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1.
Nucleic Acids Res ; 48(19): 11054-11067, 2020 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-33045733

RESUMO

The two-gene module HEPN/MNT is predicted to be the most abundant toxin/antitoxin (TA) system in prokaryotes. However, its physiological function and neutralization mechanism remains obscure. Here, we discovered that the MntA antitoxin (MNT-domain protein) acts as an adenylyltransferase and chemically modifies the HepT toxin (HEPN-domain protein) to block its toxicity as an RNase. Biochemical and structural studies revealed that MntA mediates the transfer of three AMPs to a tyrosine residue next to the RNase domain of HepT in Shewanella oneidensis. Furthermore, in vitro enzymatic assays showed that the three AMPs are transferred to HepT by MntA consecutively with ATP serving as the substrate, and this polyadenylylation is crucial for reducing HepT toxicity. Additionally, the GSX10DXD motif, which is conserved among MntA proteins, is the key active motif for polyadenylylating and neutralizing HepT. Thus, HepT/MntA represents a new type of TA system, and the polyadenylylation-dependent TA neutralization mechanism is prevalent in bacteria and archaea.


Assuntos
Proteínas de Bactérias/metabolismo , Toxinas Bacterianas/metabolismo , Shewanella/metabolismo , Sistemas Toxina-Antitoxina
2.
Appl Environ Microbiol ; 86(23)2020 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-32978123

RESUMO

The outer membrane c-type cytochromes (c-Cyts) OmcA and MtrC in Shewanella are key terminal reductases that bind and transfer electrons directly to iron (hydr)oxides. Although the amounts of OmcA and MtrC at the cell surface and their molecular structures are largely comparable, MtrC is known to play a more important role in dissimilatory iron reduction. To explore the roles of these outer membrane c-Cyts in the interaction of Shewanella oneidensis MR-1 with iron oxides, the processes of attachment of S. oneidensis MR-1 wild type and c-type cytochrome-deficient mutants (the ΔomcA, ΔmtrC, and ΔomcA ΔmtrC mutants) to goethite are compared via quartz crystal microbalance with dissipation monitoring (QCM-D). Strains with OmcA exhibit a rapid initial attachment. The quantitative model for QCM-D responses reveals that MtrC enhances the contact area and contact elasticity of cells with goethite by more than one and two times, respectively. In situ attenuated total reflectance Fourier transform infrared two-dimensional correlation spectroscopic (ATR-FTIR 2D-CoS) analysis shows that MtrC promotes the initial interfacial reaction via an inner-sphere coordination. Atomic force microscopy (AFM) analysis demonstrates that OmcA enhances the attractive force between cells and goethite by about 60%. As a result, OmcA contributes to a higher attractive force with goethite and induces a rapid short-term attachment, while MtrC is more important in the longer-term interaction through an enhanced contact area, which promotes interfacial reactions. These results reveal that c-Cyts OmcA and MtrC adopt different mechanisms for enhancing the attachment of S. oneidensis MR-1 cells to goethite. It improves our understanding of the function of outer membrane c-Cyts and the influence of cell surface macromolecules in cell-mineral interactions.IMPORTANCE Shewanella species are one group of versatile and widespread dissimilatory iron-reducing bacteria, which are capable of respiring insoluble iron minerals via six multiheme c-type cytochromes. Outer membrane c-type cytochromes (c-Cyts) OmcA and MtrC are the terminal reductases in this pathway and have comparable protein structures. In this study, we elucidate the different roles of OmcA and MtrC in the interaction of S. oneidensis MR-1 with goethite at the whole-cell level. OmcA confers enhanced affinity toward goethite and results in rapid attachment. Meanwhile, MtrC significantly increases the contact area of bacterial cells with goethite and promotes the interfacial reaction, which may explain its central role in extracellular electron transfer. This study provides novel insights into the role of bacterial surface macromolecules in the interfacial interaction of bacteria with minerals, which is critical to the development of a comprehensive understanding of cell-mineral interactions.


