Impact of Tellurite on the Metabolism of Paenibacillus pabuli AL109b With Flagellin Production Explaining High Reduction Capacity

Identification of a multi-modal mechanism for Se(VI) reduction and Se(0) allotropic transition by Stenotrophomonas bentonitica

Microorganisms can play a key role in selenium (Se) bioremediation and the fabrication of Se-based nanomaterials by reducing toxic forms (Se(VI) and Se(IV)) into Se(0). In recent years, omics have become a useful tool in understanding the metabolic pathways involved in the reduction process. This paper aims to elucidate the specific molecular mechanisms involved in Se(VI) reduction by the bacterium Stenotrophomonas bentonitica. Both cytoplasmic and membrane fractions were able to reduce Se(VI) to Se(0) nanoparticles (NPs) with different morphologies (nanospheres and nanorods) and allotropes (amorphous, monoclinic, and trigonal). Proteomic analyses indicated an adaptive response against Se(VI) through the alteration of several metabolic pathways including those related to energy acquisition, synthesis of proteins and nucleic acids, and transport systems. Whilst the thioredoxin system and the Painter reactions were identified to play a crucial role in Se reduction, flagellin may also be involved in the allotropic transformation of Se. These findings suggest a multi-modal reduction mechanism is involved, providing new insights for developing novel strategies in bioremediation and nanoparticle synthesis for the recovery of critical materials within the concept of circular economy.

Microbial mechanisms to transform the super-trace element tellurium: a systematic review and discussion of nanoparticulate phases

Tellurium is a super-trace metalloid on Earth. Owing to its excellent physical and chemical properties, it is used in industries such as metallurgy and manufacturing, particularly of semiconductors and - more recently - solar panels. As the global demand for tellurium rises, environmental issues surrounding tellurium have recently aroused concern due to its high toxicity. The amount of tellurium released to the environment is increasing, and microorganisms play an important role in the biogeochemical cycling of environmental tellurium. This review focuses on novel developments on tellurium transformations driven by microbes and includes the following sections: (1) history and applications of tellurium; (2) toxicity of tellurium; (3) microbial detoxification mechanisms against soluble tellurium anions including uptake, efflux and methods of reduction, and reduced ability to cope with oxidation stress or repair damaged DNA; and (4) the characteristics and applications of tellurium nanoparticles (TeNPs) produced by microbes. This review raises the awareness of microorganisms in tellurium biogeochemical cycling and the growing applications for microbial tellurium nanoparticles.

Potential of tellurite resistance in heterotrophic bacteria from mining environments

Untreated mining wastes and improper disposal of high-tech devices generate an environmental increase of bioavailable metalloids, exerting stress on autochthonous microbial populations. Tellurium is a metalloid, an element with raising economic importance; nevertheless, its interaction with living organisms is not yet fully understood. Here we characterized aerobic heterotrophic bacteria, isolated from high metal-content mining residues, able to resist/reduce tellurite into tellurium structures and to determine the presence of confirmed tellurite resistance genetic determinants in resistant strains. We identified over 50 tellurite-resistant strains, among 144 isolates, eight strains reduced tellurite to tellurium at different rates, with the concomitant production of tellurium deposits. Most tellurite resistance genes were found in strains from Bacillales, with the prevalence of genes of the ter operon. This work demonstrated that bacterial isolates, from environments with a persistent selective pressure, are potential candidates for uncovering strategies for tellurite resistance and/or production of valuable Te-containing materials.

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Sites with continuous high metal pressure as a source of Te-resistant bacteria diversity

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Organism-specific Te (IV) reduction produces unique Te (0) insoluble structures

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Unveiled Te resistance genetic determinants and arrangements in Bacillales