Uranium sequestration by a marine cyanobacterium, Synechococcus elongatus strain BDU/75042

Acharya, Celin; Joseph, D. Paul; Apte, Shree Kumar

doi:10.1016/j.biortech.2008.10.047

Cited by 85 publications

(48 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To simulate a carbonatedominated geochemical condition, a stock solution composed predominantly of uranyl carbonate complexes was prepared by the addition of a 1/10th volume of saturated ammonium carbonate to a 100 mM uranyl nitrate hexahydrate stock solution (final U concentration, 89 mM; carbonate concentration, 214 mM) (32,35,36). The formation of carbonate complexes with U was verified by monitoring the absorption spectra of solution in the visible light range between 400 and 500 nm (UV Unicam 300; Thermo Scientific) with specific peaks at 434 nm, 448 nm, and 464 nm (35,36 ammonium carbonate, as explained above; final pH, 9.0). The concentration of carbonate in GC2 in all assays was always 2.4-fold higher than the U concentration used; i.e., the carbonate-to-U ratio of 2.4 was always maintained.…”

Section: Methodsmentioning

confidence: 99%

Interaction of Uranium with Bacterial Cell Surfaces: Inferences from Phosphatase-Mediated Uranium Precipitation

Kulkarni

Misra

Gupta

et al. 2016

Appl Environ Microbiol

View full text Add to dashboard Cite

Deinococcus radiodurans and Escherichia coli expressing either PhoN, a periplasmic acid phosphatase, or PhoK, an extracellular alkaline phosphatase, were evaluated for uranium (U) bioprecipitation under two specific geochemical conditions (GCs): (i) a carbonate-deficient condition at near-neutral pH (GC1), and (ii) a carbonate-abundant condition at alkaline pH (GC2). Transmission electron microscopy revealed that recombinant cells expressing PhoN/PhoK formed cell-associated uranyl phosphate precipitate under GC1, whereas the same cells displayed extracellular precipitation under GC2. These results implied that the cell-bound or extracellular location of the precipitate was governed by the uranyl species prevalent at that particular GC, rather than the location of phosphatase. MINTEQ modeling predicted the formation of predominantly positively charged uranium hydroxide ions under GC1 and negatively charged uranyl carbonate-hydroxide complexes under GC2. Both microbes adsorbed 6-to 10-fold more U under GC1 than under GC2, suggesting that higher biosorption of U to the bacterial cell surface under GC1 may lead to cell-associated U precipitation. In contrast, at alkaline pH and in the presence of excess carbonate under GC2, poor biosorption of negatively charged uranyl carbonate complexes on the cell surface might have resulted in extracellular precipitation. The toxicity of U observed under GC1 being higher than that under GC2 could also be attributed to the preferential adsorption of U on cell surfaces under GC1. This work provides a vivid description of the interaction of U complexes with bacterial cells. The findings have implications for the toxicity of various U species and for developing biological aqueous effluent waste treatment strategies. IMPORTANCEThe present study provides illustrative insights into the interaction of uranium (U) complexes with recombinant bacterial cells overexpressing phosphatases. This work demonstrates the effects of aqueous speciation of U on the biosorption of U and the localization pattern of uranyl phosphate precipitated as a result of phosphatase action. Transmission electron microscopy revealed that location of uranyl phosphate (cell associated or extracellular) was primarily influenced by aqueous uranyl species present under the given geochemical conditions. The data would be useful for understanding the toxicity of U under different geochemical conditions. Since cell-associated precipitation of metal facilitates easy downstream processing by simple gravitybased settling down of metal-loaded cells, compared to cumbersome separation techniques, the results from this study are of considerable relevance to effluent treatment using such cells. Bioremediation strategies, such as bioreduction (1-3), biosorption (4-8), bioaccumulation (9, 10), and bioprecipitation (5, 11, 12, 13), have been studied for their potential to immobilize U from solutions. There is also a large body of work on microbial interactions with uranium relevant to environmental in situ bioremediation. The...

show abstract

Section: Methodsmentioning

confidence: 99%

Interaction of Uranium with Bacterial Cell Surfaces: Inferences from Phosphatase-Mediated Uranium Precipitation

Kulkarni

Misra

Gupta

et al. 2016

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…For instance, Alvarado Quiroz et al (2006) have reported the strong binding capacity of sticky EPS-derived acid polysaccharide compounds for thorium (IV). Likewise, Acharya et al (2009) showed that the ability of Synechococcus elongatus to bind uranium was due to its complexation with ligands within the EPS coating cell surface. Extracellular polymeric substances are known to stabilise microbial cells against highenergy environments and to provide a chemically protective microenvironment.…”

Section: Micro-environmentmentioning

confidence: 99%

Preliminary investigations on picoplankton-related precipitation of alkaline-earth metal carbonates in meso-oligotrophic lake Geneva (Switzerland)

