Catalytic Properties of Flavocytochrome c Sulfide Dehydrogenase from Haloalkaliphilic Bacterium Thioalkalivibrio paradoxus

Quantitative proteomics reveals the Sox system's role in sulphur and arsenic metabolism of phototroph Halorhodospira halophila

The metabolic process of purple sulphur bacteria's anoxygenic photosynthesis has been primarily studied in Allochromatium vinosum, a member of the Chromatiaceae family. However, the metabolic processes of purple sulphur bacteria from the Ectothiorhodospiraceae and Halorhodospiraceae families remain unexplored. We have analysed the proteome of Halorhodospira halophila, a member of the Halorhodospiraceae family, which was cultivated with various sulphur compounds. This analysis allowed us to reconstruct the first comprehensive sulphur-oxidative photosynthetic network for this family. Some members of the Ectothiorhodospiraceae family have been shown to use arsenite as a photosynthetic electron donor. Therefore, we analysed the proteome response of Halorhodospira halophila when grown under arsenite and sulphide conditions. Our analyses using ion chromatography-inductively coupled plasma mass spectrometry showed that thioarsenates are chemically formed under these conditions. However, they are more extensively generated and converted in the presence of bacteria, suggesting a biological process. Our quantitative proteomics revealed that the SoxAXYZB system, typically dedicated to thiosulphate oxidation, is overproduced under these growth conditions. Additionally, two electron carriers, cytochrome c551/c5 and HiPIP III, are also overproduced. Electron paramagnetic resonance spectroscopy suggested that these transporters participate in the reduction of the photosynthetic Reaction Centre. These results support the idea of a chemically and biologically formed thioarsenate being oxidized by the Sox system, with cytochrome c551/c5 and HiPIP III directing electrons towards the Reaction Centre.

Mechanism of acid and alkali electrolyzed water on the elimination of Listeria monocytogenes biofilm based on proteomic analysis

Acidic electrolyzed water is a relatively mature bactericide, which has a certain inhibitory effect on a variety of microorganisms, and is widely used in the field of food processing for cleaning, sterilization and disinfection. This study investigated the deactivation mechanisms of Listeria monocytogenes by Tandem Mass Tags quantitative proteomics analysis. Samples were treated through A1S4 (Alkaline electrolytic water treatment for 1 min and Acid electrolytic water treatment for 4 min), S3A1S1 (Acid electrolyzed water treatment 3 min, Alkaline electrolyzed water treatment 1 min and Acid electrolyzed water treatment 1 min), S5 (Acid electrolytic water treatment for 5 min). Proteomic analysis showed that the mechanism of acid alkaline electrolyzed water treatment to eliminate the inactivation of the biofilm of L. monocytogenes was related to protein transcription and extension, RNA processing and synthesis, gene regulation, sugar and amino acid transport and metabolism, signal transduction and ATP binding. The study on the influence mechanism and action mechanism of the combination of acidic and alkaline electrolyzed water to remove L. monocytogenes biofilm is helpful to understand the development of the process of removing biofilm by electrolyzed water, and provides theoretical support for the treatment of other microbial contamination problems in food processing by electrolyzed water.

Possible molecular basis of the biochemical effects of cysteine-derived persulfides

Persulfides (RSSH/RSS⁻) are species closely related to thiols (RSH/RS⁻) and hydrogen sulfide (H₂S/HS⁻), and can be formed in biological systems in both low and high molecular weight cysteine-containing compounds. They are key intermediates in catabolic and biosynthetic processes, and have been proposed to participate in the transduction of hydrogen sulfide effects. Persulfides are acidic, more acidic than thiols, and the persulfide anions are expected to be the predominant species at neutral pH. The persulfide anion has high nucleophilicity, due in part to the alpha effect, i.e., the increased reactivity of a nucleophile when the neighboring atom has high electron density. In addition, persulfides have electrophilic character, a property that is absent in both thiols and hydrogen sulfide. In this article, the biochemistry of persulfides is described, and the possible ways in which the formation of a persulfide could impact on the properties of the biomolecule involved are discussed.