Publications by authors named "Shang Dai"

16 Publications

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Astaxanthin and its gold nanoparticles mitigate cadmium toxicity in rice by inhibiting cadmium translocation and uptake.

Sci Total Environ 2021 Sep 3;786:147496. Epub 2021 May 3.

National Key Laboratory of Rice Biology, Institute of Crop Sciences, Zhejiang University, Hangzhou, China. Electronic address:

Cadmium (Cd) is one of the main heavy metal in rice, Cd uptake by cereal crops from soil leads to toxicity in plants and pose serious health risks due to human body's accumulation through the food chain. Astaxanthin, a natural and anti-oxidative oxycarotenoid, is widely distributed in various microorganisms and seafood. In this study, we demonstrated that astaxanthin in the form of gold nanoparticles (Ast-AuNPs) can efficiently alleviate Cd toxicity to a greater extent in hydroponically grown rice plants than single astaxanthin. When supplemented with 100 μg/mL Ast-AuNPs in medium, the Cd level of rice was significantly reduced by 26.2% (in roots) and 85.9% (in leaves), respectively. We also found Ast-AuNPs supplement restores chlorophyll biosynthesis and mitigate Cd-induced oxidative stresses: the contents of superoxide anion (O), hydrogen peroxide (HO), and malondialdehyde (MDA) were significantly reduced while the activity of the antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) was significantly elevated. Further study showed that the supplement of Ast-AuNPs inhibited Cd-induced gene expression of the metal transporter genes (OsHMA2, OsHMA3, OsIRT1, OsIRT2, OsNramp1, and OsNramp5) in rice roots. Moreover, Ast-AuNPs regulated the metabolism of free amino acids and increased the level of non-enzymatic antioxidants such as glutathione and ascorbic acid. Therefore, this study demonstrates that Ast-AuNPs could mitigate the Cd toxicity in rice seedlings by suppressing Cd uptake, scavenging of ROS, and enhancing the activity of antioxidants, and also expands the application of functional gold nanoparticles in the alleviation of heavy metal pollution in plants.
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http://dx.doi.org/10.1016/j.scitotenv.2021.147496DOI Listing
September 2021

Colonized extremophile Deinococcus radiodurans alleviates toxicity of cadmium and lead by suppressing heavy metal accumulation and improving antioxidant system in rice.

Environ Pollut 2021 Apr 18;284:117127. Epub 2021 Apr 18.

MOE Key Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, Hangzhou, China; Key Laboratory for Green Processing of Chemical Engineering of Xinjiang Bingtuan, School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, China. Electronic address:

Cadmium (Cd) and lead (Pb) are the major toxic heavy metals accumulated in rice and pose a serious threat to human health. The most important remediation strategy is to reduce the translocation of these heavy metals from polluted soil to rice. Bioremediation using microorganisms had been widely used for preventing environmental heavy metal pollution, and the interaction between microorganisms and plants is critical to reduce the heavy metal stress. In this study, we demonstrated that an extremophile Deinococcus radiodurans, especially its mutant strain-Δdr2577 which is deficient in cell surface-layer, could efficiently prevent the translocation and damages of Cd or Pb in rice. The bacterial cells efficiently removed Cd or Pb from culture medium. Following colonization of Δdr2577 cells in rice root, Cd level decreased to 71.6% in root and 60.9% in shoot, comparing to the plants treated with Cd alone; Pb level decreased to 73.3% in root and 56.9% in shoot, comparing to the plants treated with Pb alone. Meanwhile, the bacterial cells released their intracellular antioxidant-related molecules including glutamate and manganese ions into culture medium. Accumulation of glutamate and manganese ions detected in rice root and shoot ameliorate Cd/Pb-induced oxidative stress as indicated by reduced levels of ROS and enhanced activities of antioxidant enzymes in rice. Our results provide a potential application of an extremophile bacterium in alleviating heavy metal toxicity in rice. The main findings of the work reveal the interaction between the D. radiodurans and rice, as well as the alleviating mechanism of Cd and Pb toxicity through suppressing heavy metal accumulation and improving the antioxidant system in rice by the extremophile bacterium.
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http://dx.doi.org/10.1016/j.envpol.2021.117127DOI Listing
April 2021

Dynamic Polyphosphate Metabolism Coordinating with Manganese Ions Defends against Oxidative Stress in the Extreme Bacterium Deinococcus radiodurans.

