Project description:The bacterium Geotalea uraniireducens, commonly found in uranium-contaminated environments, plays a key role in bioremediation strategies by converting the soluble hexavalent form of uranium (U(VI)) into less soluble forms (e.g., U(IV)). While most of the reduction and concomitant precipitation of uranium occur outside the cells, there have been reports of important reduction processes taking place in the periplasm. In any case, the triheme periplasmic cytochromes are key players, either by ensuring an effective interface between the cell's interior and exterior or by directly participating in the reduction of the metal. Therefore, understanding the functional mechanism of the highly abundant triheme cytochromes in G. uraniireducens' is crucial for elucidating the respiratory pathways in this bacterium. In this work, a detailed functional characterization of the triheme cytochromes PpcA and PpcB from G. uraniireducens was conducted using NMR and visible spectroscopy techniques. Despite sharing high amino acid sequence identity and structural homology with their counterparts from Geobacter sulfurreducens, the results showed that the heme reduction potential values are less negative, the order of oxidation of the hemes is distinct, and the redox and redox-Bohr network of interactions revealed unprecedented functional mechanisms in the cytochromes of G. uraniireducens. In these cytochromes, the reduction potential values of the three heme groups are much more similar, resulting in a narrower range of values, that facilitates directional electron flow from the inner membrane, thereby optimizing the uranium reduction.
Project description:Geobacteraceae transfer electrons from a donor such as acetate to an electron acceptor such as Fe(III) or U(VI). Geobacter uraniireducens is found in uranium-contaminated sites and plays an important role in in situ bioremediation. In this experiment, gene expression was compared between G. uraniireducens cultures grown in sediments from a uranium contaminated site amended with acetate and cultures grown in acetate/fumarate medium. Keywords: two-condition comparison
Project description:Previous analysis of gene transcript levels of Geobacter species in groundwater during in situ bioremediation of a uranium-contaminated aquifer detected expression of genes encoding superoxide dismutase (sodA) and cytochrome d ubiquinol oxidase (cydA), proteins known to be involved in the response to oxidative stress in other microorganisms. In order to further elucidate gene expression patterns that could be attributed to oxygen exposure, G. uraniumreducens was grown with acetate as the electron donor and fumarate as the electron acceptor in the presence of oxygen and compared to non-oxygen treated cultures.
Project description:This SuperSeries is composed of the following subset Series: GSE22497: Transcriptome analysis of Geobacter sulfurreducens under multiple growth conditions GSE22503: ChIP-chip of Geobacter sulfurreducens PCA with antibody against RNAP and RpoD under various conditions GSE22511: Genome-wide transcription start site determination of Geobacter sulfurreducens under multiple growth conditions Refer to individual Series
