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"Manganese"
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Consequences of Disturbing Manganese Homeostasis
Manganese (Mn) is an essential trace element with unique functions in the body; it acts as a cofactor for many enzymes involved in energy metabolism, the endogenous antioxidant enzyme systems, neurotransmitter production, and the regulation of reproductive hormones. However, overexposure to Mn is toxic, particularly to the central nervous system (CNS) due to it causing the progressive destruction of nerve cells. Exposure to manganese is widespread and occurs by inhalation, ingestion, or dermal contact. Associations have been observed between Mn accumulation and neurodegenerative diseases such as manganism, Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and amyotrophic lateral sclerosis. People with genetic diseases associated with a mutation in the gene associated with impaired Mn excretion, kidney disease, iron deficiency, or a vegetarian diet are at particular risk of excessive exposure to Mn. This review has collected data on the current knowledge of the source of Mn exposure, the experimental data supporting the dispersive accumulation of Mn in the brain, the controversies surrounding the reference values of biomarkers related to Mn status in different matrices, and the competitiveness of Mn with other metals, such as iron (Fe), magnesium (Mg), zinc (Zn), copper (Cu), lead (Pb), calcium (Ca). The disturbed homeostasis of Mn in the body has been connected with susceptibility to neurodegenerative diseases, fertility, and infectious diseases. The current evidence on the involvement of Mn in metabolic diseases, such as type 2 diabetes mellitus/insulin resistance, osteoporosis, obesity, atherosclerosis, and non-alcoholic fatty liver disease, was collected and discussed.
Journal Article
Manganese in Plants: From Acquisition to Subcellular Allocation
Manganese (Mn) is an important micronutrient for plant growth and development and sustains metabolic roles within different plant cell compartments. The metal is an essential cofactor for the oxygen-evolving complex (OEC) of the photosynthetic machinery, catalyzing the water-splitting reaction in photosystem II (PSII). Despite the importance of Mn for photosynthesis and other processes, the physiological relevance of Mn uptake and compartmentation in plants has been underrated. The subcellular Mn homeostasis to maintain compartmented Mn-dependent metabolic processes like glycosylation, ROS scavenging, and photosynthesis is mediated by a multitude of transport proteins from diverse gene families. However, Mn homeostasis may be disturbed under suboptimal or excessive Mn availability. Mn deficiency is a serious, widespread plant nutritional disorder in dry, well-aerated and calcareous soils, as well as in soils containing high amounts of organic matter, where bio-availability of Mn can decrease far below the level that is required for normal plant growth. By contrast, Mn toxicity occurs on poorly drained and acidic soils in which high amounts of Mn are rendered available. Consequently, plants have evolved mechanisms to tightly regulate Mn uptake, trafficking, and storage. This review provides a comprehensive overview, with a focus on recent advances, on the multiple functions of transporters involved in Mn homeostasis, as well as their regulatory mechanisms in the plant's response to different conditions of Mn availability.
Journal Article
Bacterial chemolithoautotrophy via manganese oxidation
Manganese is one of the most abundant elements on Earth. The oxidation of manganese has long been theorized
1
—yet has not been demonstrated
2
–
4
—to fuel the growth of chemolithoautotrophic microorganisms. Here we refine an enrichment culture that exhibits exponential growth dependent on Mn(II) oxidation to a co-culture of two microbial species. Oxidation required viable bacteria at permissive temperatures, which resulted in the generation of small nodules of manganese oxide with which the cells associated. The majority member of the culture—which we designate ‘
Candidatus
Manganitrophus noduliformans’—is affiliated to the phylum Nitrospirae (also known as Nitrospirota), but is distantly related to known species of
Nitrospira
and
Leptospirillum
. We isolated the minority member, a betaproteobacterium that does not oxidize Mn(II) alone, and designate it
Ramlibacter lithotrophicus
. Stable-isotope probing revealed
13
CO
2
fixation into cellular biomass that was dependent upon Mn(II) oxidation. Transcriptomic analysis revealed candidate pathways for coupling extracellular manganese oxidation to aerobic energy conservation and autotrophic CO
2
fixation. These findings expand the known diversity of inorganic metabolisms that support life, and complete a biogeochemical energy cycle for manganese
5
,
6
that may interface with other major global elemental cycles.
A co-culture of two newly identified microorganisms—‘
Candidatus
Manganitrophus noduliformans’ and
Ramlibacter lithotrophicus
—exhibits exponential growth that is dependent on manganese(II) oxidation, demonstrating the viability of this metabolism for supporting life.
Journal Article
Plain Language Summary on Scientific opinion on the tolerable upper intake level for manganese
This publication is linked to the following EFSA Journal article: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2023.8413.This publication is linked to the following EFSA Journal article: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2023.8413.
Journal Article
A bacterial isolate from the Black Sea oxidizes sulfide with manganese(IV) oxide
Mn is one of the most abundant redox-sensitive metals on earth. Some microorganisms are known to use Mn(IV) oxide (MnO₂) as electron acceptor for the oxidation of organic compounds or hydrogen (H₂), but so far the use of sulfide (H₂S) has been suggested but not proven. Here we report on a bacterial isolate which grows autotrophically and couples the reduction of MnO₂ to the oxidation of H₂S or thiosulfate (S2O3
2−) for energy generation. The isolate, originating from the Black Sea, is a species within the genus Sulfurimonas, which typically occurs with high cell numbers in the vicinity of sulfidic environments [Y. Han, M. Perner, Front. Microbiol. 6, 989 (2015)]. H₂S and S2O3
2− are oxidized completely to sulfate (SO4
2−) without the accumulation of intermediates. In the culture, Mn(IV) reduction proceeds via Mn(III) and finally precipitation of Ca-rich Mn(II) carbonate [Mn(Ca)CO₃]. In contrast to Mn-reducing bacteria, which use organic electron donors or H₂, Fe oxides are not observed to support growth, which may either indicate an incomplete gene set or a different pathway for extracellular electron transfer.
Journal Article