scholarly journals Microfluidic dielectrophoresis illuminates the relationship between microbial cell envelope polarizability and electrochemical activity

2019 ◽  
Vol 5 (1) ◽  
pp. eaat5664 ◽  
Author(s):  
Qianru Wang ◽  
A.-Andrew D. Jones ◽  
Jeffrey A. Gralnick ◽  
Liwei Lin ◽  
Cullen R. Buie
Keyword(s):  
Environmental Remediation ◽  
Cell Envelope ◽  
Shewanella Oneidensis ◽  
Growth Conditions ◽  
Geobacter Sulfurreducens ◽  
Rapid Screening ◽  
Extracellular Electron Transfer ◽  
Insoluble Electron Acceptors ◽  
The Relationship ◽  
Type Strains

Electrons can be transported from microbes to external insoluble electron acceptors (e.g., metal oxides or electrodes in an electrochemical cell). This process is known as extracellular electron transfer (EET) and has received considerable attention due to its applications in environmental remediation and energy conversion. However, the paucity of rapid and noninvasive phenotyping techniques hinders a detailed understanding of microbial EET mechanisms. Most EET phenotyping techniques assess microorganisms based on their metabolism and growth in various conditions and/or performance in electrochemical systems, which requires large sample volumes and cumbersome experimentation. Here, we use microfluidic dielectrophoresis to show a strong correlation between bacterial EET and surface polarizability. We analyzed surface polarizabilities for wild-type strains and cytochrome-deletion mutants of two model EET microbes,Geobacter sulfurreducensandShewanella oneidensis, and forEscherichia colistrains heterologously expressingS. oneidensisEET pathways in various growth conditions. Dielectrophoretic phenotyping is achieved with small cell culture volumes (~100 μl) in a short amount of time (1 to 2 min per strain). Our work demonstrates that cell polarizability is diminished in response to deletions of crucial outer-membrane cytochromes and enhanced due to additions of EET pathways. Results of this work hold exciting promise for rapid screening of direct EET or other cell envelope phenotypes using cell polarizability as a proxy, especially for microbes difficult to cultivate in laboratory conditions.

scholarly journals GEMM-I riboswitches from Geobacter sense the bacterial second messenger cyclic AMP-GMP

2015 ◽  
Vol 112 (17) ◽  
pp. 5383-5388 ◽  
Author(s):  
Colleen A. Kellenberger ◽  
Stephen C. Wilson ◽  
Scott F. Hickey ◽  
Tania L. Gonzalez ◽  
Yichi Su ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Cell Biology ◽  
Environmental Remediation ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Bacterial Physiology ◽  
Fluorescent Biosensor ◽  
Environmental Bacterium ◽  
Cyclic Dinucleotides ◽  
And Function

Cyclic dinucleotides are an expanding class of signaling molecules that control many aspects of bacterial physiology. A synthase for cyclic AMP-GMP (cAG, also referenced as 3′-5′, 3′-5′ cGAMP) called DncV is associated with hyperinfectivity of Vibrio cholerae but has not been found in many bacteria, raising questions about the prevalence and function of cAG signaling. We have discovered that the environmental bacterium Geobacter sulfurreducens produces cAG and uses a subset of GEMM-I class riboswitches (GEMM-Ib, Genes for the Environment, Membranes, and Motility) as specific receptors for cAG. GEMM-Ib riboswitches regulate genes associated with extracellular electron transfer; thus cAG signaling may control aspects of bacterial electrophysiology. These findings expand the role of cAG beyond organisms that harbor DncV and beyond pathogenesis to microbial geochemistry, which is important to environmental remediation and microbial fuel cell development. Finally, we have developed an RNA-based fluorescent biosensor for live-cell imaging of cAG. This selective, genetically encodable biosensor will be useful to probe the biochemistry and cell biology of cAG signaling in diverse bacteria.

scholarly journals Extracellular Electron Transfer: Respiratory or Nutrient Homeostasis?