Jaquet¹,

Nirel

Martignier

2013

J Limnol

View full text Add to dashboard Cite

In the course of a routine water-quality survey in meso-oligotrophic lake Geneva (Switzerland), suspended matter was collected by filtration on 0.2 μm membranes in July and August 2012 at the depth of maximal chlorophyll a (Chl a) concentration (2 mg m^–3). Examination by scanning electron microscopy revealed the presence of numerous dark and gelatinous patches occluding the pores of the membranes, containing high numbers of picoplanktonic cells and, in places, clusters of high-reflectance smooth microspheres (1-2 μm in diameter). Their chemical composition, determined by semi-quantitative, energy-dispersive X ray spectroscopy (EDS) showed magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Ba) (alkaline earth metals) to be the dominant cations. Among the anions, phosphorus (P) and carbon (C) were present, but only the latter is considered here (as carbonate). The microspheres were subdivided into four types represented in a Ca-Sr-Ba ternary space. All types are confined within a domain bound by Ca>45, Sr<10 and Ba<50 (in mole %). Type I, the most frequent, displays a broad variability in Ba/Ca, even within a given cluster. Types II and III are devoid of Ba, but may incorporate P. Type IV contains only Ca. The Type I composition resembles that of benstonite, a Group IIA carbonate that was recently found as intracellular granules in a cyanobacterium from alkaline lake Alchichica (Mexico).Lake Geneva microspheres are solid, featureless and embedded in a mucilage-looking substance in the vicinity of, but seemingly not inside, picoplanktonic cells morphologically similar to Chlorella and Synechococcus. In summer 2012, the macroscopic physico-chemical conditions in lake Geneva epilimnion were such as to allow precipitation of Ca but not of Sr and Ba carbonates. Favourable conditions did exist, though, in the micro-environment provided by the combination of active picoplankton and a mucilaginous envelope. Further studies are ongoing to investigate the vertical distribution of the microspheres, their internal structure and their exact mineralogical composition, as well as the taxonomy of the picoplankton and the nature of the mucilage, in order to gain a proper understanding of this intriguing process of alkaline-earth metals sequestration.

show abstract

“…The cell pellets were dried at 60°C, ground to homogeneity, and analyzed by X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy to determine the oxidation state and the neighboring atoms of the complexed uranium, respectively. A solution of 10 Ϫ3 M [UO 2 (CO 3 ) 2 ] 2Ϫ served as the reference sample for the oxidation state of uranium, i.e., U(VI) confirmed previously with UV-Vis spectroscopy (72).…”

Section: Methodsmentioning

confidence: 56%

“…The filamentous, heterocystous, nitrogen-fixing, photoautotrophic, marine brackish water cyanobacterium, Anabaena torulosa was grown in combined nitrogenfree BG-11 media (69) (71,72). Each assay comprised 10 ml of nitrogen-supplemented BG-11 (P Ϫ ) medium with or without 100 M uranyl carbonate [UO 2 (CO 3 ) 2 ] 2Ϫ at pH 7.8.…”

Section: Methodsmentioning

confidence: 99%

Unusual Versatility of the Filamentous, Diazotrophic Cyanobacterium Anabaena torulosa Revealed for Its Survival during Prolonged Uranium Exposure

Acharya

Chandwadkar

Nayak

2017

Appl Environ Microbiol

View full text Add to dashboard Cite

Reports on interactions between cyanobacteria and uranyl carbonate are rare. Here, we present an interesting succession of the metabolic responses employed by a marine, filamentous, diazotrophic cyanobacterium, Anabaena torulosa for its survival following prolonged exposure to uranyl carbonate extending up to 384 h at pH 7.8 under phosphate-limited conditions. The cells sequestered uranium (U) within polyphosphates on initial exposure to 100 M uranyl carbonate for 24 to 28 h. Further incubation until 120 h resulted in (i) significant degradation of cellular polyphosphates causing extensive chlorosis and cell lysis, (ii) akinete differentiation followed by (iii) extracellular uranyl precipitation. X-ray diffraction (XRD) analysis, fluorescence spectroscopy, X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) spectroscopy established the identity of the bioprecipitated uranium as a U(VI) autunite-type mineral, which settled at the bottom of the vessel. Surprisingly, A. torulosa cells resurfaced as small green flakes typical of actively growing colonies on top of the test solutions within 192 to 240 h of U exposure. A consolidated investigation using kinetics, microscopy, and physiological and biochemical analyses suggested a role of inducible alkaline phosphatase activity of cell aggregates/akinetes in facilitating the germination of akinetes leading to substantial regeneration of A. torulosa by 384 h of uranyl incubation. The biomineralized uranium appeared to be stable following cell regeneration. Altogether, our results reveal novel insights into the survival mechanism adopted by A. torulosa to resist sustained uranium toxicity under phosphate-limited oxic conditions. IMPORTANCE Long-term effects of uranyl exposure in cyanobacteria under oxic phosphate-limited conditions have been inadequately explored. We conducted a comprehensive examination of the metabolic responses displayed by a marine cyanobacterium, Anabaena torulosa, to cope with prolonged exposure to uranyl carbonate at pH 7.8 under phosphate limitation. Our results highlight distinct adaptive mechanisms harbored by this cyanobacterium that enabled its natural regeneration following extensive cell lysis and uranium biomineralization under sustained uranium exposure. Such complex interactions between environmental microbes such as Anabaena torulosa and uranium over a broader time range advance our understanding on the impact of microbial processes on uranium biogeochemistry.KEYWORDS biomineralization, cyanobacteria, phosphatase, polyphosphates, regeneration, uranium M icroorganisms have existed on earth for at least 3.5 billion years (1) and are the most successful life forms to date (2). They have been exposed to their immediate environments comprising essential elements or complex mixtures of naturally occur-

show abstract

Uranium sequestration by a marine cyanobacterium, Synechococcus elongatus strain BDU/75042

Cited by 85 publications

References 31 publications

Interaction of Uranium with Bacterial Cell Surfaces: Inferences from Phosphatase-Mediated Uranium Precipitation

Interaction of Uranium with Bacterial Cell Surfaces: Inferences from Phosphatase-Mediated Uranium Precipitation

Preliminary investigations on picoplankton-related precipitation of alkaline-earth metal carbonates in meso-oligotrophic lake Geneva (Switzerland)

Unusual Versatility of the Filamentous, Diazotrophic Cyanobacterium Anabaena torulosa Revealed for Its Survival during Prolonged Uranium Exposure

Contact Info

Product

Resources

About