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1.
Environ Microbiol ; 2021 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-34837302

RESUMO

Antimicrobial-resistant pathogens in the environment and wastewater treatment systems, many of which are also important pollutant degraders and are difficult to control by traditional disinfection approaches, have become an unprecedented treat to ecological security and human health. Here, we propose the adoption of genetic editing techniques as a highly targeted, efficient and simple tool to control the risks of environmental pathogens at the source. An 'all-in-one' plasmid system was constructed in Aeromonas hydrophila to accurately identify and selectively inactivate multiple key virulence factor genes and antibiotic resistance genes via base editing, enabling significantly suppressed bacterial virulence and resistance without impairing their normal phenotype and pollutant-degradation functions. Its safe application for bioaugmented treatment of synthetic textile wastewater was also demonstrated. This genetic-editing technique may offer a promising solution to control the health risks of environmental microorganisms via targeted gene inactivation, thereby facilitating safer application of water treatment biotechnologies.

2.
Water Res ; 206: 117731, 2021 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-34626885

RESUMO

Biogenic ferrous sulfide nanoparticles (bio-FeS) as low-cost and green-synthesized nanomaterial are promising for heavy metals removal, but the need for complicated extraction, storage processes and the production of iron sludge still restrict their practical application. Here, a self-regenerable bio-hybrid consisting of bacterial cells and self-assembled bio-FeS was developed to efficiently remove chromium (Cr(VI)). A dense layer of bio-FeS was distributed on the cell surface and in the periplasmic space of Shewanella oneidensis MR-1, endowing the bacterium with good Cr(VI) tolerance and unusual activity for bio-FeS-mediated Cr(VI) reduction. An artificial transmembrane electron channel was constituted by the bio-FeS to facilitate extracellular electron pumping, enabling efficient regeneration of extracellular bio-FeS for continuous Cr(VI) reduction. The bio-hybrid maintained high activity within three consecutive treatment-regeneration cycles for treating both simulated Cr(VI)-containing wastewater (50 mg/L) and real electroplating wastewater. Importantly, its activity can be facilely and fully restored through bio-FeS re-synthesis or regeneration with replenished fresh bacteria. Overall, the bio-hybrid merges the self-regeneration ability of bacteria with high activity of bio-FeS , opening a promising new avenue for sustainable treatment of heavy metal- containing wastewater.


Assuntos
Cromo , Nanopartículas , Cromo/análise , Compostos Ferrosos , Shewanella , Águas Residuárias
3.
BMC Musculoskelet Disord ; 22(1): 867, 2021 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-34635092

RESUMO

BACKGROUND: Early versions of spinal muscular atrophy (SMA) scoliosis correction surgery often involved sublaminar devices. Recently, the utilization of pedicle screws has gained much popularity. Pedicle screws are generally believed to provide additional deformity correction, but pedicle size and rotational deformity limit their application in the thoracic spine, resulting in a hybrid construct involving pedicle screws and sublaminar wire. Studies of the efficacy of hybrid instrumentation in SMA scoliosis are often limited by the scarcity of the disease itself. In this study, we aimed to compare the surgical outcomes between hybrid constructs involving pedicle screws and sublaminar wire and sublaminar wire alone in patients with SMA scoliosis. METHODS: We retrospectively reviewed the clinical records and radiographic assessments of patients with SMA scoliosis who underwent corrective surgery between 1993 and 2017. The radiographic assessments included deformity correction and progressive changes in the major curve angle, pelvic tilt (PT) and coronal balance (CB). The correction of deformities was observed postoperatively and at the patient's 2-year follow-up to test the efficacy of each type of construct. RESULTS: Thirty-three patients were included in this study. There were 14 and 19 patients in the wiring and hybrid construct groups, respectively. The hybrid construct group demonstrated a higher major curve angle correction (50.5° ± 11.2° vs. 36.4° ± 8.4°, p < 0.001), a higher apical vertebral rotation correction (10.6° ± 3.9° vs. 4.8° ± 2.6°, p < 0.001), and a reduced progression of the major curve angle at the 2-year follow-up (5.1° ± 2.9° vs. 8.7° ± 4.8°, p < 0.001). A moderate correlation was observed between the magnitude of correction of the apical vertebral rotation angle and the major curve (r = 0.528, p = 0.002). CONCLUSION: This study demonstrated that hybrid instrumentation can provide a greater magnitude of correction in major curve and apical rotation as well as less major curve progression than sublaminar wire instrumentation alone in patients with SMA scoliosis. Level of evidence III.