2020 ◽  
Vol 202 (7) ◽  
Author(s):  
Lars J. C. Jeuken ◽  
Kiel Hards ◽  
Yoshio Nakatani
Keyword(s):  
Electron Transfer ◽  
Iron Reduction ◽  
Ferric Iron ◽  
Shewanella Oneidensis ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Gram Positive ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Nutrient Homeostasis

ABSTRACT Exoelectrogens are able to transfer electrons extracellularly, enabling them to respire on insoluble terminal electron acceptors. Extensively studied exoelectrogens, such as Geobacter sulfurreducens and Shewanella oneidensis, are Gram negative. More recently, it has been reported that Gram-positive bacteria, such as Listeria monocytogenes and Enterococcus faecalis, also exhibit the ability to transfer electrons extracellularly, although it is still unclear whether this has a function in respiration or in redox control of the environment, for instance, by reducing ferric iron for iron uptake. In this issue of Journal of Bacteriology, Hederstedt and colleagues report on experiments that directly compare extracellular electron transfer (EET) pathways for ferric iron reduction and respiration and find a clear difference (L. Hederstedt, L. Gorton, and G. Pankratova, J Bacteriol 202:e00725-19, 2020, https://doi.org/10.1128/JB.00725-19), providing further insights and new questions into the function and metabolic pathways of EET in Gram-positive bacteria.

Mtr extracellular electron-transfer pathways in Fe(III)-reducing or Fe(II)-oxidizing bacteria: a genomic perspective

2012 ◽  
Vol 40 (6) ◽  
pp. 1261-1267 ◽  
Author(s):  
Liang Shi ◽  
Kevin M. Rosso ◽  
John M. Zachara ◽  
James K. Fredrickson
Keyword(s):  
Electron Transfer ◽  
Cell Envelope ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Bacterial Cells ◽  
Electron Transfer Pathway ◽  
Protein Components ◽  
Micro Organisms ◽  
Reducing Bacteria ◽  
Mediate Electron Transfer

Originally discovered in the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), key components of the Mtr (i.e. metal-reducing) pathway exist in all strains of metal-reducing Shewanella characterized. The protein components identified to date for the Mtr pathway of MR-1 include four multihaem c-Cyts (c-type cytochromes), CymA, MtrA, MtrC and OmcA, and a porin-like outer membrane protein MtrB. They are strategically positioned along the width of the MR-1 cell envelope to mediate electron transfer from the quinone/quinol pool in the inner membrane to Fe(III)-containing minerals external to the bacterial cells. A survey of microbial genomes has identified homologues of the Mtr pathway in other dissimilatory Fe(III)-reducing bacteria, including Aeromonas hydrophila, Ferrimonas balearica and Rhodoferax ferrireducens, and in the Fe(II)-oxidizing bacteria Dechloromonas aromatica RCB, Gallionella capsiferriformans ES-2 and Sideroxydans lithotrophicus ES-1. The apparent widespread distribution of Mtr pathways in both Fe(III)-reducing and Fe(II)-oxidizing bacteria suggests a bidirectional electron transfer role, and emphasizes the importance of this type of extracellular electron-transfer pathway in microbial redox transformation of iron. The organizational and electron-transfer characteristics of the Mtr pathways may be shared by other pathways used by micro-organisms for exchanging electrons with their extracellular environments.

NETWORK ANALYSIS OF COMMON DIFFERENTIAL GENES IDENTIFIES KEY GENES AND IMPORTANT MODULES UNDERLYING EXTRACELLULAR ELECTRON TRANSFER PROCESSES

2019 ◽  
Vol 27 (01) ◽  
pp. 51-67
Author(s):  
DEWU DING
Keyword(s):  
Electron Transfer ◽  
Network Analysis ◽  
Molecular Mechanisms ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Ppi Network ◽  
Protein Protein Interaction ◽  
New Genes ◽  
Electron Transfer Processes ◽  
Insoluble Electron Acceptors

Electricigens can transfer electrons that produced in intracellular metabolic processes to cellular surface to restore extracellular insoluble electron acceptors (extracellular electron transfer, EET). To uncover the molecular mechanisms underlying EET processes, we integrated transcriptome changes accompanying such processes with molecular network. Firstly, time-series expression datasets for Shewanella oneidensis MR-1 under limited/changed [Formula: see text] conditions were obtained from the GEO database, and a total of 336 common differentially expressed genes (DEGs) were identified. Then, we constructed the protein–protein interaction (PPI) network that involved in EET processes from these DEGs. Furthermore, by using centralization analysis and community detection, network analysis of the PPI network was performed. Although the fundamental EET genes are similar to previous studies, important new genes have been discovered. Taking together, our study identified many literature-validated genes critical to EET processes, and also proposed some novel genes that were putatively involved in EET processes.