Appl Environ Microbiol 2021 03 11;87(7). Epub 2021 Mar 11.

MOE Key Laboratory of Biosystems Homeostasis & Protection, College of Life Sciences, Zhejiang University, Hangzhou, China

is an extreme bacterium with unparalleled resistance to oxidative stresses. Accumulation of intracellular Mn complexing with small metabolites is the key contributor to the tolerance of against oxidative stress. However, the intracellular reservoir of Mn ions and homeostatic regulation of the Mn complex in remain unclear. We identified an evolutionarily ancient and negatively charged phosphate polymer (polyphosphate [PolyP]) in We investigated PolyP metabolism in the response of to oxidative stress. The genes , encoding polyphosphatase kinase (PPK; the subscript "" refers to ), and , encoding exopolyphosphatase (PPX), were identified. PPX is a novel exopolyphosphatase with a cofactor preference to Mn, which enhances the dimerization and activity of PPX to allow the effective cleavage of PolyP-Mn. PPK and PPX exhibited different dynamic expression profiles under oxidative stress. First, was upregulated leading to the accumulation of PolyP, which chelated large amounts of intracellular Mn ions. Subsequently, the expression level of decreased while was substantially upregulated and effectively hydrolyzed inactive PolyP-Mn to release phosphate (Pi) and Mn, which could form into Mn-Pi complexes to scavenge O and protect proteins from oxidative damage. Hence, dynamic cellular PolyP metabolites complexed with free Mn ions highlight a defense strategy of in response to oxidative stress. The Mn-phosphate complex (Mn-Pi) plays a key role in the cellular resistance of radioresistant bacteria. The evolutionarily ancient polyphosphate polymers (polyphosphate [PolyP]) could effectively chelate Mn and donate phosphates. However, the intracellular reservoir of Mn ions and homeostatic regulation of the Mn-Pi complex remain unclear. Here, we investigated the relationship of PolyP metabolites and Mn homeostasis and how they function to defend against oxidative stress in the radioresistant bacterium We found that PPX (the subscript "" refers to ) is a novel exopolyphosphatase with a cofactor preference for Mn, mediating PolyP-Mn degradation into Pi and Mn ions. The formed Mn-Pi complexes effectively protect proteins. The dynamic PolyP metabolism coordinating with Mn ions is a defense strategy of in response to oxidative stress. The findings not only provide new insights into the resistance mechanism of the extreme bacterium but also broaden our understanding of the functions of PolyP metabolism in organisms.
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http://dx.doi.org/10.1128/AEM.02785-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8091604PMC
March 2021

Late embryogenesis abundant group3 protein (DrLEA3) is involved in antioxidation in the extremophilic bacterium Deinococcus radiodurans.

Microbiol Res 2020 Nov 22;240:126559. Epub 2020 Jul 22.

Institute of Biophysics, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China; MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang University, Hangzhou, Zhejiang, China. Electronic address:

Deinococcus radiodurans is able to survive under extreme conditions, including high doses of ionizing radiation, desiccation and oxidative stress. In addition to enhanced DNA repair capabilities, an effective antioxidation system plays an important role in its robustness. Previous studies have linked the radiation resistance of D. radiodurans to its prolonged desiccation tolerance phenotype, which both cause DNA damage. In the current study, we investigated the roles of dr_1172 in D. radiodurans, the gene encoding a typical group 3 LEA protein (DrLEA3) conserved within Deinococcus species. In addition to the increased transcriptional level under oxidative stress, the inactivation of dr_1172-sensitized cells to HO treatments and the reduced cellular antioxidation activities suggested that dr_1172 is involved in the cellular defense against oxidative stress. Moreover, DrLEA3 was enriched at the cell membrane and bound to various types of metal ions. Cells devoid of DrLEA3 showed a decreased intracellular Mn/Fe concentration ratio, indicating that DrLEA3 also plays a role in maintaining metal ion homeostasis in vivo.
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http://dx.doi.org/10.1016/j.micres.2020.126559DOI Listing
November 2020

Functionalized Gold and Silver Bimetallic Nanoparticles Using Protein Extract Mediate Degradation of Toxic Dye Malachite Green.