Assuntos
Atrofia Muscular Espinal , Escoliose , Humanos , Atrofia Muscular Espinal/diagnóstico por imagem , Atrofia Muscular Espinal/cirurgia , Estudos Retrospectivos , Escoliose/diagnóstico por imagem , Escoliose/cirurgia , Coluna Vertebral , Resultado do Tratamento
4.
Biotechnol Bioeng ; 118(12): 4760-4770, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34546573

RESUMO

Members of the genus Aeromonas prevail in aquatic habitats and have a great potential in biological wastewater treatment because of their unique extracellular electron transfer (EET) capabilities. However, the mediated EET mechanisms of Aeromonas have not been fully understood yet, hindering their applications in biological wastewater treatment processes. In this study, the electron shuttles in Aeromonas hydrophila, a model and widespread strain in aquatic environments and wastewater treatment plants, were explored. A. hydrophila was found to produce both flavins and 2-amino-3-carboxy-1,4-naphthoquinone (ACNQ) as electron shuttles and utilize them to accelerate its EET for the bioreduction of various pollutants. The Mtr-like respiratory pathway was essential for the reduction of flavins, but not involved in the ACNQ reduction. The electron shuttle activity of ACNQ for pollutant bioreduction involved the redox reactions that occurred inside the cell. These findings deepen our understanding about the underlying EET mechanisms in dissimilatory metal reducing bacteria and provide new insights into the roles of the genus Aeromonas in biological wastewater treatment.

5.
Environ Sci Technol ; 55(17): 11997-12008, 2021 09 07.
Artigo em Inglês | MEDLINE | ID: mdl-34378391

RESUMO

Dissimilatory metal-reducing bacteria (DMRB) with extracellular electron transfer (EET) capability show great potential in bioremediating the subsurface environments contaminated by uranium through bioreduction and precipitation of hexavalent uranium [U(VI)]. However, the low EET efficiency of DMRB remains a bottleneck for their applications. Herein, we develop an engineered CRISPR platform to drive the extracellular electron pumping of Shewanella oneidensis, a representative DMRB species widely present in aquatic environments. The CRISPR platform allows for highly efficient and multiplex genome editing and rapid platform elimination post-editing in S. oneidensis. Enabled by such a platform, a genomic promoter engineering strategy (GPS) for genome-widely engineering the EET-encoding gene network was established. The production of electron conductive Mtr complex, synthesis of electron shuttle flavin, and generation of NADH as intracellular electron carrier are globally optimized and promoted, leading to a significantly enhanced EET ability. Applied to U(VI) bioreduction, the edited strains achieve up to 3.62-fold higher reduction capacity over the control. Our work endows DMRB with an enhanced ability to remediate the radionuclides-contaminated environments and provides a gene editing approach to handle the growing environmental challenges of radionuclide contaminations.


Assuntos
Shewanella , Urânio , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Transporte de Elétrons , Elétrons , Shewanella/genética
7.
Environ Sci Technol ; 55(11): 7531-7540, 2021 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-33974407