scholarly journals Geobacter sulfurreducensextracellular multiheme cytochrome PgcA facilitates respiration to Fe(III) oxides but not electrodes

2017 ◽  
Author(s):  
Lori Zacharoff ◽  
Dana Morrone ◽  
Daniel R. Bond
Keyword(s):  
Electron Transfer ◽  
Metal Oxides ◽  
Solid Phase ◽  
Shewanella Oneidensis ◽  
Helical Structure ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Mineral Surfaces ◽  
Electrode Surfaces ◽  
Multiheme Cytochrome

AbstractExtracellular cytochromes are hypothesized to facilitate the final steps of electron transfer between the outer membrane of the metal-reducing bacteriumGeobacter sulfurreducensand solid-phase electron acceptors such as metal oxides and electrode surfaces during the course of respiration. The trihemec-type cytochrome PgcA exists in the extracellular space ofG. sulfurreducens, and is one of many multihemec-type cytochromes known to be loosely bound to the bacterial outer surface. Deletion ofpgcAusing a markerless method resulted in mutants unable to transfer electrons to Fe(III) and Mn(IV) oxides; yet the same mutants maintained the ability to respire electrode surfaces and soluble Fe(III) citrate. When expressed and purified fromShewanella oneidensis, PgcA demonstrated a primarily alpha helical structure, three bound hemes, and was processed into a shorter 41 kDa form lacking the lipodomain. Purified PgcA bound Fe(III) oxides, but not magnetite, and when PgcA was added to cell suspensions ofG. sulfurreducens,PgcA accelerated Fe(III) reduction similar to addition of FMN. Addition of soluble PgcA to ∆pgcAmutants also restored Fe(III) reduction. This report highlights a distinction between proteins involved in extracellular electron transfer to metal oxides and poised electrodes, and suggests a specific role for PgcA in facilitating electron transfer at mineral surfaces.

scholarly journals Divergent Nrf Family Proteins and MtrCAB Homologs Facilitate Extracellular Electron Transfer inAeromonas hydrophila

2018 ◽  
Vol 84 (23) ◽  
Author(s):  
Bridget E. Conley ◽  
Peter J. Intile ◽  
Daniel R. Bond ◽  
Jeffrey A. Gralnick
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Aeromonas Hydrophila ◽  
Shewanella Oneidensis ◽  
Geobacter Sulfurreducens ◽  
Model Systems ◽  
Extracellular Electron Transfer ◽  
Metal Reduction ◽  
Inner Membrane ◽  
Content Type

ABSTRACTExtracellular electron transfer (EET) is a strategy for respiration in which electrons generated from metabolism are moved outside the cell to a terminal electron acceptor, such as iron or manganese oxide. EET has primarily been studied in two model systems,Shewanella oneidensisandGeobacter sulfurreducens. Metal reduction has also been reported in numerous microorganisms, includingAeromonasspp., which are ubiquitousGammaproteobacteriafound in aquatic ecosystems, with some species capable of pathogenesis in humans and fish. Genomic comparisons ofAeromonasspp. revealed a potential outer membrane conduit homologous toS. oneidensisMtrCAB. While the ability to respire metals and mineral oxides is not widespread in the genusAeromonas, 90% of the sequencedAeromonas hydrophilaisolates contain MtrCAB homologs.A. hydrophilaATCC 7966 mutants lackingmtrAare unable to reduce metals. Expression ofA. hydrophila mtrCABin anS. oneidensismutant lacking homologous components restored metal reduction. Although the outer membrane conduits for metal reduction were similar, homologs of theS. oneidensisinner membrane and periplasmic EET components CymA, FccA, and CctA were not found inA. hydrophila. We characterized a cluster of genes predicted to encode components related to a formate-dependent nitrite reductase (NrfBCD), here named NetBCD (forNrf-likeelectrontransfer), and a predicted diheme periplasmic cytochrome, PdsA (periplasmicdihemeshuttle). We present genetic evidence that proteins encoded by this cluster facilitate electron transfer from the cytoplasmic membrane across the periplasm to the MtrCAB conduit and function independently from an authentic NrfABCD system.A. hydrophilamutants lackingpdsAandnetBCDwere unable to reduce metals, while heterologous expression of these genes could restore metal reduction in anS. oneidensismutant background. EET may therefore allowA. hydrophilaand other species ofAeromonasto persist and thrive in iron- or manganese-rich oxygen-limited environments.IMPORTANCEMetal-reducing microorganisms are used for electricity production, bioremediation of toxic compounds, wastewater treatment, and production of valuable compounds. Despite numerous microorganisms being reported to reduce metals, the molecular mechanism has primarily been studied in two model systems,Shewanella oneidensisandGeobacter sulfurreducens. We have characterized the mechanism of extracellular electron transfer inAeromonas hydrophila, which uses the well-studiedShewanellasystem, MtrCAB, to move electrons across the outer membrane; however, mostAeromonasspp. appear to use a novel mechanism to transfer electrons from the inner membrane through the periplasm and to the outer membrane. The conserved use of MtrCAB inShewanellaspp. andAeromonasspp. for metal reduction and conserved genomic architecture of metal reduction genes inAeromonasspp. may serve as genomic markers for identifying metal-reducing microorganisms from genomic or transcriptomic sequencing. Understanding the variety of pathways used to reduce metals can allow for optimization and more efficient design of microorganisms used for practical applications.