Int J Nanomedicine 2020 16;15:1823-1835. Epub 2020 Mar 16.

MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang University, Hangzhou, People's Republic of China.

Background: Biodegradation of toxic organic dye using nanomaterial-based microbial biocatalyst is an ecofriendly and promising technique.

Materials And Methods: Here, we have investigated the novel properties of functionalized Au-Ag bimetallic nanoparticles using extremophilic proteins (Drp-Au-AgNPs) and their degradation efficiency on the toxic triphenylmethane dye malachite green (MG).

Results And Discussion: The prepared Drp-Au-AgNPs with an average particle size of 149.8 nm were capped by proteins through groups including hydroxyl and amide. Drp-Au-AgNPs demonstrated greater degradation ability (83.68%) of MG than cells and monometallic AuNPs. The major degradation product was identified as 4-(dimethylamino) benzophenone, which is less toxic than MG. The degradation of MG was mainly attributed to the capping proteins on Drp-Au-AgNPs. The bimetallic NPs could be reused and maintained MG degradation ability (>64%) after 2 cycles.

Conclusion: These results suggest that the easily prepared Drp-Au-AgNPs have potential applications as novel nanomedicine for MG detoxification, and nanomaterial for biotreatment of a toxic polyphenyl dye-containing wastewater.
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http://dx.doi.org/10.2147/IJN.S236683DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7083632PMC
July 2020

-Cytosine DNA Methylation Is Involved in the Maintenance of Genomic Stability in .

Front Microbiol 2019 21;10:1905. Epub 2019 Aug 21.

The MOE Key Laboratory of Biosystems Homeostasis & Protection, Zhejiang University, Hangzhou, China.

DNA methylation serves as a vital component of restriction-modification (R-M) systems in bacteria, where it plays a crucial role in defense against foreign DNA. Recent studies revealed that DNA methylation has a global impact on gene expression. , an ideal model organism for studying DNA repair and genomic stability, possesses unparalleled resistance to DNA-damaging agents such as irradiation and strong oxidation. However, details on the methylome of this bacterium remain unclear. Here, we demonstrate that -cytosine is the major methylated form (4mC) in . A novel methylated motif, "CCGCGG" was identified that was fully attributed to M.DraR1 methyltransferase. M.DraR1 can specifically bind and methylate the second cytosine at atom of "CCGCGG" motif, preventing its digestion by a cognate restriction endonuclease. Cells deficient in 4mC modification displayed higher spontaneous rifampin mutation frequency and enhanced DNA recombination and transformation efficiency. And genes involved in the maintenance of genomic stability were differentially expressed in conjunction with the loss of M.DraR1. This study provides evidence that -cytosine DNA methylation contributes to genomic stability of and lays the foundation for further research on the mechanisms of epigenetic regulation by R-M systems in bacteria.
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http://dx.doi.org/10.3389/fmicb.2019.01905DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6712171PMC
August 2019

Gold Nanoparticles Biosynthesized and Functionalized Using a Hydroxylated Tetraterpenoid Trigger Gene Expression Changes and Apoptosis in Cancer Cells.

ACS Appl Mater Interfaces 2018 Oct 17;10(43):37353-37363. Epub 2018 Oct 17.

Key Laboratory for Nuclear-Agricultural Sciences of Chinese Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences , Zhejiang University , No. 268, Kaixuan Road , Hangzhou 310029 , China.