RESUMO

Cadmium ion (Cd2+) is a common environmental pollutant with high biotoxicity. Interestingly, the Cd2+ biotoxicity can be alleviated by the coexisting selenite (SeO32-), which induces the formation of cadmium selenide-rich nanoparticles (CdSe NPs) under the function of thiol-capping peptides. However, the detailed biochemical mechanisms by which Cd and Se are synergistically transformed into CdSe NPs in living organisms remain unclear so far. Here, we shed light on the molecular basis of such biotransformation processes in Caenorhabditis elegans by focusing on the roles of several key thiol-capping peptides. By monitoring the compositional and structural changes of the Cd and Se species and the genetic-level responses of nematodes, we revealed the specific roles of glutathione (GSH) and phytochelatins (PCs) in mediating the CdSe NP formation. With the aid of in vitro bioassembly assay and density functional theory calculations, the detailed Cd-Se interaction pathways were further deciphered: the ingested Cd binds predominantly to GSH and PCs in sequence, then further interacts with selenocysteine to form tetrahedral-structured PC2-Cd2-Sec2 complex, and ultimately grows into CdSe NPs. This work provides molecular-level insights into the Cd-Se interaction in C. elegans and lays a basis for controlling the ecological and health risks of heavy metals in polluted environment.


Assuntos
Cádmio , Selênio , Animais , Biotransformação , Caenorhabditis elegans , Glutationa/metabolismo , Fitoquelatinas/metabolismo , Compostos de Sulfidrila
8.
ACS Appl Mater Interfaces ; 13(17): 19846-19854, 2021 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-33886264

RESUMO

Incorporating artificial photosensitizers with microorganisms has recently been recognized as an effective way to convert light energy into chemical energy. However, the incorporated biosystem is usually constructed in an extracellular manner and is vulnerable to the external environment. Here, we develop an intracellular hybrid biosystem in a higher organism protozoa Tetrahymena pyriformis, in which the in vivo synthesized CdS nanoparticles trigger photoreduction of nitrobenzene into aniline under visible-light irradiation. Integrating a photosensitizer CdS into T. pyriformis enables the photosensitizer CdS, inherent nitroreductase, and the cytoplasmic reductive substance in T. pyriformis to synergistically engage in the photocatalysis process, generating a greatly enhanced aniline yield with a 40-fold increment. Moreover, building an intracellular hybrid biosystem in mutant T. pyriformis could even grant it new capability of reducing nitrobenzene into aniline under visible-light irradiation. Such an intracellular hybrid biosystem paves a new way to functionalize higher organisms and diversify light energy conversion.


Assuntos
Luz , Tetrahymena pyriformis/metabolismo , Compostos de Anilina/metabolismo , Compostos de Cádmio/química , Compostos de Cádmio/farmacologia , Catálise , Nanopartículas Metálicas/química , Microscopia de Fluorescência/métodos , Mutação , Nitrobenzenos/metabolismo , Fármacos Fotossensibilizantes/química , Fármacos Fotossensibilizantes/farmacologia , Sulfetos/química , Sulfetos/farmacologia , Tetrahymena pyriformis/genética
9.
Water Res ; 191: 116799, 2021 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-33453457

RESUMO

Peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) for wastewater treatment have recently attracted widespread interests. However, the degradation of organic pollutants via traditional radical-dominated pathway is severely limited by the side reactions between radicals and the co-existing inorganic anions, especially under high salinity conditions. Herein, an efficient Fe/O co-doped g-C3N4nanosheet catalyst was synthesized to dominantly activate PMS through a dual non-radical pathway with the singlet oxygen and high-valent iron-oxo species (Fe(V)=O). The rapid degradation of model pollutant bisphenol A (BPA) was achieved by dosing PMS (1 mM), catalyst (0.1 g/L) in a simulated high-salt wastewater (≥200 mM) of the developed Fe/O-doped g-C3N4+PMS system with a reaction rate constant of 1204-fold higher than that in g-C3N4+PMS system. The O and Fe co-dopants could reconfigurate the electronic structure of pristine g-C3N4 to produce more non-radical active species. The formed Fe(V)=O played a main role in the BPA degradation by promoting electron transfer from BPA molecule to the "metastable PMS/catalyst complex", which was verified by electrochemical tests and density functional theory calculations. The auxiliary transient productions of ·OH+SO4·- species were also favorable for the pollutant degradation. Excellent reusability in a wide pH range confirmed the practical application prospects of the Fe/O-doped g-C3N4+PMS system. The successive addition of PMS with a low dosage into the system rich in pollutants was confirmed to favor the PMS utilization. Our work unveils the potential applications of a non-radical dominated process for the decontamination of organic pollutants in saline water.