Assuntos
Aderência Bacteriana/genética , Proteínas de Bactérias/genética , Grupo dos Citocromos c/genética , Compostos de Ferro/metabolismo , Minerais/metabolismo , Shewanella/genética , Proteínas de Bactérias/metabolismo , Grupo dos Citocromos c/metabolismo , Shewanella/metabolismo
3.
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
4.
Nat Commun ; 11(1): 4087, 2020 08 14.
Artigo em Inglês | MEDLINE | ID: mdl-32796822

RESUMO

By electronically wiring-up living cells with abiotic conductive surfaces, bioelectrochemical systems (BES) harvest energy and synthesize electric-/solar-chemicals with unmatched thermodynamic efficiency. However, the establishment of an efficient electronic interface between living cells and abiotic surfaces is hindered due to the requirement of extremely close contact and high interfacial area, which is quite challenging for cell and material engineering. Herein, we propose a new concept of a single cell electron collector, which is in-situ built with an interconnected intact conductive layer on and cross the individual cell membrane. The single cell electron collector forms intimate contact with the cellular electron transfer machinery and maximizes the interfacial area, achieving record-high interfacial electron transfer efficiency and BES performance. Thus, this single cell electron collector provides a superior tool to wire living cells with abiotic surfaces at the single-cell level and adds new dimensions for abiotic/biotic interface engineering.


Assuntos
Eletroquímica/métodos , Biofilmes/crescimento & desenvolvimento , Catálise , Eletrodos , Microscopia Eletroquímica de Varredura , Microscopia Eletrônica de Transmissão , Shewanella/metabolismo , Shewanella/ultraestrutura
5.
Arch Microbiol ; 202(10): 2711-2726, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32728830

RESUMO

In recent years, bioremediation is considered as an efficient method to remove the pollutants from the industrial wastewater. In this study, quantitative gene expressions (Real-time RT-PCR) of mtr gene cluster (mtrA, mtrB, mtrC, mtrD, mtrE, mtrF and omcA) in five different uranium concentrations (0.1, 0.25, 0.5, 1 and 2 mM) were performed with ICP and microscopic live cell counting analysis under anaerobic condition, by Shewanella RCRI7 as a native bacterium. The results indicated that the amount of uranium removal and live-cell counting were decreased in the higher uranium concentrations (1 and 2 mM), due to the uranium toxicity, suggesting 0.5 mM as the optimum uranium concentration for Shewanella RCRI7 resistance. The expression of mtrCED and omcA genes presented increasing trend in the lower uranium concentrations (0.1, 0.25 and 0.5 mM) and a decreasing trend in 1 and 2 mM, while mtrABF, presented an inverse pattern, proving the alternative role of mtrF for mtrC and omcA, as the substantial multiheme cytochromes in Extracellular Electron Transfer (EET) pathway. These data are a proof of these gene vital roles in the EET pathway, proposing them for genetic engineering toward EET optimization, as the certain pathway in heavy metal bioremediation process.


Assuntos
Biodegradação Ambiental , Proteínas de Membrana Transportadoras/genética , Shewanella/genética , Shewanella/metabolismo , Urânio/análise , Poluentes Químicos da Água/análise , Proteínas da Membrana Bacteriana Externa/genética , Grupo dos Citocromos c/genética , Transporte de Elétrons/genética , Família Multigênica/genética , Oxirredução , Águas Residuárias/química , Poluição da Água/análise
6.
Chemosphere ; 252: 126571, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32224361

