Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

Yung, Mimi C.; Jiao, Yongqin

doi:10.1128/aem.01050-14

Cited by 43 publications

(45 citation statements)

References 48 publications

(62 reference statements)

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“…These include reductive precipitation by outer membrane cytochromes, conductive pili, or spores (6-10), 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).…”

Section: Importancementioning

confidence: 99%

“…The U biomineralization assay was conducted as previously described (4). Briefly, cells grown in PYE medium to late exponential phase were harvested, washed once with 10 mM NaCl, and resuspended in PIPES buffer to a final OD 600 of 0.5.…”

Section: Figmentioning

confidence: 99%

“…Uranyl nitrate was added to the suspensions to a final concentration of 100 M and incubated at RT for 30 min. The cell suspension was centrifuged at 20,000 ϫ g for 5 min, and the supernatant was collected and analyzed for U content using an Arsenazo III colorimetric assay as described previously (4,40). An abiotic control was also performed without addition of cells to control for abiotic U precipitation.…”

Section: Figmentioning

confidence: 99%

“…C. crescentus is known to tolerate high levels of U(VI) and is able to facilitate U biomineralization through the formation of uranium phosphate precipitates (4). Transcriptomic and proteomic studies during U exposure in C. crescentus revealed dozens of genes with significant changes in expression in response to U; these genes do not appear to overlap substantially with those that are variably expressed in response to other heavy metal stresses, such as cadmium (Cd) and chromium, suggesting a divergent cellular response to U(VI) (23,24).…”

mentioning

confidence: 99%

“…If we seek to task microbes with the cleanup of contaminated sites, an understanding of how microbes defend against U toxicity is crucial. Understanding these mechanisms is necessary for the optimization of strains intended for use as U biosensors (3) or for the purpose of bioremediation (2,4,5).…”

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

et al. 2015

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The ubiquitous aquatic bacterium Caulobacter crescentus is highly resistant to uranium (U) and facilitates U biomineralization and thus holds promise as an agent of U bioremediation. To gain an understanding of how C. crescentus tolerates U, we employed transposon (Tn) mutagenesis paired with deep sequencing (Tn-seq) in a global screen for genomic elements required for U resistance. Of the 3,879 annotated genes in the C. crescentus genome, 37 were found to be specifically associated with fitness under U stress, 15 of which were subsequently tested through mutational analysis. Systematic deletion analysis revealed that mutants lacking outer membrane transporters (rsaF a and rsaF b ), a stress-responsive transcription factor (cztR), or a ppGpp synthetase/hydrolase (spoT) exhibited a significantly lower survival rate under U stress. RsaF a and RsaF b , which are homologues of TolC in Escherichia coli, have previously been shown to mediate S-layer export. Transcriptional analysis revealed upregulation of rsaF a and rsaF b by 4-and 10-fold, respectively, in the presence of U. We additionally show that rsaF a mutants accumulated higher levels of U than the wild type, with no significant increase in oxidative stress levels. Our results suggest a function for RsaF a and RsaF b in U efflux and/or maintenance of membrane integrity during U stress. In addition, we present data implicating CztR and SpoT in resistance to U stress. Together, our findings reveal novel gene targets that are key to understanding the molecular mechanisms of U resistance in C. crescentus. IMPORTANCECaulobacter crescentus is an aerobic bacterium that is highly resistant to uranium (U) and has great potential to be used in U bioremediation, but its mechanisms of U resistance are poorly understood. We conducted a Tn-seq screen to identify genes specifically required for U resistance in C. crescentus. The genes that we identified have previously remained elusive using other omics approaches and thus provide significant insight into the mechanisms of U resistance by C. crescentus. In particular, we show that outer membrane transporters RsaF a and RsaF b , previously known as part of the S-layer export machinery, may confer U resistance by U efflux and/or by maintaining membrane integrity during U stress. U ranium (U) contamination is widespread and poses significant concerns for environmental ecology and human health (1). Chemical and physical techniques for waste treatment or removal of U are challenging and expensive. A promising, microbially mediated method for U remediation, in situ U immobilization, is more cost-effective and environmentally friendly than conventional approaches (2). If we seek to task microbes with the cleanup of contaminated sites, an understanding of how microbes defend against U toxicity is crucial. Understanding these mechanisms is necessary for the optimization of strains intended for use as U biosensors (3) or for the purpose of bioremediation (2, 4, 5).A great deal is known about various strategies used by microbes...

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Section: Importancementioning

confidence: 99%

Section: Figmentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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

et al. 2015

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Effect of natural uranium on the UMR-106 osteoblastic cell line: impairment of the autophagic process as an underlying mechanism of uranium toxicity

et al. 2016

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Natural uranium (U), which is present in our environment, exerts a chemical toxicity, particularly in bone where it accumulates. Generally, U is found at oxidation state +VI in its oxocationic form [Formula: see text] in aqueous media. Although U(VI) has been reported to induce cell death in osteoblasts, the cells in charge of bone formation, the molecular mechanism for U(VI) effects in these cells remains poorly understood. The objective of our study was to explore U(VI) effect at doses ranging from 5 to 600 µM, on mineralization and autophagy induction in the UMR-106 model osteoblastic cell line and to determine U(VI) speciation after cellular uptake. Our results indicate that U(VI) affects mineralization function, even at subtoxic concentrations (<100 µM). The combination of thermodynamic modeling of U with EXAFS data in the culture medium and in the cells clearly indicates the biotransformation of U(VI) carbonate species into a meta-autunite phase upon uptake by osteoblasts. We next assessed U(VI) effect at 100 and 300 µM on autophagy, a survival process triggered by various stresses such as metal exposure. We observed that U(VI) was able to rapidly activate autophagy but an inhibition of the autophagic flux was observed after 24 h. Thus, our results indicate that U(VI) perturbs osteoblastic functions by reducing mineralization capacity. Our study identifies for the first time U(VI) in the form of meta-autunite in mammalian cells. In addition, U(VI)-mediated inhibition of the autophagic flux may be one of the underlying mechanisms leading to the decreased mineralization and the toxicity observed in osteoblasts.

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Uranium bioprecipitation mediated by yeasts utilizing organic phosphorus substrates

Liang

Csetényi

Gadd

2016

Appl Microbiol Biotechnol

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Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

Cited by 43 publications

References 48 publications

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

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

Effect of natural uranium on the UMR-106 osteoblastic cell line: impairment of the autophagic process as an underlying mechanism of uranium toxicity

Uranium bioprecipitation mediated by yeasts utilizing organic phosphorus substrates

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