Recombinant<i>D. radiodurans</i>cells for bioremediation of heavy metals from acidic/neutral aqueous wastes

Misra, Chitra Seetharam; Appukuttan, Deepti; Kantamreddi, Venkata Siva Satyanarayana; Rao, A. T.; Apte, Shree Kumar

doi:10.4161/bbug.3.1.18878

Cited by 36 publications

(26 citation statements)

References 26 publications

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“…In recent years, our laboratory has explored the ability of phosphatase-expressing recombinant bacterial cells to bioprecipitate U and other heavy metals from solutions (29). The PhoN enzyme from Salmonella enterica serovar Typhimurium (encoded by the phoN gene, GenBank accession no.…”

Section: (Oh)]mentioning

confidence: 99%

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

Kulkarni

Misra

Gupta

et al. 2016

Appl Environ Microbiol

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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...

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Section: (Oh)]mentioning

confidence: 99%

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

Kulkarni

Misra

Gupta

et al. 2016

Appl Environ Microbiol

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“…27 Antibacterial activities of the synthesized AuNPs were assessed using the standard dilution micromethod and agar diffusion test. 25,27,31 For the standard dilution micromethod, 1 mL bacterial culture was exposed to 100 and 150 μg/mL of AuNPs, respectively. Phosphatebuffered saline replaced AuNPs in the control.…”

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confidence: 99%

“…24,25 Recently, the synthesis of silver nanoparticles and biotemplating of the preformed AuNPs into ordered arrays using S-layer protein lattices by D. radiodurans were investigated. 26,27 However, there are no reports available on the efficiency and reduction mechanism of direct AuNPs biosynthesis by D. radiodurans or evaluation of the bioactive functions of the AuNPs.…”

Section: Introductionmentioning

confidence: 99%

“…The reduction mechanism of D. radiodurans on noble metals has not been reported in previous studies. 25,26 The properties of AuNPs strongly depend on interactions between the nanoparticles and the adsorbed species on the surface of nanoparticles. 35 The reducing and capping factors for AuNPs present in D. radiodurans are still not fully known; however, we propose that the antioxidant compounds and related proteins in this bacterium may have provided reducing and stabilizing agents to convert Au(III) via Au(I) into AuNPs.…”

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“…31 It was found that the inhibition by AuNPs was more significant for Gram-negative E. coli than Gram-positive S. aureus, which was attributed to the differences in their cell wall compositions and growth rates. 25,52 The antibacterial property of AuNPs was also evaluated using the disk diffusion assay ( Figure 6B). The average diameter of the inhibition zone of AuNPs at 80 μg/disc was 9.21±0.20 mm for Gram-negative E. coli and was 8.95±0.17 mm for Gram-positive S. aureus.…”

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