RESUMO

An exoelectrogens, Shewanella oneidensis MR-1 (S. oneidensis MR-1), was supplied to a microbial fuel cell (MFC) to enhance the degradation of a recalcitrant organic compound, o-xylene. The experimental results revealed that, with the addition of the S. oneidensis MR-1, the o-xylene removal efficiency increased by 35-76% compared with the original MFC. The presence of the S. oneidensis MR-1 not only improved the activity of the biofilm in the bioanode but also developed the connections between the bacteria by nanowires. Therefore, the maximum power density increased from 52.1 to 92.5 mW/m3 after the addition of the S. oneidensis MR-1. The microbial community analysis showed that adding the S. oneidensis MR-1 increased the biodiversity in bioanode. The dominant exoelectrogens shifted from Zoogloea sp., Delftia sp., Achromobacter sp., Acinetobacter sp., Chryseobacterium sp., and Stenotrophomonas sp. to Zoogloea sp., Delftia sp., Shewanella sp., Achromobacter sp., Hydrogenophaga sp., Sedimentibacter sp. and Chryseobacterium sp.. Furthermore, the cyclic voltammetry analysis showed that the outer membrane bound protein complex of OmcA-MtrCAB was involved as direct electron transfer pathway in the S. oneidensis MR-1 containing bioanode. We believed that this work is promising to provide optional strategy for efficient VOCs degradation by adjusting the microbial community in the bioanode.


Assuntos
Fontes de Energia Bioelétrica/microbiologia , Shewanella/fisiologia , Xilenos/metabolismo , Biofilmes , Gases , Nanofios , Shewanella/metabolismo
7.
Microbes Environ ; 35(2)2020.
Artigo em Inglês | MEDLINE | ID: mdl-32147604

RESUMO

To identify exoelectrogens involved in the generation of electricity from complex organic matter in coastal sediment (CS) microbial fuel cells (MFCs), MFCs were inoculated with CS obtained from tidal flats and estuaries in the Tokyo bay and supplemented with starch, peptone, and fish extract as substrates. Power output was dependent on the CS used as inocula and ranged between 100 and 600 mW m-2 (based on the projected area of the anode). Analyses of anode microbiomes using 16S rRNA gene amplicons revealed that the read abundance of some bacteria, including those related to Shewanella algae, positively correlated with power outputs from MFCs. Some fermentative bacteria were also detected as major populations in anode microbiomes. A bacterial strain related to S. algae was isolated from MFC using an electrode plate-culture device, and pure-culture experiments demonstrated that this strain exhibited the ability to generate electricity from organic acids, including acetate. These results suggest that acetate-oxidizing S. algae relatives generate electricity from fermentation products in CS-MFCs that decompose complex organic matter.


Assuntos
Acetatos/metabolismo , Bactérias/metabolismo , Fontes de Energia Bioelétrica/microbiologia , Eletricidade , Sedimentos Geológicos/microbiologia , Shewanella/metabolismo , Bactérias/classificação , Eletrodos , Fermentação , Microbiota/genética , RNA Ribossômico 16S/genética , Shewanella/genética , Tóquio
8.
J Biotechnol ; 312: 56-62, 2020 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-32151642

RESUMO

Whole-cell biocatalysts have numerous advantages including ease of preparation and coenzyme recovery over purified industrially used enzymes. However, the cell membrane can occasionally hinder cytoplasmic diffusion of the substrate, resulting in reduced biotransformation efficiency. Psychrophiles can grow and reproduce at low temperatures; their cell membranes are highly flexible, and their permeability can be improved via heat treatment at a moderate temperature. The aim of this study was to generate a psychrophile-based simple biocatalyst (PSCats) using Shewanella livingstonensis Ac10. This biocatalyst contained two enzymes that were heterologously expressed and converted citric acid to itaconic acid, thereby serving as a potential platform replacing the petroleum-based counterparts. The efficiency of the biocatalyst was increased via heat treatment at 45 °C for 15 min, and itaconic acid productivity of the cells after heat treatment (1.41 g/L/h) was increased around 6-fold in comparison with those without heat treatment (0.22 g/L/h). A large part of the productivity remained (67.3 %) when the cells were reused for 5 times (10 h for each reaction). Therefore, the potential of this heat-permeabilized psychrophile host to increase the productivity of whole-cell biocatalyst was proved; however, further research is necessary to understand the underlying mechanism.


