACT FROM AUTHOR]

Salt particles generated by aerosol generator are commonly used in air filtration test. As a common phenomenon, the number of generated particles increases with the salt concentration in the atomization solution. Thus far, the dependence of the particle number on the concentration of the atomization solution is not fully understood. In this study, two hypotheses were proposed to explain this phenomenon: i) a single droplet generates multiple solid particles, and the generated particle number is influenced by the salt concentration, and ii) the original droplet number increases with an increase in the salt concentration of the atomization solution. By observing the particle formation process of the levitated millimeter-scale NaCl droplet, one droplet was found to generate one particle in free air. However, whether these results are applicable to micrometer-scale droplets remains to be determined. In situ measurements were performed to detect the size distributions of the original droplets generated by the atomization solutions with various salt concentrations. A more concentrated atomization solution induced a higher number of original droplets. Particle formation patterns of droplets on glass substrates and filaments were demonstrated. Traditional observation methods for droplet drying are unsuitable for studying the particle formation of atomized droplets because of the large difference in droplet size and the existence of external forces. [ABSTRACT FROM AUTHOR]

The effect of barium ions on the biomineralization of calcium and magnesium ions is often overlooked when utilizing microbial-induced carbonate precipitation technology for removing barium, calcium, and magnesium ions from oilfield wastewater. In this study, Bacillus licheniformis was used to bio-precipitate calcium, magnesium, and barium ions. The effects of barium ions on the physiological and biochemical characteristics of bacteria, as well as the components of extracellular polymers and mineral characteristics, were also studied in systems containing coexisting barium, calcium, and magnesium ions. The results show that the increasing concentrations of barium ions decreased pH, carbonic anhydrase activity, and concentrations of bicarbonate and carbonate ions, while it increased the contents of humic acids, proteins, polysaccharides, and DNA in extracellular polymers in the systems containing all three types of ions. With increasing concentrations of barium ions, the content of magnesium within magnesium-rich calcite and the size of minerals precipitated decreased, while the full width at half maximum of magnesium-rich calcite, the content of O-C=O and N–C=O, and the diversity of protein secondary structures in the minerals increased in systems containing all three coexisting ions. Barium ions does inhibit the precipitation of calcium and magnesium ions, but the immobilized bacteria can mitigate the inhibitory effect. The precipitation ratios of calcium, magnesium, and barium ions reached 81–94%, 68–82%, and 90–97%. This research provides insights into the formation of barium-enriched carbonate minerals and offers improvements for treating oilfield wastewater. [ABSTRACT FROM AUTHOR]