Selenium in the environment

Cappelletti, Martina; Funari, Valerio; Gasparotto, Giorgio; Dinelli, Enrico; Zannoni, Davide

doi:10.2166/9781789061055_0003

Cited by 2 publications

(1 citation statement)

References 158 publications

(201 reference statements)

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“…1 ). The selenium oxyanions selenate [oxidation state +VI], selenite [+IV], and selenide [−II] can be converted into each other, passing elemental selenium [0], by biotic or abiotic reduction/oxidation ( 18 ). As selenium is toxic for many organisms already at low concentrations, the element can be detoxified by methylation leading to the volatile species methylselenol (MSe), DMSe, and dimethyldiselenide (DMDSe) ( 19 ) ( Fig.…”

Section: Introductionmentioning

confidence: 99%

Proteomic and transcriptomic analysis of selenium utilization in Methanococcus maripaludis

Funkner,

Poehlein,

Jehmlich

et al. 2024

mSystems

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Methanococcus maripaludis utilizes selenocysteine- (Sec-) containing proteins (selenoproteins), mostly active in the organism’s primary energy metabolism, methanogenesis. During selenium depletion, M. maripaludis employs a set of enzymes containing cysteine (Cys) instead of Sec. The genes coding for these Sec-/Cys-containing isoforms were the only genes known of which expression is influenced by the selenium status of the cell. Using proteomics and transcriptomics, approx. 7% and 12%, respectively, of all genes/proteins were found differentially expressed/synthesized in response to the selenium supply. Some of the genes identified involve methanogenesis, nitrogenase functions, and putative transporters. An increase of transcript abundance for putative transporters under selenium depletion indicated the organism’s effort to tap into alternative sources of selenium. M. maripaludis is known to utilize selenite and dimethylselenide as selenium sources. To expand this list, a selenium-responsive reporter strain was assessed with nine other, environmentally relevant selenium species. While the effect of some was very similar to that of selenite, others were effectively utilized at lower concentrations. Conversely, selenate and seleno - amino acids were only utilized at unphysiologically high concentrations and two compounds were not utilized at all. To address the role of the selenium-regulated putative transporters, M. maripaludis mutant strains lacking one or two of the putative transporters were tested for the capability to utilize the different selenium species. Of the five putative transporters analyzed by loss-of-function mutagenesis, none appeared to be absolutely required for utilizing any of the selenium species tested, indicating they have redundant and/or overlapping specificities or are not dedicated selenium transporters. IMPORTANCE While selenium metabolism in microorganisms has been studied intensively in the past, global gene expression approaches have not been employed so far. Furthermore, the use of different selenium sources, widely environmentally interconvertible via biotic and abiotic processes, was also not extensively studied before. Methanococcus maripaludis JJ is ideally suited for such analyses, thanks to its known selenium usage and available genetic tools. Thus, an overall view on the selenium regulon of M. maripaludis was obtained via transcriptomic and proteomic analyses, which inspired further experimentation. This led to demonstrating the use of selenium sources M. maripaludis was previously not known to employ. Also, an attempt—although so far unsuccessful—was made to pinpoint potential selenium transporter genes, in order to deepen our understanding of trace element utilization in this important model organism.

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Section: Introductionmentioning

confidence: 99%

Proteomic and transcriptomic analysis of selenium utilization in Methanococcus maripaludis

Funkner,

Poehlein,

Jehmlich

et al. 2024

mSystems

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Tellurite and Selenite: how can these two oxyanions be chemically different yet so similar in the way they are transformed to their metal forms by bacteria?

2022

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This opinion review explores the microbiology of tellurite, TeO32− and selenite, SeO32− oxyanions, two similar Group 16 chalcogen elements, but with slightly different physicochemical properties that lead to intriguing biological differences. Selenium, Se, is a required trace element compared to tellurium, Te, which is not. Here, the challenges around understanding the uptake transport mechanisms of these anions, as reflected in the model organisms used by different groups, are described. This leads to a discussion around how these oxyanions are subsequently reduced to nanomaterials, which mechanistically, has controversies between ideas around the molecule chemistry, chemical reactions involving reduced glutathione and reactive oxygen species (ROS) production along with the bioenergetics at the membrane versus the cytoplasm. Of particular interest is the linkage of glutathione and thioredoxin chemistry from the cytoplasm through the membrane electron transport chain (ETC) system/quinones to the periplasm. Throughout the opinion review we identify open and unanswered questions about the microbial physiology under selenite and tellurite exposure. Thus, demonstrating how far we have come, yet the exciting research directions that are still possible. The review is written in a conversational manner from three long-term researchers in the field, through which to play homage to the late Professor Claudio Vásquez.

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Selenium in the environment

Cited by 2 publications

References 158 publications

Proteomic and transcriptomic analysis of selenium utilization in Methanococcus maripaludis

Proteomic and transcriptomic analysis of selenium utilization in Methanococcus maripaludis

Tellurite and Selenite: how can these two oxyanions be chemically different yet so similar in the way they are transformed to their metal forms by bacteria?

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