Assuntos
Permeabilidade da Membrana Celular/efeitos dos fármacos , Permeabilidade da Membrana Celular/fisiologia , Enzimas/farmacologia , Shewanella/metabolismo , Succinatos/metabolismo , Aconitato Hidratase , Ácido Cítrico/metabolismo , Temperatura Baixa , Citoplasma/metabolismo , Escherichia coli/genética , Temperatura Alta , Metaboloma , Shewanella/genética , Shewanella/crescimento & desenvolvimento
9.
PLoS One ; 15(3): e0229990, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32163461

RESUMO

A method was developed and validated for low-level detection of glucose. The method involves quantitation of glucose though derivitization with 1-phenyl-3-methyl-5-pyrazolone (PMP) and HPLC-DAD analysis. The developed method was found to be accurate and robust achieving detection limits as low as 0.09 nM. The applicability of the method was tested against microbial samples with glucose acting as a carbon fuel source. The method was shown to be able to accurately discriminate and quantify PMP-glucose derivatives within Shewanella oneidensis MR-1 samples. The method proved capable at examining glucose usage during the early hours of microbial growth, with detectable usage occurring as early as two hours. S. oneidensis cultures were found to grow more effectively in the presence of oxygen which coincided with more efficient glucose usage. Glucose usage further increased in the presence of competing electron acceptors. The rate at which S. oneidensis reached exponential growth was affected by the presence of ferric iron under microaerobic conditions. Such samples reached exponential growth approximately two hours sooner than aerobic samples.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Edaravone/química , Glucose/análise , Shewanella/metabolismo , Cromatografia de Fase Reversa , Compostos Férricos/química , Glucose/química , Limite de Detecção , Reprodutibilidade dos Testes , Shewanella/crescimento & desenvolvimento
10.
Nat Commun ; 11(1): 1379, 2020 03 13.
Artigo em Inglês | MEDLINE | ID: mdl-32170166

RESUMO

Bioelectricity generation, by Shewanella oneidensis (S. oneidensis) MR-1, has become particularly alluring, thanks to its extraordinary prospects for energy production, pollution treatment, and biosynthesis. Attempts to improve its technological output by modification of S. oneidensis MR-1 remains complicated, expensive and inefficient. Herein, we report on the augmentation of S. oneidensis MR-1 with carbon dots (CDs). The CDs-fed cells show accelerated extracellular electron transfer and metabolic rate, with increased intracellular charge, higher adenosine triphosphate level, quicker substrate consumption and more abundant extracellular secretion. Meanwhile, the CDs promote cellular adhesion, electronegativity, and biofilm formation. In bioelectrical systems the CDs-fed cells increase the maximum current value, 7.34 fold, and power output, 6.46 fold. The enhancement efficacy is found to be strongly dependent on the surface charge of the CDs. This work demonstrates a simple, cost-effective and efficient route to improve bioelectricity generation of S. oneidensis MR-1, holding promise in all relevant technologies.


Assuntos
Fontes de Energia Bioelétrica , Carbono/metabolismo , Shewanella/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Materiais Biocompatíveis , Biotecnologia , Eletricidade , Técnicas Eletroquímicas , Transporte de Elétrons , Shewanella/genética , Shewanella/ultraestrutura
11.
Appl Environ Microbiol ; 86(7)2020 03 18.
Artigo em Inglês | MEDLINE | ID: mdl-32005730