scholarly journals Tuning Redox Potential of Anthraquinone-2-Sulfonate (AQS) by Chemical Modification to Facilitate Electron Transfer From Electrodes in Shewanella oneidensis

2021 ◽  
Vol 9 ◽  
Author(s):  
Ning Xu ◽  
Tai-Lin Wang ◽  
Wen-Jie Li ◽  
Yan Wang ◽  
Jie-Jie Chen ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Redox Potential ◽  
Environmental Remediation ◽  
Rational Design ◽  
Coulombic Efficiency ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Total Charge ◽  
Redox Potentials ◽  
Chemical Production

Bioelectrochemical systems (BESs) are emerging as attractive routes for sustainable energy generation, environmental remediation, bio-based chemical production and beyond. Electron shuttles (ESs) can be reversibly oxidized and reduced among multiple redox reactions, thereby assisting extracellular electron transfer (EET) process in BESs. Here, we explored the effects of 14 ESs on EET in Shewanella oneidensis MR-1, and found that anthraquinone-2-sulfonate (AQS) led to the highest cathodic current density, total charge production and reduction product formation. Subsequently, we showed that the introduction of -OH or -NH2 group into AQS at position one obviously affected redox potentials. The AQS-1-NH2 exhibited a lower redox potential and a higher Coulombic efficiency compared to AQS, revealing that the ESs with a more negative potential are conducive to minimize energy losses and improve the reduction of electron acceptor. Additionally, the cytochromes MtrA and MtrB were required for optimal AQS-mediated EET of S. oneidensis MR-1. This study will provide new clues for rational design of efficient ESs in microbial electrosynthesis.

scholarly journals Isolation of a gene required for programmed initiation of development by Aspergillus nidulans.

1992 ◽  
Vol 12 (9) ◽  
pp. 3827-3833 ◽  
Author(s):  
T H Adams ◽  
W A Hide ◽  
L N Yager ◽  
B N Lee
Keyword(s):  
Life Cycle ◽  
Aspergillus Nidulans ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Nutrient Deprivation ◽  
Deletion Mutants ◽  
Wild Type ◽  
Microbial Development ◽  
Type Strains ◽  
Posttranscriptional Level

In contrast to many other cases in microbial development, Aspergillus nidulans conidiophore production initiates primarily as a programmed part of the life cycle rather than as a response to nutrient deprivation. Mutations in the acoD locus result in "fluffy" colonies that appear to grow faster than the wild type and proliferate as undifferentiated masses of vegetative cells. We show that unlike wild-type strains, acoD deletion mutants are unable to make conidiophores under optimal growth conditions but can be induced to conidiate when growth is nutritionally limited. The requirement for acoD in conidiophore development occurs prior to activation of brlA, a primary regulator of development. The acoD transcript is present both in vegetative hyphae prior to developmental induction and in developing cultures. However, the effects of acoD mutations are detectable only after developmental induction. We propose that acoD activity is primarily controlled at the posttranscriptional level and that it is required to direct developmentally specific changes that bring about growth inhibition and activation of brlA expression to result in conidiophore development.

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