Understanding the synthetic mechanisms and cell-nanoparticle interactions of biosynthesized and functionalized gold nanoparticles (AuNPs) using natural products is of great importance for developing their applications in nanomedicine. In this study, we detailed the biotransformation mechanism of Au(III) into AuNPs using a hydroxylated tetraterpenoid deinoxanthin (DX) from the extremophile Deinococcus radiodurans. During the process, Au(III) was rapidly reduced to Au(I) and subsequently reduced to Au(0) by deprotonation of the hydroxyl head groups of the tetraterpenoid. The oxidized form, deprotonated 2-ketodeinoxanthin (DX3), served as a surface-capping agent to stabilize the AuNPs. The functionalized DX-AuNPs demonstrated stronger inhibitory activity against cancer cells compared with sodium citrate-AuNPs and were nontoxic to normal cells. DX-AuNPs accumulated in the cytoplasm, organelles, and nuclei, and induced reactive oxygen species generation, DNA damage, and apoptosis within MCF-7 cancer cells. In the cells treated with DX-AuNPs, 374 genes, including RRAGC gene, were upregulated; 135 genes, including the genes encoding FOXM1 and NR4A1, were downregulated. These genes are mostly involved in metabolism, cell growth, DNA damage, oxidative stress, autophagy, and apoptosis. The anticancer activity of the DX-AuNPs was attributed to the alteration of gene expression and induction of apoptosis. Our results provide significant insight into the synthesis mechanism of AuNPs functionalized with natural tetraterpenoids, which possess enhanced anticancer potential.
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http://dx.doi.org/10.1021/acsami.8b09206DOI Listing
October 2018

DR1440 is a potential iron efflux protein involved in maintenance of iron homeostasis and resistance of Deinococcus radiodurans to oxidative stress.

PLoS One 2018 14;13(8):e0202287. Epub 2018 Aug 14.

Key Laboratory for Nuclear-Agricultural Sciences of Chinese Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China.

Iron acquisition by bacteria is well studied, but iron export from bacteria is less understood. Herein, we identified dr1440 with a P-type ATPase motif as a potential exporter of iron from Deinococcus radiodurans, a bacterium known for its extreme resistance to radiation and oxidants. The DR1440 was located in cell membrane as demonstrated by fluorescence labelling analysis. Mutation of dr1440 resulted in cellular accumulation of iron ions, and expression level of dr1440 was up-regulated significantly under iron ion or hydrogen peroxide stress in the wild-type strain, implicating DR1440 as a potential iron efflux protein. The dr1440 mutant displayed higher sensitivity to iron ions and oxidative stresses including hydrogen peroxide, hypochlorous acid, and gamma-ray irradiation compared with the wild-type strain. The high amount of iron in the mutant strain resulted in severe protein carbonylation, suggesting that DR1440 might contribute to intracellular protein protection against reactive oxygen species (ROS) generated from ferrous ion-mediated Fenton-reaction. Mutations of S297A and C299A led to intracellular accumulation of iron, indicating that S297 and C299 might be important functional residues of DR1440. Thus, DR1440 is a potential iron efflux protein involved in iron homeostasis and oxidative stress-resistance of D. radiodurans.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0202287PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6091924PMC
February 2019

Biosynthesis of Au, Ag and Au-Ag bimetallic nanoparticles using protein extracts of and evaluation of their cytotoxicity.

Int J Nanomedicine 2018 9;13:1411-1424. Epub 2018 Mar 9.

Key Laboratory for Nuclear-Agricultural Sciences of Chinese Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, People's Republic of China.

Background: Biosynthesis of noble metallic nanoparticles (NPs) has attracted significant interest due to their environmental friendly and biocompatible properties.

Methods: In this study, we investigated syntheses of Au, Ag and Au-Ag bimetallic NPs using protein extracts of , which demonstrated powerful metal-reducing ability. The obtained NPs were characterized and analyzed by various spectroscopy techniques.