RESUMO

The siderophore synthetic system in Shewanella species is able to synthesize dozens of macrocyclic siderophores in vitro with synthetic precursors. In vivo, however, although three siderophores are produced naturally in Shewanella algae B516, which carries a lysine decarboxylase (AvbA) specific for siderophore synthesis, only one siderophore can be detected from many other Shewanella species. In this study, we examined a siderophore-overproducing mutant of Shewanella oneidensis which lacks an AvbA counterpart, and we found that it can also produce these three siderophores. We identified both SpeC and SpeF as promiscuous decarboxylases for both lysine and ornithine to synthesize the siderophore precursors cadaverine and putrescine, respectively. Intriguingly, putrescine is mainly synthesized from arginine through an arginine decarboxylation pathway in a constitutive manner, not liable to the concentrations of iron and siderophores. Our results provide further evidence that the substrate availability plays a determining role in siderophore production. Furthermore, we provide evidence to suggest that under iron starvation conditions, cells allocate more putrescine for siderophore biosynthesis by downregulating the expression of the enzyme that transforms putrescine into spermidine. Overall, this study provides another example of the great flexibility of bacterial metabolism that is honed by evolution to better fit living environments of these bacteria.IMPORTANCE The simultaneous production of multiple siderophores is considered a general strategy for microorganisms to rapidly adapt to their ever-changing environments. In this study, we show that some Shewanella spp. may downscale their capability for siderophore synthesis to facilitate adaptation. Although S. oneidensis lacks an enzyme specifically synthesizing cadaverine, it can produce it by using promiscuous ornithine decarboxylases. Despite this ability, this bacterium predominately produces the primary siderophore while restraining the production of secondary siderophores by regulating substrate availability. In addition to using the arginine decarboxylase (ADC) pathway for putrescine synthesis, cells optimize the putrescine pool for siderophore production. Our work provides an insight into the coordinated synthesis of multiple siderophores by harnessing promiscuous enzymes in bacteria and underscores the importance of substrate pools for the biosynthesis of natural products.


Assuntos
Shewanella/enzimologia , Sideróforos/biossíntese , Adaptação Fisiológica , Mutação , Shewanella/metabolismo
12.
Chemosphere ; 247: 125948, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32069723

RESUMO

The present study explores the rapid chlopyrifos (CPs) biodegradation potential of plant growth promoting (PGP) psychrophilic bacteria isolated from brackish water by enrichment culture technique. Based on biochemical tests and 16 S rDNA sequencing the isolate was identified as Shewanella sp. The isolate Shewanella BT05 showed significant growth rate in various concentrations of (10-50 mg/L) CPs. The isolate produced plant growth promoting factors, IAA (20.8 ± 1.2 and 15.4 ± 1.0 µg/mL) and siderophores (60.67 ± 1.2 and 57.5 ± 0.9%) in the absence and presence of CPs. Further, the isolate BT05 solublized phosphate (16.5 ± 1.0 and 12.0 ± 1.0 mm in size respectively), and produce hydrogen cyanide (excellent and moderate) in the presence and absence of CPs. The isolate BT05 degraded 94.3, 91.8, 87.9, 82.6, and 80.5% of CPs at 10, 20, 30, 40, and 50 mg/L, respectively, within 24 h. Further, the media conditions were optimized for enhanced CPs removal and observed 93% removal in the presence of 3.5% glucose in pH 7.0 at 32.5 °C. Fourier-transform infrared spectroscopy and high-performance liquid chromatography results indicated the role for Shewanella BT05 in the biomineralization of CPs. The results suggested the isolate BT05 could be used for CPs removal as well as PGP activity in contaminated soil.


Assuntos
Biodegradação Ambiental , Clorpirifos/metabolismo , Inseticidas/metabolismo , Shewanella/metabolismo , Praguicidas/análise , Praguicidas/metabolismo , Fosfatos/análise , Desenvolvimento Vegetal , Plantas/metabolismo , Shewanella/isolamento & purificação , Sideróforos/metabolismo , Microbiologia do Solo , Poluentes do Solo/análise , Poluentes do Solo/metabolismo
13.
Appl Microbiol Biotechnol ; 104(5): 2205-2216, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31927761

