scholarly journals Comparative insights into genome signatures of ferric iron oxide- and anode-stimulated Desulfuromonas spp. strains

BMC Genomics ◽  
2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Yong Guo ◽  
Tomo Aoyagi ◽  
Tomoyuki Hori
Keyword(s):  
Iron Oxide ◽  
Genome Rearrangement ◽  
Ferric Iron ◽  
Electron Acceptors ◽  
Extracellular Electron Transfer ◽  
Redox Potentials ◽  
Bacterial Strains ◽  
Biosynthesis Gene Cluster ◽  
Genomic Signatures ◽  
Flagellar Biosynthesis

Abstract Background Halotolerant Fe (III) oxide reducers affiliated in the family Desulfuromonadaceae are ubiquitous and drive the carbon, nitrogen, sulfur and metal cycles in marine subsurface sediment. Due to their possible application in bioremediation and bioelectrochemical engineering, some of phylogenetically close Desulfuromonas spp. strains have been isolated through enrichment with crystalline Fe (III) oxide and anode. The strains isolated using electron acceptors with distinct redox potentials may have different abilities, for instance, of extracellular electron transport, surface recognition and colonization. The objective of this study was to identify the different genomic signatures between the crystalline Fe (III) oxide-stimulated strain AOP6 and the anode-stimulated strains WTL and DDH964 by comparative genome analysis. Results The AOP6 genome possessed the flagellar biosynthesis gene cluster, as well as diverse and abundant genes involved in chemotaxis sensory systems and c-type cytochromes capable of reduction of electron acceptors with low redox potentials. The WTL and DDH964 genomes lacked the flagellar biosynthesis cluster and exhibited a massive expansion of transposable gene elements that might mediate genome rearrangement, while they were deficient in some of the chemotaxis and cytochrome genes and included the genes for oxygen resistance. Conclusions Our results revealed the genomic signatures distinctive for the ferric iron oxide- and anode-stimulated Desulfuromonas spp. strains. These findings highlighted the different metabolic abilities, such as extracellular electron transfer and environmental stress resistance, of these phylogenetically close bacterial strains, casting light on genome evolution of the subsurface Fe (III) oxide reducers.

scholarly journals An Inner Membrane Cytochrome Required Only for Reduction of High Redox Potential Extracellular Electron Acceptors

mBio ◽  
2014 ◽  
Vol 5 (6) ◽  
Author(s):  
Caleb E. Levar ◽  
Chi Ho Chan ◽  
Misha G. Mehta-Kolte ◽  
Daniel R. Bond
Keyword(s):  
Electron Transfer ◽  
Electron Acceptors ◽  
Geobacter Sulfurreducens ◽  
Extracellular Electron Transfer ◽  
Redox Potentials ◽  
Inner Membrane ◽  
Content Type ◽  
Transfer Strategies ◽  
Reducing Bacteria ◽  
Metal Reducing Bacteria

ABSTRACTDissimilatory metal-reducing bacteria, such asGeobacter sulfurreducens, transfer electrons beyond their outer membranes to Fe(III) and Mn(IV) oxides, heavy metals, and electrodes in electrochemical devices. In the environment, metal acceptors exist in multiple chelated and insoluble forms that span a range of redox potentials and offer different amounts of available energy. Despite this, metal-reducing bacteria have not been shown to alter their electron transfer strategies to take advantage of these energy differences. Disruption ofimcH, encoding an inner membranec-type cytochrome, eliminated the ability ofG. sulfurreducensto reduce Fe(III) citrate, Fe(III)-EDTA, and insoluble Mn(IV) oxides, electron acceptors with potentials greater than 0.1 V versus the standard hydrogen electrode (SHE), but theimcHmutant retained the ability to reduce Fe(III) oxides with potentials of ≤−0.1 V versus SHE. TheimcHmutant failed to grow on electrodes poised at +0.24 V versus SHE, but switching electrodes to −0.1 V versus SHE triggered exponential growth. At potentials of ≤−0.1 V versus SHE, both the wild type and theimcHmutant doubled 60% slower than at higher potentials. Electrodes poised even 100 mV higher (0.0 V versus SHE) could not triggerimcHmutant growth. These results demonstrate thatG. sulfurreducenspossesses multiple respiratory pathways, that some of these pathways are in operation only after exposure to low redox potentials, and that electron flow can be coupled to generation of different amounts of energy for growth. The redox potentials that trigger these behaviors mirror those of metal acceptors common in subsurface environments whereGeobacteris found.IMPORTANCEInsoluble metal oxides in the environment represent a common and vast reservoir of energy for respiratory microbes capable of transferring electrons across their insulating membranes to external acceptors, a process termed extracellular electron transfer. Despite the global biogeochemical importance of metal cycling and the ability of such organisms to produce electricity at electrodes, fundamental gaps in the understanding of extracellular electron transfer biochemistry exist. Here, we describe a conserved inner membrane redox protein inGeobacter sulfurreducenswhich is required only for electron transfer to high-potential compounds, and we show thatG. sulfurreducenshas the ability to utilize different electron transfer pathways in response to the amount of energy available in a metal or electrode distant from the cell.

scholarly journals Phenazines and Other Redox-Active Antibiotics Promote Microbial Mineral Reduction

2004 ◽  
Vol 70 (2) ◽  
pp. 921-928 ◽  
Author(s):  
Maria E. Hernandez ◽  
Andreas Kappler ◽  
Dianne K. Newman
Keyword(s):  
Natural Products ◽  
Manganese Oxides ◽  
Ferric Iron ◽  
Shewanella Oneidensis ◽  
Iron Chelator ◽  
Redox Potentials ◽  
Bacterial Strains ◽  
Redox Active ◽  
Therapeutic Properties ◽  
Iron And Manganese

