Histamine poisoning is a significant public health and safety concern. Intoxication from ingestion of food containing high amounts of histamine may cause mild or severe symptoms that can even culminate in cardiac arrest. Nonetheless, although histamine levels in dairy products are not subject to any regulation, important outbreaks and severe adverse health effects have been reported due to intake of dairy products with a high histamine content, especially ripened cheeses. Histamine, a biogenic amine, can accumulate in dairy products as a result of the metabolism of starter and nonstarter lactic acid bacteria, as well as yeasts that contribute to the ripening or flavoring of the final product, or even as a result of spoilage bacteria. The aim of this review is to describe the microbiological causes of the presence of histamine in fermented milk products, and to propose control measures and potential methods for obtaining histamine‐free dairy products. Thus, this manuscript focuses on histamine‐producing microbiota in dairy products, highlighting the detection of histamine‐producing bacteria through traditional and novel techniques. In addition, this review aims to explore control measures to prevent the access of histamine‐producing microbiota to raw materials, as well as the formation of histamine in dairy products, such as a careful selection of starter cultures lacking the ability to produce histamine, or even the implementation of effective food processing technologies to reduce histamine‐producing microbiota. Finally, the removal of histamine already formed in dairy products through histamine‐degrading microorganisms or by enzymatic degradation will also be explored.
Cyanobacterial FurA works as a global regulator linking iron homeostasis to photosynthetic metabolism and the responses to different environmental stresses. Additionally, FurA modulates several genes involved in redox homeostasis and fulfills the characteristics of a heme-sensor protein whose interaction with this cofactor negatively affects its DNA binding ability. FurA from Anabaena PCC 7120 contains five cysteine residues, four of them arranged in two redox CXXC motifs. Aims: Our goals were to analyze in depth the putative contribution of these CXXC motifs in the redox properties of FurA and to identify potential interacting partners of this regulator. Results: Insulin reduction assays unravel that FurA exhibits disulfide reductase activity. Simultaneous presence of both CXXC signatures greatly enhances the reduction rate, although the redox motif containing Cys 101 and Cys 104 seems a major contributor to this activity. Disulfide reductase activity was not detected in other ferric uptake regulator (Fur) proteins isolated from heterotrophic bacteria. In vivo, FurA presents different redox states involving intramolecular disulfide bonds when is partially oxidized. Redox potential values for CXXC motifs, -235 and -238 mV, are consistent with those reported for other proteins displaying disulfide reductase activity. Pull-down and two-hybrid assays unveil potential FurA interacting partners, namely phosphoribulokinase Alr4123, the hypothetical amidase-containing domain All1140 and the DNA-binding protein HU. Innovation: A novel biochemical activity of cyanobacterial FurA based on its cysteine arrangements and the identification of novel interacting partners are reported. Conclusion: The present study discloses a putative connection of FurA with the cyanobacterial redox-signaling pathway.
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