RESUMO

Cyclic diguanylate (c-di-GMP) is a second messenger involved in the regulation of various physiological processes in bacteria. However, its function in spoilage bacteria has not yet been addressed. Here, we studied the function of a tandem GGDEF-EAL domain protein, Sbal_3235, in the spoilage bacterium Shewanella baltica OS155. The deletion of sbal_3235 significantly reduced the c-di-GMP level, biofilm formation, and exopolysaccharide, trimethylamine (TMA), and putrescine production; sbal_3235 deletion also downregulated the expression of the torS and speF genes and affected membrane fatty acid composition. Site-directed mutagenesis in conserved GGDEF and EAL motifs abolished diguanylate cyclase (DGC) and phosphodiesterase (PDE) activity, respectively. These data indicate that Sbal_3235 is an essential contributor to the c-di-GMP pool with bifunctional DGC and PDE activity, which is involved in the biofilm formation and spoilage activity of S. baltica OS155. Our findings expand the biochemical role of c-di-GMP and uncover its link to spoilage activities, providing novel targets for food quality and safety controlling.


Assuntos
Proteínas de Bactérias/metabolismo , GMP Cíclico/análogos & derivados , Shewanella/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Biofilmes , GMP Cíclico/metabolismo , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Ácidos Graxos/química , Ácidos Graxos/metabolismo , Regulação Bacteriana da Expressão Gênica , Fósforo-Oxigênio Liases/genética , Fósforo-Oxigênio Liases/metabolismo , Domínios Proteicos , Shewanella/química , Shewanella/genética
14.
Sci Rep ; 10(1): 953, 2020 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-31969587

RESUMO

Shewanella oneidensis, a metal reducer and facultative anaerobe, expresses a large number of c-type cytochromes, many of which function as anaerobic reductases. All of these proteins contain the typical heme-binding motif CXXCH and require the Ccm proteins for maturation. Two c-type cytochrome reductases also possess atypical heme-binding sites, the NrfA nitrite reductase (CXXCK) and the SirA sulfite reductase (CX12NKGCH). S. oneidensis MR-1 encodes two cytochrome c synthetases (CcmF and SirE) and two apocytochrome c chaperones (CcmI and SirG). SirE located in the sir gene cluster is required for the maturation of SirA, but not NrfA. Here we show that maturation of SirA requires the combined function of the two apocytochrome c chaperones CcmI and SirG. Loss of either protein resulted in decreased sulfite reductase. Furthermore, SirA was not detected in a mutant that lacked both chaperones, perhaps due to misfolding or instability. These results suggest that CcmI interacts with SirEFG during SirA maturation, and with CcmF during maturation of NrfA. Additionally, we show that CRP regulates expression of sirA via the newly identified transcriptional regulatory protein, SirR.


Assuntos
Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Shewanella/metabolismo , Sulfito Redutase (NADPH)/metabolismo , Proteínas de Bactérias/genética , Nitrito Redutases/genética , Nitrito Redutases/metabolismo , Shewanella/genética , Sulfito Redutase (NADPH)/genética
15.
Chemosphere ; 247: 125902, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31978657

RESUMO

Microorganisms, iron minerals, and humic acid are widely common in the soil and water environment and closely interact within environmental processes. In this study, the Cr(VI) removal by Shewanella oneidensis MR-1 (S. oneidensis) was examined in the presence of goethite and humic acid (HA) to mimic the real environment situation. Scanning electron microscopy (SEM) combined with energy disperse spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) technologies were used to probe the Cr(VI) reduction mechanism. Our results showed that S. oneidensis alone could reduce 65% of 1.0 mM Cr(VI) after 8 h of the reduction process. Meanwhile, Cr(VI) reduction rate was declined to 56% in the presence of goethite or humic acid. Contrary, the Cr(VI) reduction rate was mightily increased to 79% by the ternary complex of S. oneidensis-goethite-HA where reduced humic acid (HAred) acted as electron shuttles and diminished the bacterial adhesion to the goethite surface thereby enhanced electron transfer and increased the extent of Cr(VI) reduction by 1.3 fold. XPS analysis indicated that Cr(VI) was reduced to Cr(III), and the final yields were Cr(OH)3 and Cr2O3 precipitated on the surface of bacterial cells. S. oneidensis could also reduce Fe(III) in goethite to Fe(II), which in turn reduced Cr(VI). These results suggested that iron mineral-humic acid complex could enhance the microbial reduction of Cr(VI) and revealed the promotion role of HA in the Cr(VI) bioreduction process. This study affords inclusive insights on the Cr(VI) reduction kinetics and mechanisms in the most complicated systems.


