[Project supported by FrenchBIC] The quest for the arsenic and selenium reductase(s) of Shewanella sp. O23S
Dr. Lucian Staicu, Institute of Microbiology, University of Warsaw (Poland), spent three months (September-November 2022) in the laboratory of Dr. Barbara Schoepp-Cothenet, Bioénergétique et Ingénierie des Protéines (BIP – UMR 7281), CNRS, Marseille. This research visit was financially supported by European Molecular Biology Organization (EMBO) and, partially, by FrenchBIC (Bioinorganic Chemistry).
The project explored the respiratory versatility of Shewanella sp. O23S (belonging to Shewanella baltica), isolated from a polymetallic environment (former gold mine in Złoty Stok, SW Poland). Shewanella sp. O23S is able to respire and reduce the oxyanions of selenium (Se), selenate (SeO42-) and selenite (SeO32-), yielding elemental Se biominerals (Se0) (Staicu et al., 2022). Interestingly, it also respires arsenate (AsO43-) to arsenite (AsO33-), as well as a variety of “common” electron acceptors such as nitrate (NO3–) and thiosulfate (S2O32-). For this study, we used a bioinformatic and a lab-based approach, aiming to identify the genes and the respiratory enzymes involved in these transformations. The bioinformatic analysis revealed that this strain does not use known genes for selenate and selenite respiration, potentially indicating a novel respiratory reductase/s. The experimental work explored the respiratory reductase(s) using gel electrophoresis and activity assays under anoxic conditions. The results showed multi substrate enzymes capable of reducing selenate, nitrate and arsenate, warranting a follow up study using transposon mutagenesis. Another significant result indicated that the strain O23S grows better on selenate than on arsenate, reflecting the higher Gibbs free energy provided by selenate (Staicu and Barton, 2021). The collaboration with Dr. Schoepp-Cothenet is ongoing.
I would like to sincerely thank FrenchBIC for this mobility grant, as well as EMBO for financial support. Equal acknowledgments go to Dr. Barbara Schoepp-Cothenet and to the BIP team for hosting me.
Dr. Lucian Staicu
References
Staicu LC, Barton LL (2021) Selenium respiration in anaerobic bacteria: does energy generation pay off? Journal of Inorganic Biochemistry 222, 111509 (link).
Staicu LC, Wójtowicz PJ, Molnár Z, Ruiz-Agudo E, Gallego JLR, Baragaño D, Pósfai M (2022) Interplay between arsenic and selenium biomineralization in Shewanella sp. O23S. Environmental Pollution 306, 119451 (link).