Results: The protein extract-mediated silver nanoparticles (Drp-AgNPs) were preferably monodispersed and stably distributed compared to protein extract-mediated gold nanoparticles (Drp-AuNPs). Drp-AgNPs and Drp-AuNPs exhibited spherical morphology with average sizes of 37.13±5.97 nm and 51.72±7.38 nm and zeta potential values of -18.31±1.39 mV and -15.17±1.24 mV at pH 7, respectively. The release efficiencies of Drp-AuNPs and Drp-AgNPs measured at 24 h were 3.99% and 18.20%, respectively. During the synthesis process, Au(III) was reduced to Au(I) and further to Au(0) and Ag(I) was reduced to Ag(0) by interactions with the hydroxyl, amine, carboxyl, phospho or sulfhydryl groups of proteins and subsequently stabilized by these groups. Some characteristics of Drp-AuNPs were different from those of Drp-AgNPs, which could be attributed to the interaction of the NPs with different binding groups of proteins. The Drp-AgNPs could be further formed into Au-Ag bimetallic NPs via galvanic replacement reaction. Drp-AuNPs and Au-Ag bimetallic NPs showed low cytotoxicity against MCF-10A cells due to the lower level of intracellular reactive oxygen species (ROS) generation than that of Drp-AgNPs.

Conclusions: These results are crucial to understand the biosynthetic mechanism and properties of noble metallic NPs using the protein extracts of bacteria. The biocompatible Au or Au-Ag bimetallic NPs are applicable in biosensing, bioimaging and biomedicine.
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http://dx.doi.org/10.2147/IJN.S149079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5849937PMC
May 2018

Toxin-Antitoxin MazEF-dr Mediates Cell Death in Response to DNA Damage Stress.

Front Microbiol 2017 26;8:1427. Epub 2017 Jul 26.

Key Laboratory of Nuclear Agricultural Science of Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences, Zhejiang UniversityHangzhou, China.

Here we identified a functional MazEF-dr system in the exceptionally stress-resistant bacterium . We showed that overexpression of the toxin MazF-dr inhibited the growth of . The toxic effect of MazF-dr was due to its sequence-specific endoribonuclease activity on RNAs containing a consensus 5'ACA3', and it could be neutralized by MazE-dr. The MazF-dr showed a special cleavage preference for the nucleotide present before the ACA sequence with the order by U>A>G>C. MazEF-dr mediated the death of cells under sub-lethal dose of stresses. The characteristics of programmed cell death (PCD) including membrane blebbing, loss of membrane integrity and cytoplasm condensation occurred in a fraction of the wild-type population at sub-lethal concentration of the DNA damaging agent mitomycin C (MMC); however, a MazEF-dr mutation relieved the cell death, suggesting that MazEF-dr mediated cell death through its endoribonuclease activity in response to DNA damage stress. The MazEF-dr-mediated cell death of a fraction of the population might serve as a survival strategy for the remaining population of under DNA damage stress.
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http://dx.doi.org/10.3389/fmicb.2017.01427DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5526972PMC
July 2017

A tamB homolog is involved in maintenance of cell envelope integrity and stress resistance of Deinococcus radiodurans.

Sci Rep 2017 04 6;7:45929. Epub 2017 Apr 6.

Key Laboratory for Nuclear-Agricultural Sciences of Chinese Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China.

The translocation and assembly module (TAM) in bacteria consists of TamA and TamB that form a complex to control the transport and secretion of outer membrane proteins. Herein, we demonstrated that the DR_1462-DR_1461-DR_1460 gene loci on chromosome 1 of Deinococcus radiodurans, which lacks tamA homologs, is a tamB homolog (DR_146T) with two tamB motifs and a DUF490 motif. Mutation of DR_146T resulted in cell envelope peeling and a decrease in resistance to shear stress and osmotic pressure, as well as an increase in oxidative stress resistance, consistent with the phenotype of a surface layer (S-layer) protein SlpA (DR_2577) mutant, demonstrating the involvement of DR_146T in maintenance of cell envelope integrity. The 123 kDa SlpA was absent and only its fragments were present in the cell envelope of DR_146T mutant, suggesting that DR_146T might be involved in maintenance of the S-layer. A mutant lacking the DUF490 motif displayed only a slight alteration in phenotype compared with the wild type, suggesting DUF490 is less important than tamB motif for the function of DR_146T. These findings enhance our understanding of the properties of the multilayered envelope in extremophilic D. radiodurans, as well as the diversity and functions of TAMs in bacteria.
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http://dx.doi.org/10.1038/srep45929DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5382914PMC
April 2017

Biosynthesis of gold nanoparticles by the extreme bacterium and an evaluation of their antibacterial properties.