Assuntos
Biodegradação Ambiental , Cromo/metabolismo , Shewanella/metabolismo , Cromo/química , Transporte de Elétrons , Elétrons , Substâncias Húmicas , Ferro/química , Compostos de Ferro , Minerais/química , Oxirredução , Solo
16.
Chemosphere ; 246: 125681, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31896014

RESUMO

Tetracycline (TC) as an emerging contaminant has raised serious concerns about its toxicity and removal in wastewater treatment processes. The more toxic transformation products of TC, 4-epitetracycline (ETC), anhydrotetracycline (ATC) and 4-epianhydrotetracycline (EATC) are also widely detected. This study investigated the antibacterial and bactericidal activity of TC, ETC, ATC, EATC against Shewanella sp, using Escherichia coli and Pseudomonas aeruginosa strains as quality controls. Further, batch assays were conducted to investigate the inhibition of these antibiotics on the phosphorus removal of the Shewanella strain, and removal mechanisms of TC and its transformation products (TCs). The inhibition on phosphorus removal by the Shewanella strain at 20 mg L-1 was in the order of ATC > EATC > TC > ETC. COD removal, poly-P accumulation and glycogen synthesis by the Shewanella strain were also inhibited. Biodegradation was the main removal mechanism of TC and ETC, while adsorption was the main one of ATC and EATC. This study helps to further understand the structure-activity relationship of TC.


Assuntos
Antibacterianos/toxicidade , Fósforo/metabolismo , Shewanella/efeitos dos fármacos , Tetraciclina/toxicidade , Adsorção , Compostos Heterocíclicos , Shewanella/metabolismo , Tetraciclina/análise , Tetraciclinas/análise , Águas Residuárias
17.
Proteins ; 88(1): 196-205, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31344265

RESUMO

Shewanella oneidensis MR-1 shows remarkable respiratory versatility with a large variety of extracellular electron acceptors (termed extracellular electron transfer, EET). To utilize the various electron acceptors, the bacterium must employ complex regulatory mechanisms to elicit the relevant EET pathways. To investigate the relevant mechanisms, we integrated EET genes and related transcriptional factors (TFs) into transcriptional regulatory modules (TRMs) and showed that many bridge proteins in these modules were signal proteins, which generally contained one or more signal processing domains (eg, GGDEF, EAL, PAS, etc.). Since Shewanella has to respond to diverse environmental conditions despite encoding few EET-relevant TFs, the overabundant signal proteins involved in the TRMs can help decipher the mechanism by which these microbes elicit a wide range of condition-specific responses. By combining proteomic data and protein bioinformatic analysis, we demonstrated that diverse signal proteins reconciled the different EET pathways, and we discussed the functional roles of signal proteins involved in the well-known MtrCAB pathway. Additionally, we showed that the signal proteins SO_2145 and SO_1417 played central roles in triggering EET pathways in anaerobic environments. Taken together, our results suggest that signal proteins have a profound impact on the transcriptional regulation of EET genes and thus have potential applications in microbial fuel cells.


Assuntos
Proteínas de Bactérias/genética , Regulação Bacteriana da Expressão Gênica , Shewanella/genética , Fatores de Transcrição/genética , Proteínas de Bactérias/metabolismo , Transporte de Elétrons , Redes Reguladoras de Genes , Mapas de Interação de Proteínas , Shewanella/metabolismo , Transdução de Sinais , Fatores de Transcrição/metabolismo , Ativação Transcricional
18.
Genomics ; 112(1): 736-748, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31095997