Assuntos
Poluentes Ambientais , Descontaminação , Peróxidos , Salinidade
10.
Angew Chem Int Ed Engl ; 60(1): 274-280, 2021 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-32965786

RESUMO

Transition metal (TM)-based bimetallic spinel oxides can efficiently activate peroxymonosulfate (PMS) presumably attributed to enhanced electron transfer between TMs, but the existing model cannot fully explain the efficient TM redox cycling. Here, we discover a critical role of TM-O covalency in governing the intrinsic catalytic activity of Co3-x Mnx O4 spinel oxides. Experimental and theoretical analysis reveals that the Co sites significantly raises the Mn valence and enlarges Mn-O covalency in octahedral configuration, thereby lowering the charge transfer energy to favor MnOh -PMS interaction. With appropriate MnIV /MnIII ratio to balance PMS adsorption and MnIV reduction, the Co1.1 Mn1.9 O4 exhibits remarkable catalytic activities for PMS activation and pollutant degradation, outperforming all the reported TM spinel oxides. The improved understandings on the origins of spinel oxides activity for PMS activation may inspire the development of more active and robust metal oxide catalysts.

11.
Anal Chem ; 93(3): 1443-1450, 2021 01 26.
Artigo em Inglês | MEDLINE | ID: mdl-33369381

RESUMO

A prophage comprises a bacteriophage genome that has integrated into a host bacterium's DNA, which generally permits the cell to grow and divide normally. However, the prophage can be induced by various stresses, or induction can occur spontaneously. After prophage induction, viral replication and production of endolysins begin until the cell lyses and phage particles are released. However, the heterogeneity of prophage induction and lysis of individual cells in a population and the dynamics of a cell undergoing lysis by prophage induction have not been fully characterized. Here, we used Raman tweezers and live-cell phase-contrast microscopy to characterize the Raman spectral and cell length changes that occur during the lysis of individual Bacillus subtilis cells from spores that carry PBSX prophage during spores' germination, outgrowth, and then vegetative growth. Major findings of this work are as follows: (i) After addition of xylose to trigger prophage induction, the intensities of Raman spectral bands associated with nucleic acids of single cells in induced cultures gradually fell to zero, in contrast to the much smaller changes in protein band intensities and no changes in nucleic acid bands in uninduced cultures; (ii) the nucleic acid band intensities from an individual induced cell exhibited a rapid decrease, following a long lag period; (iii) after the addition of nutrient-rich medium with xylose, single spores underwent a long period (228 ± 41.4 min) for germination, outgrowth, and vegetative growth, followed by a short period of cell burst in 1.5 ± 0.8 min at a cell length of 8.2 ± 5.5 µm; (iv) the latent time (Tlatent) between the addition of xylose and the start of cell burst was heterogeneous in cell populations; however, the period (ΔTburst) from the latent time to the completion of cell lysis was quite small; (v) in a poor medium with l-alanine alone, addition of xylose caused prophage induction following spore germination but with longer Tlatent and ΔTburst times and without cell elongation; (vi) spontaneous prophage induction and lysis of individual cells from spores in a minimal nutrient medium were observed without xylose addition, and cell length prior to cell lysis was ∼4.1 µm, but spontaneous prophage induction was not observed in a rich medium; (vii) in a rich medium, addition of xylose at a time well after spore germination and outgrowth significantly shortened the average Tlatent time. The results of this study provide new insights into the heterogeneity and dynamics of lysis of individual B. subtilis cells derived from spores upon prophage induction.