Int J Nanomedicine 2016;11:5931-5944. Epub 2016 Nov 9.

Key Laboratory for Nuclear-Agricultural Sciences of Chinese Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences, Zhejiang University.

is an extreme bacterium known for its high resistance to stresses including radiation and oxidants. The ability of to reduce Au(III) and biosynthesize gold nanoparticles (AuNPs) was investigated in aqueous solution by ultraviolet and visible (UV/Vis) absorption spectroscopy, electron microscopy, X-ray diffraction (XRD), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). efficiently synthesized AuNPs from 1 mM Au(III) solution in 8 h. The AuNPs were of spherical, triangular and irregular shapes with an average size of 43.75 nm and a polydispersity index of 0.23 as measured by DLS. AuNPs were distributed in the cell envelope, across the cytosol and in the extracellular space. XRD analysis confirmed the crystallite nature of the AuNPs from the cell supernatant. Data from the FTIR and XPS showed that upon binding to proteins or compounds through interactions with carboxyl, amine, phospho and hydroxyl groups, Au(III) may be reduced to Au(I), and further reduced to Au(0) with the capping groups to stabilize the AuNPs. Biosynthesis of AuNPs was optimized with respect to the initial concentration of gold salt, bacterial growth period, solution pH and temperature. The purified AuNPs exhibited significant antibacterial activity against both Gram-negative () and Gram-positive () bacteria by damaging their cytoplasmic membrane. Therefore, the extreme bacterium can be used as a novel bacterial candidate for efficient biosynthesis of AuNPs, which exhibited potential in biomedical application as an antibacterial agent.
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http://dx.doi.org/10.2147/IJN.S119618DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5108609PMC
February 2017

DqsIR quorum sensing-mediated gene regulation of the extremophilic bacterium Deinococcus radiodurans in response to oxidative stress.

Mol Microbiol 2016 05 25;100(3):527-41. Epub 2016 Feb 25.

Key Laboratory for Nuclear-Agricultural Sciences of Chinese Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China.

Here, we show that AHLs can be employed by Deinococcus radiodurans, which belongs to the unique phylum Deinococcus-Thermus and is known for its cellular resistance to environmental stresses. An AHL-mediated quorum-sensing system (DqsI/DqsR) was identified in D. radiodurans. We found that under non-stress conditions, the AHL level was "shielded" by quorum quenching enzymes, whereas AHLs accumulated when D. radiodurans was exposed to oxidative stress. Upon exposure to H2 O2 , AHL synthetic enzymes (DqsI) were immediately induced, while the expression of quorum-quenching enzymes began to increase approximately 30 min after exposure to H2 O2 , as shown by time-course analyses of gene expression. Both dqsI mutant (DMDqsI) and dqsR mutant (MDqsR) were more sensitive to oxidative stress compared with the wild-type strain. Exogenous AHLs (5 μM) could completely restore the survival fraction of DMDqsI under oxidative stress. RNA-seq analysis showed that a number of genes involved in stress-response, cellular cleansing, and DNA repair had altered transcriptional levels in MDqsR. The DqsR, acting as a regulator of quorum sensing, controls gene expression along with AHLs. Hence, the DqsIR-mediated quorum sensing that mediates gene regulation is an adaptive strategy for D. radiodurans in response to oxidative stresses and is conserved in the extremophilic Deinococcus bacteria.
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http://dx.doi.org/10.1111/mmi.13331DOI Listing
May 2016

Expression of PprI from Deinococcus radiodurans Improves Lactic Acid Production and Stress Tolerance in Lactococcus lactis.

PLoS One 2015 12;10(11):e0142918. Epub 2015 Nov 12.

Key Laboratory for Nuclear-Agricultural Sciences of Chinese Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, 310029, China.

