Decrease of U(VI) Immobilization Capability of the Facultative Anaerobic Strain Paenibacillus sp. JG-TB8 under Anoxic Conditions Due to Strongly Reduced Phosphatase Activity

Abstract

Interactions of a facultative anaerobic bacterial isolate named Paenibacillus sp. JG-TB8 with U(VI) were studied under oxic and anoxic conditions in order to assess the influence of the oxygen-dependent cell metabolism on microbial uranium mobilization and immobilization. We demonstrated that aerobically and anaerobically grown cells of Paenibacillus sp. JG-TB8 accumulate uranium from aqueous solutions under acidic conditions (pH 2 to 6), under oxic and anoxic conditions. A combination of spectroscopic and microscopic methods revealed that the speciation of U(VI) associated with the cells of the strain depend on the pH as well as on the aeration conditions. At pH 2 and pH 3, uranium was exclusively bound by organic phosphate groups provided by cellular components, independently on the aeration conditions. At higher pH values, a part (pH 4.5) or the total amount (pH 6) of the dissolved uranium was precipitated under oxic conditions in a meta-autunite-like uranyl phosphate mineral phase without supplying an additional organic phosphate substrate. In contrast to that, under anoxic conditions no mineral formation was observed at pH 4.5 and pH 6, which was clearly assigned to decreased orthophosphate release by the cells. This in turn was caused by a suppression of the indigenous phosphatase activity of the strain. The results demonstrate that changes in the metabolism of facultative anaerobic microorganisms caused by the presence or absence of oxygen can decisively influence U(VI) biomineralization.

Combined use of flow cytometry and microscopy to study the interactions between the gram-negative betaproteobacterium Acidovorax facilis and uranium(VI)

“…JG-TB8, which was recovered from a soil sample of the uranium mining waste pile ''Haberland'' (Johanngeorgenstadt, Saxony, Germany), that displayed a uranium removal capacity of 138 mg U/g BDM (at pH 4.5) [35]. However, A. facilis, a bacterium not native to uranium-contaminated environments, was able to remove nearly the same amounts of uranium as those of the indigenous isolates.…”

Spectroscopic study on uranyl carboxylate complexes formed at the surface layer of Sulfolobus acidocaldarius

“…Recent studies suggested that uranyl, initial coordinated to these functional groups, can subsequently serve as nucleation sites for further uranium precipitation. 3,4 Therefore, a deeper knowledge on the complexation mechanisms at microbial surfaces is fundamental for understanding and modelling uranium behavior in the environment. In order to determine the structural key compounds for the complexation of U(VI), selected components of prokaryotic cell walls and membranes have been purified and their interactions with U(VI) have been investigated.…”

Transposon Mutagenesis Paired with Deep Sequencing of Caulobacter crescentus under Uranium Stress Reveals Genes Essential for Detoxification and Stress Tolerance

“…These include reductive precipitation by outer membrane cytochromes, conductive pili, or spores (6)(7)(8)(9)(10), surface adsorption by exopolysaccharide (EPS) or S-layers (9,11), or precipitation with phosphate (4,5,12,13). However, mechanisms used by cells for combating internal U toxicity are poorly understood (14).…”