Assuntos
Bacillus subtilis/citologia , Análise de Célula Única , Esporos Bacterianos/crescimento & desenvolvimento , Bacillus subtilis/metabolismo , Microscopia de Contraste de Fase , Pinças Ópticas , Análise Espectral Raman , Esporos Bacterianos/química , Esporos Bacterianos/metabolismo
12.
Environ Microbiol ; 23(2): 1238-1255, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33369000

RESUMO

The advances in synthetic biology bring exciting new opportunities to reprogram microorganisms with novel functionalities for environmental applications. For real-world applications, a genetic tool that enables genetic engineering in a stably genomic inherited manner is greatly desired. In this work, we design a novel genetic device for rapid and efficient genome engineering based on the intron-encoded homing-endonuclease empowered genome editing (iEditing). The iEditing device enables rapid and efficient genome engineering in Shewanella oneidensis MR-1, the representative strain of the electroactive bacteria group. Moreover, combining with the Red or RecET recombination system, the genome-editing efficiency was greatly improved, up to approximately 100%. Significantly, the iEditing device itself is eliminated simultaneously when genome editing occurs, thereby requiring no follow-up to remove the encoding system. Then, we develop a new extracellular electron transfer (EET) engineering strategy by programming the parallel EET systems to enhance versatile EET. The engineered strains exhibit sufficiently enhanced electron output and pollutant reduction ability. Furthermore, this device has demonstrated its great potential to be extended for genome editing in other important microbes. This work provides a useful and efficient tool for the rapid generation of synthetic microorganisms for various environmental applications.


Assuntos
Fontes de Energia Bioelétrica/microbiologia , Elétrons , Engenharia Genética/métodos , Genoma Bacteriano/genética , Biodegradação Ambiental , Transporte de Elétrons/genética , Poluentes Ambientais/metabolismo , Edição de Genes/instrumentação , Engenharia Genética/instrumentação , Recombinação Genética , Shewanella/genética , Shewanella/metabolismo
14.
Curr Opin Chem Biol ; 59: 140-146, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32769012

RESUMO

Exoelectrogens are distinct from other bacteria owing to their unique extracellular electron transfer (EET) abilities that allow for anaerobic respiration with various external redox-active surfaces, including electrode and metal oxides. Although the EET process is known to trigger diverse extracellular redox reactions, the reverse impact has been long overlooked. Recent evidences show that exoelectrogens can sense the potential changes of external surfaces and alter their EET strategies accordingly, which imparts them remarkable abilities in adapting to diverse and redox-variable environment. This mini-review provides a condensed overview and critical analysis about the recent discoveries on redox-dependent EET pathways of exoelectrogens, with focus on Geobacter sulfurreducens and Shewanella oneidensis. We summarize the detailed responses of various EET components, analyze the drives and mechanisms of such responses, highlight the diversity of EET dynamics among different bacterial species and under integrated effects of redox potential and surface chemistry, and discusses the future research needs.


Assuntos
Geobacter/metabolismo , Shewanella/metabolismo , Transporte de Elétrons , Elétrons , Oxirredução
15.
Proc Natl Acad Sci U S A ; 117(37): 23001-23010, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32855303

RESUMO

The unique extracellular electron transfer (EET) ability has positioned electroactive bacteria (EAB) as a major class of cellular chassis for genetic engineering aimed at favorable environmental, energy, and geoscience applications. However, previous efforts to genetically enhance EET ability have often impaired the basal metabolism and cellular growth due to the competition for the limited cellular resource. Here, we design a quorum sensing-based population-state decision (PSD) system for intelligently reprogramming the EET regulation system, which allows the rebalanced allocation of the cellular resource upon the bacterial growth state. We demonstrate that the electron output from Shewanella oneidensis MR-1 could be greatly enhanced by the PSD system via shifting the dominant metabolic flux from initial bacterial growth to subsequent EET enhancement (i.e., after reaching a certain population-state threshold). The strain engineered with this system achieved up to 4.8-fold EET enhancement and exhibited a substantially improved pollutant reduction ability, increasing the reduction efficiencies of methyl orange and hexavalent chromium by 18.8- and 5.5-fold, respectively. Moreover, the PSD system outcompeted the constant expression system in managing EET enhancement, resulting in considerably enhanced electron output and pollutant bioreduction capability. The PSD system provides a powerful tool for intelligently managing extracellular electron transfer and may inspire the development of new-generation smart bioelectrical devices for various applications.