PprI is a general switch protein that regulates the expression of certain proteins involved in pathways of cellular resistance in the extremophilic bacterium Deinococcus radiodurans. In this study, we transformed pprI into Lactococcus lactis strain MG1363 using the lactococcal shuttle vector pMG36e and investigated its effects on the tolerance and lactic acid production of L. lactis while under stress. PprI was stably expressed in L. lactis as confirmed by western blot assays. L. lactis expressing PprI exhibited significantly improved resistance to oxidative stress and high osmotic pressure. This enhanced cellular tolerance to stressors might be due to the regulation of resistance-related genes (e.g., recA, recO, sodA, and nah) by pprI. Moreover, transformed L. lactis demonstrated increased lactic acid production, attributed to enhanced lactate dehydrogenase activity. These results suggest that pprI can improve the tolerance of L. lactis to environmental stresses, and this transformed bacterial strain is a promising candidate for industrial applications of lactic acid production.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0142918PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4643010PMC
July 2016

Autoinducer-2 signaling is involved in regulation of stress-related genes of Deinococcus radiodurans.

Arch Microbiol 2016 Jan 28;198(1):43-51. Epub 2015 Oct 28.

Key Laboratory for Nuclear-Agricultural Sciences of Chinese Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China.

Autoinducer-2 (AI-2) serves as a quorum-sensing signaling molecule that mediates both intraspecies and interspecies communication among bacteria, and plays critical roles in regulating various bacterial behaviors. In the present study, we investigated the functions of AI-2 signaling in the extremophilic bacterium Deinococcus radiodurans R1 by construction of the LuxS gene disruption mutant, survival phenotype assay and gene transcription assay. The gene mutant (DRΔLuxS), which was unable to produce AI-2, was significantly more sensitive to both gamma radiation and H2O2 compared with the wild-type strain. Addition of the wild-type-derived spent medium into the cell culture of DRΔLuxS fully restored the radioresistance of D. radiodurans. A higher level of reactive oxygen species accumulated in the mutant compared with the wild type under normal or oxidative stress. Quantitative real-time PCR assays showed that transcriptional levels of stress-related proteins, including catalase, extracellular nuclease, Dps-1 and ABC transporters, were decreased in DRΔLuxS, indicating that AI-2 is involved in regulation of stress-related genes of D. radiodurans. Hence, AI-2 signaling may contribute to the extreme resistance of D. radiodurans to radiation and oxidative stresses.
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http://dx.doi.org/10.1007/s00203-015-1163-7DOI Listing
January 2016

A PerR-like protein involved in response to oxidative stress in the extreme bacterium Deinococcus radiodurans.

Biochem Biophys Res Commun 2014 Jul 10;450(1):575-80. Epub 2014 Jun 10.

Key Laboratory for Nuclear-Agricultural Sciences of Chinese Ministry of Agriculture and Zhejiang Province, Institute of Nuclear-Agricultural Sciences, Zhejiang University, 310029 Hangzhou, China. Electronic address:

Response and defense systems against reactive oxygen species (ROS) contribute to the remarkable resistance of Deinococcus radiodurans to oxidative stress induced by oxidants or radiation. However, mechanisms involved in ROS response and defense systems of D. radiodurans are not well understood. Fur family proteins are important in ROS response. Only a single Fur homolog is predicted by sequence similarity in the current D. radiodurans genome database. Our bioinformatics analysis demonstrated an additional guanine nucleotide in the genome of D. radiodurans that is not in the database, leading to the discovery of another Fur homolog DrPerR. Gene disruption mutant of DrPerR showed enhanced resistance to hydrogen peroxide (H2O2) and increased catalase activity in cell extracts. Real-time PCR results indicated that DrPerR functions as a repressor of the catalase gene katE. Meanwhile, derepression of dps (DNA-binding proteins from starved cells) gene under H2O2 stress by DrPerR point to its regulatory role in metal ions hemostasis. Thus, DrPerR might function as a Fur homolog protein which is involved in ROS response and defense. These results help clarify the complicated regulatory network that responds to ROS stress in D. radiodurans.
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http://dx.doi.org/10.1016/j.bbrc.2014.06.015DOI Listing
July 2014