Uptake and reduction of Se(IV) in two heterotrophic aerobic Pseudomonads strains isolated from boreal bog environment.

Merja Lusa, ,2 Vtt Technical Research Centre Of Finland, Espoo, Finland ,Malin Bomberg,Jenna Knuutinen

doi:10.3934/microbiol.2017.4.798

Merja Lusa, + Show 3 more

Open Access

https://doi.org/10.3934/microbiol.2017.4.798

Copy DOI

Abstract

Selenite (Se(IV), SeO32−) uptake and the effect of selenite supplement on protein synthesis was investigated in two Pseudomonas sp. strains isolated from a boreal bog. These aerobic bacteria efficiently reduced Se(IV) with intracellular reduced Se0 observed in the cytoplasm under dark aerobic conditions. The proteome analysis of Se(IV) supplement and temperature responses by SDS-PAGE gel electrophoresis showed variations in the protein expression on the 40–60 kDa regions following these stress factors, probably through enzymes associated to oxidative stress or temperature adaptation. NO3−/NO2−/SO42− addition enhanced Se(IV) uptake in both bacteria, but Se(IV) uptake sustained also under sulphur and nitrogen starvation. Our findings suggest two different transport mechanisms for Se(IV) uptake in these Pseudomonas sp. strains; a low affinity transport system up-regulated by NO3−/NO2−/SO42− and a distinct Se(IV)O32− regulated transport system. Following transport, Se(IV) is reduced in the cytoplasm, forming Se0 granules, visible in TEM and verified using EDX.

Highlights

IntroductionGlutathione and selenite spontaneously react to produce several selenium-containing compounds, including selenodiglutathione, glutathioselenol, hydrogen selenide and elemental selenium [12]
79Se is one of the high priority radionuclides in the long-term biosphere safety assessment of spent nuclear fuel [1]
Selenite (Se(IV), SeO32−) uptake and the effect of selenite supplement on protein synthesis was investigated in two Pseudomonas sp. strains isolated from a boreal bog

Summary

Introduction

Glutathione and selenite spontaneously react to produce several selenium-containing compounds, including selenodiglutathione, glutathioselenol, hydrogen selenide and elemental selenium [12] This reaction produces highly toxic oxygen species like H2O2 and O2− [13]. Some anaerobic and phototrophic aerobic selenium respiring bacteria have previously shown to be able to use selenium oxyanions as terminal electron acceptors precipitating insoluble elemental Se0 particles [11,18,19,20,21,22,23] Following reduction, both intracellular and extracellular selenium granules have been found in phylogenetically and physiologically distinct bacteria like Chromatium vinosum, Desulfovibrio desulfuricans, Sulfospirillum barnesii, Bacillus selenitireducens, Selenihalanaerobacter shriftii, Shewanella oneidensis MR-1, Paenibacillus selenitireducens sp. While Se-reduction has been shown to be an environmentally important process in diverse terrestrial and aquatic environments, the mechanisms of Se0 biomineralization are poorly understood and the molecular factors behind Se reduction reactions have not been identified [27]

Methods

Results

Discussion

Conclusion