RESUMO

Shewanella baltica 128 is a specific spoilage organism (SSO) isolated from the refrigerated shrimp that results in shrimp spoilage. This study reported the complete genome sequencing of this strain, with the primary annotations associated with amino acid transport and metabolism (8.66%), indicating that S. baltica 128 has good potential for degrading proteins. In vitro experiments revealed Shewanella baltica 128 could adapt to the stress conditions by regulating its growth and biofilm formation. Genes that related to the spoilage-related metabolic pathways, including trimethylamine metabolism (torT), sulfur metabolism (cysM), putrescine metabolism (speC), biofilm formation (rpoS) and serine protease production (degS), were identified. Genes (LuxS, pfs, LuxR and qseC) that related to the specific QS system were also identified. Complete genome sequence of S. baltica 128 provide insights into the QS-related spoilage potential, which might provide novel information for the development of new approaches for spoilage detection and prevention based on QS target.


Assuntos
Adaptação Fisiológica/genética , Genes Bacterianos , Loci Gênicos , Percepção de Quorum/genética , Alimentos Marinhos/microbiologia , Shewanella , Microbiologia de Alimentos , Shewanella/genética , Shewanella/isolamento & purificação , Shewanella/metabolismo
19.
Environ Geochem Health ; 42(8): 2547-2556, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31858357

RESUMO

Uranium is a contaminant of major concern across the US Department of Energy complex that served a leading role in nuclear weapon fabrication for half a century. In an effort to decrease the concentration of soluble uranium, tripolyphosphate injections were identified as a feasible remediation strategy for sequestering uranium in situ in contaminated groundwater at the Hanford Site. The introduction of sodium tripolyphosphate into uranium-bearing porous media results in the formation of uranyl phosphate minerals (autunite) of general formula {X1-2[(UO2)(PO4)]2-1·nH2O}, where X is a monovalent or divalent cation. The stability of the uranyl phosphate minerals is a critical factor that determines the long-term effectiveness of this remediation strategy that can be affected by biogeochemical factors such as the presence of bicarbonates and bacterial activity. The objective of this research was to investigate the effect of bicarbonate ions present in the aqueous phase on Ca-autunite dissolution under anaerobic conditions, as well as the role of metal-reducing facultative bacterium Shewanella oneidensis MR1. The concentration of total uranium determined in the aqueous phase was in direct correlation to the concentration of bicarbonate present in the solution, and the release of Ca, U and P into the aqueous phase was non-stoichiometric. Experiments revealed the absence of an extensive biofilm on autunite surface, while thermodynamic modeling predicted the presence of secondary minerals, which were identified through microscopy. In conclusion, the dissolution of autunite under the conditions studied is susceptible to bicarbonate concentration, as well as microbial presence.


Assuntos
Bicarbonatos/química , Shewanella/metabolismo , Urânio/química , Anaerobiose , Água Subterrânea , Minerais/química , Minerais/metabolismo , Fosfatos/química , Fosfatos/metabolismo , Polifosfatos , Solubilidade , Termodinâmica , Urânio/metabolismo , Compostos de Urânio/química , Compostos de Urânio/metabolismo , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo
20.
Microb Cell Fact ; 18(1): 216, 2019 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-31870378

RESUMO

This study reveals that it is possible to secrete truncated versions of outer membrane cytochromes into the culture supernatant and that these proteins can provide a basis for the export of heterologously produced proteins. Different soluble and truncated versions of the outer membrane cytochrome MtrF were analyzed for their suitability to be secreted. A protein version with a very short truncation of the N-terminus to remove the recognition sequence for the addition of a lipid anchor is secreted efficiently to the culture supernatant, and moreover this protein could be further truncated by a deletion of 160 amino acid and still is detectable in the supernatant. By coupling a cellulase to this soluble outer membrane cytochrome, the export efficiency was measured by means of relative cellulase activity. We conclude that outer membrane cytochromes of S. oneidensis can be applied as transporters for the export of target proteins into the medium using the type II secretion pathway.


Assuntos
Proteínas da Membrana Bacteriana Externa/biossíntese , Membrana Externa Bacteriana/metabolismo , Citocromos/metabolismo , Shewanella/metabolismo , Shewanella/química , Solubilidade
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