Assuntos
Transporte de Elétrons/fisiologia , Shewanella/fisiologia , Respiração Celular/fisiologia , Cromo/metabolismo , Elétrons , Percepção de Quorum/fisiologia , Shewanella/metabolismo
16.
Chin J Integr Med ; 26(6): 405-411, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32476098

RESUMO

Parkinson's disease (PD) was first formally described by James Parkinson in 1817, but the shaking of limbs was described in the literature of several ancient civilizations, such as ancient Chinese civilization and ancient Indian civilization. Historically, botanical drugs were used as the main source for the treatment of such kind of disorders. In Western countries, plant extracts also occupied an important place in the earlier medications of PD. With the adventure of synthetic drugs, the role of plant-derived drugs in management of PD has been diminished. Nowadays, there is still no cure for PD, dopaminergic (DA) medication is the treatment of choice, which is just designed to ameliorate symptoms of PD, and long-term use of DA medication will result in reduced efficacy and severe adverse reactions. It is necessary to explore new methods for the treatment of PD. Chinese medicine (CM) developed a holistic and unique theoretical system, and botanical drugs are widely used in practice for more than two millennia. Modern pharmacological studies have proved that Chinese herbs have potential therapeutic effects on PD, such as enhancing neurotrophic activity, clearing protein aggregates, regulating neuroinflammation, etc. All the advances provide us with hope for developing CM as a mainstream medication for treating PD.


Assuntos
Medicina Tradicional/métodos , Doença de Parkinson/terapia , Fitoterapia/métodos , Plantas Medicinais , Humanos
17.
Environ Sci Technol ; 54(6): 3599-3608, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32062962

RESUMO

Pursuing efficient approaches to promote the extracellular electron transfer (EET) of extracellular respiratory bacteria is essential to their application in environmental remediation and waste treatment. Here, we report a new strategy of tuning electron flux by clustered regularly interspaced short palindromic repeat (CRISPR)-ddAsCpf1-based rediverting (namely STAR) to enhance the EET capacity of Shewanella oneidensis MR-1, a model extracellular respiratory bacterium widely present in the environment. The developed CRISPR-ddAsCpf1 system enabled approximately 100% gene repression with the green fluorescent protein (GFP) as a reporter. Using a WO3 probe, 10 representative genes encoding for putative competitive electron transfer proteins were screened, among which 7 genes were identified as valid targets for EET enhancement. Repressing the valid genes not only increased the transcription level of the l-lactate metabolism genes but also affected the genes involved in direct and indirect EET. Increased riboflavin production was also observed. The feasibility of this strategy to enhance the bioreduction of methyl orange, an organic pollutant, and chromium, a typical heavy metal, was demonstrated. This work implies a great potential of the STAR strategy with the CIRPSR-ddAsCpf1 system for enhancing bacterial EET to favor more efficient environmental remediation applications.


Assuntos
Poluentes Ambientais , Shewanella , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas , Transporte de Elétrons , Elétrons
18.
Bioresour Technol ; 302: 122865, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32004814

RESUMO

Fermentative caproate production from wastewater is attractive but is currently limited by the low product purity and concentration. In this work, continuous, selective production of caproate from acetate and ethanol, the common products of wastewater anaerobic fermentation, was achieved in an anaerobic membrane bioreactor (AnMBR). The reactor was continuously operated for over 522 days without need for chemical cleaning. With an ethanol-to-acetate ratio of 3.0, the effluent caproate concentration was 2.62 g/L on average and the caproate ratio in liquid products reached 74%. Further raising the influent ethanol content slightly increased the effluent caproate level but lowered the product selectivity and resulted in microbial inhibition. The Clostridia (the major caproate-producing bacteria) and Methanobacterium species (which consume hydrogen to alleviate microbial inhibition) was significantly enriched in the acclimated sludge. Our results imply a great potential of utilizing AnMBR to recover caproate from the effluent of wastewater acidogenic fermentation process.


