TY - JOUR

T1 - U mobilization and associated U isotope fractionation by sulfur-oxidizing bacteria

AU - Rosendahl, C. D.

AU - Roebbert, Y.

AU - Schippers, A.

AU - Weyer, S.

N1 - Funding Information: This work was funded by the DFG/SNSF grants (WE 2850-16/1 and 200021E-164209: Fate of tetravalent uranium under reducing conditions).

PY - 2023/7/18

Y1 - 2023/7/18

N2 - Uranium (U) contamination of the environment causes high risk to health, demanding for effective and sustainable remediation. Bioremediation via microbial reduction of soluble U(VI) is generating high fractions (>50%) of insoluble non-crystalline U(IV) which, however, might be remobilized by sulfur-oxidizing bacteria. In this study, the efficacy of Acidithiobacillus (At.) ferrooxidans and Thiobacillus (T.) denitrificans to mobilize non-crystalline U(IV) and associated U isotope fractionation were investigated. At. ferrooxidans mobilized between 74 and 91% U after 1 week, and U mobilization was observed for both, living and inactive cells. Contrary to previous observations, no mobilization by T. denitrificans could be observed. Uranium mobilization by At. ferrooxidans did not cause U isotope fractionation suggesting that U isotope ratio determination is unsuitable as a direct proxy for bacterial U remobilization. The similar mobilization capability of active and inactive At. ferrooxidans cells suggests that the mobilization is based on the reaction with the cell biomass. This study raises doubts about the long-term sustainability of in-situ bioremediation measures at U-contaminated sites, especially with regard to non-crystalline U(IV) being the main component of U bioremediation.

AB - Uranium (U) contamination of the environment causes high risk to health, demanding for effective and sustainable remediation. Bioremediation via microbial reduction of soluble U(VI) is generating high fractions (>50%) of insoluble non-crystalline U(IV) which, however, might be remobilized by sulfur-oxidizing bacteria. In this study, the efficacy of Acidithiobacillus (At.) ferrooxidans and Thiobacillus (T.) denitrificans to mobilize non-crystalline U(IV) and associated U isotope fractionation were investigated. At. ferrooxidans mobilized between 74 and 91% U after 1 week, and U mobilization was observed for both, living and inactive cells. Contrary to previous observations, no mobilization by T. denitrificans could be observed. Uranium mobilization by At. ferrooxidans did not cause U isotope fractionation suggesting that U isotope ratio determination is unsuitable as a direct proxy for bacterial U remobilization. The similar mobilization capability of active and inactive At. ferrooxidans cells suggests that the mobilization is based on the reaction with the cell biomass. This study raises doubts about the long-term sustainability of in-situ bioremediation measures at U-contaminated sites, especially with regard to non-crystalline U(IV) being the main component of U bioremediation.

KW - Acidithiobacillus ferrooxidans

KW - isotope fractionation

KW - laboratory batch experiments

KW - remobilization

KW - Thiobacillus denitrificans

KW - uranium

UR - http://www.scopus.com/inward/record.url?scp=85166437877&partnerID=8YFLogxK

U2 - 10.3389/fmicb.2023.1190962

DO - 10.3389/fmicb.2023.1190962

M3 - Article

AN - SCOPUS:85166437877

VL - 14

JO - Frontiers in microbiology

JF - Frontiers in microbiology

SN - 1664-302X

M1 - 1190962

ER -