Assuntos
Reatores Biológicos , Caproatos , Anaerobiose , Bactérias Anaeróbias , Fermentação
19.
Anal Chem ; 92(5): 3990-3997, 2020 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-32020800

RESUMO

Mercury (Hg), as a highly harmful environmental pollutant, poses severe ecological and health risks even at low concentrations. Accurate and sensitive methods for detecting Hg2+ ions in aquatic environments are highly needed. In this work, we developed a highly sensitive fluorescence sensor for Hg2+ detection with an integrated use of biosynthetic CdSe/CdS quantum dots (QDs) and liposome carrier signal amplification. To construct such a sensor, three single-stranded DNA probes were rationally designed based on the thymine-Hg2+-thymine (T-Hg2+-T) coordination chemical principles and by taking advantage of the biocompatibility and facile-modification properties of the biosynthetic QDs. Hg2+ could be determined in a range from 0.25 to 100 nM with a detection limit of 0.01 nM, which met the requirements of environmental sample detection. The sensor also exhibited a high selectivity for Hg2+ detection in the presence of other high-level metal ions. A satisfactory capacity of the sensor for detecting environmental samples including tap water, river water, and landfill leachate was also demonstrated. This work opens up a new application scenario for biosynthetic QDs and holds a great potential for environmental monitoring applications.


Assuntos
Lipossomos/química , Mercúrio/análise , Pontos Quânticos/química , Espectrometria de Fluorescência/métodos , Compostos de Cádmio/química , DNA de Cadeia Simples/química , Monitoramento Ambiental , Água Doce/análise , Concentração de Íons de Hidrogênio , Limite de Detecção , Compostos de Selênio/química , Sulfetos/química , Timina/química , Poluentes Químicos da Água/análise
20.
Biotechnol Bioeng ; 117(5): 1294-1303, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32048726

RESUMO

The bioreduction capacity of Cr(VI) by Shewanella is mainly governed by its bidirectional extracellular electron transfer (EET). However, the low bidirectional EET efficiency restricts its wider applications in remediation of the environments contaminated by Cr(VI). Cyclic adenosine 3',5'-monophosphate (cAMP) commonly exists in Shewanella strains and cAMP-cyclic adenosine 3',5'-monophosphate receptor protein (CRP) system regulates multiple bidirectional EET-related pathways. This inspires us to strengthen the bidirectional EET through elevating the intracellular cAMP level in Shewanella strains. In this study, an exogenous gene encoding adenylate cyclase from the soil bacterium Beggiatoa sp. PS is functionally expressed in Shewanella oneidensis MR-1 (the strain MR-1/pbPAC) and a MR-1 mutant lacking all endogenous adenylate cyclase encoding genes (the strain Δca/pbPAC). The engineered strains exhibit the enhanced bidirectional EET capacities in microbial electrochemical systems compared with their counterparts. Meanwhile, a three times more rapid reduction rate of Cr(VI) is achieved by the strain MR-1/pbPAC than the control in batch experiments. Furthermore, a higher Cr(VI) reduction efficiency is also achieved by the strain MR-1/pbPAC in the Cr(VI)-reducing biocathode experiments. Such a bidirectional enhancement is attributed to the improved production of cAMP-CRP complex, which upregulates the expression levels of the genes encoding the c-type cytochromes and flavins synthetic pathways. Specially, this strategy could be used as a broad-spectrum approach for the other Shewanella strains. Our results demonstrate that elevating the intracellular cAMP levels could be an efficient strategy to enhance the bidirectional EET of Shewanella strains and improve their pollutant transformation capacity.


Assuntos
Cromo , AMP Cíclico , Shewanella , Adenilil Ciclases/genética , Adenilil Ciclases/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Beggiatoa/enzimologia , Beggiatoa/genética , Cromo/análise , Cromo/metabolismo , AMP Cíclico/análise , AMP Cíclico/metabolismo , Transporte de Elétrons , Engenharia Metabólica , Oxirredução , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Shewanella/citologia , Shewanella/genética , Shewanella/metabolismo
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