ABSTRACT Natural products with important therapeutic properties are known to be produced by a variety of soil bacteria, yet the ecological function of these compounds is not well understood. Here we show that phenazines and other redox-active antibiotics can promote microbial mineral reduction. Pseudomonas chlororaphis PCL1391, a root isolate that produces phenazine-1-carboxamide (PCN), is able to reductively dissolve poorly crystalline iron and manganese oxides, whereas a strain carrying a mutation in one of the phenazine-biosynthetic genes (phzB) is not; the addition of purified PCN restores this ability to the mutant strain. The small amount of PCN produced relative to the large amount of ferric iron reduced in cultures of P. chlororaphis implies that PCN is recycled multiple times; moreover, poorly crystalline iron (hydr)oxide can be reduced abiotically by reduced PCN. This ability suggests that PCN functions as an electron shuttle rather than an iron chelator, a finding that is consistent with the observation that dissolved ferric iron is undetectable in culture fluids. Multiple phenazines and the glycopeptidic antibiotic bleomycin can also stimulate mineral reduction by the dissimilatory iron-reducing bacterium Shewanella oneidensis MR1. Because diverse bacterial strains that cannot grow on iron can reduce phenazines, and because thermodynamic calculations suggest that phenazines have lower redox potentials than those of poorly crystalline iron (hydr)oxides in a range of relevant environmental pH (5 to 9), we suggest that natural products like phenazines may promote microbial mineral reduction in the environment.

scholarly journals Isolation and characterization of electrochemically active subsurface Delftia and Azonexus species

2016 ◽  
Author(s):  
Yamini Jangir ◽  
Sarah French ◽  
Lily M. Momper ◽  
Duane P. Moser ◽  
Jan P. Amend ◽  
...  
Keyword(s):  
Fractured Rock ◽  
Synthetic Medium ◽  
Electrochemical Techniques ◽  
Electron Acceptors ◽  
Extracellular Electron Transfer ◽  
Total Protein Content ◽  
Redox Potentials ◽  
Electrode Surfaces ◽  
Isolation And Characterization ◽  
Fractured Rock Aquifer

AbstractContinental subsurface environments can present significant energetic challenges to the resident microorganisms. While these environments are geologically diverse, potentially allowing energy harvesting by microorganisms that catalyze redox reactions, many of the abundant electron donors and acceptors are insoluble and therefore not directly bioavailable. Extracellular electron transfer (EET) is a metabolic strategy that microorganisms can deploy to meet the challenges of interacting with redox-active surfaces. Though mechanistically characterized in a few metal-reducing bacteria, the role, extent, and diversity of EET in subsurface ecosystems remains unclear. Since this process can be mimicked on electrode surfaces, it opens the door to electrochemical techniques to enrich for and quantify the activities of environmental microorganismsin situ. Here, we report the electrochemical enrichment of microorganisms from a deep fractured-rock aquifer in Death Valley, California, USA. In experiments performed in mesocosms containing a synthetic medium based on aquifer chemistry, four working electrodes were poised at different redox potentials (272, 373, 472, 572 mV vs. SHE) to serve as electron acceptors, resulting in anodic currents coupled to the oxidation of acetate during enrichment. The anodes were dominated byBetaproteobacteriafrom the familiesComamonadaceaeandRhodocyclaceae.A representative of each dominant family was subsequently isolated from electrode-associated biomass. The EET abilities of the isolatedDelftiastrain (designated WE1–13) andAzonexusstrain (designated WE2–4) were confirmed in electrochemical reactors using working electrodes poised at 522 mV vs. SHE. The rise in anodic current upon inoculation was correlated with a modest increase in total protein content. Both genera have been previously observed in mixed communities of microbial fuel cell enrichments, but this is the first direct measurement of their electrochemical activity. While alternate metabolisms (e.g. nitrate reduction) by these organisms were previously known, our observations suggest that additional ‘hidden’ interactions with external electron acceptors are also possible. Electrochemical approaches are well positioned to dissect such extracellular interactions that may be prevalent in the subsurface.

Dicyano-bis(pyridin-2,6-dicarbothioato)-ferrat (II)/ferrat (III), ein weiteres eisenhaltiges Redoxsystem aus der Kulturlösung eines Pseudomonas-Stammes [1] / Dicyano-bis(pyridin-2,6-dicarbothioato)-ferrate (II)/ferrate (III), a Further Fe Containing Redox System from the Culture Medium of Pseudomonas sp.

1985 ◽  
Vol 40 (3-4) ◽  
pp. 201-207 ◽  
Author(s):  
U. Hildebrand ◽  
K. Taraz ◽  
H. Budzikiewicz ◽  
H. Korth ◽  
G. Pulverer
Keyword(s):  
Pseudomonas Putida ◽  
Culture Medium ◽  
Redox System ◽  
Pseudomonas Sp ◽  
Redox Potentials ◽  
Bacterial Strains ◽  
Normal Potential

From the culture medium of Pseudomonas sp. a further Fe containing complex, viz. dicyano- bis(pyridin-2,6-dicarbothioato)-ferrate (III) (2) has been isolated which participates in a ferrate (II)/ferrate (III) redox system (normal potential of-0.013 V) in the range of the redox potentials of cytochromes. Pyridine-2,6-di(monothiocarboxylic acid) which originally has been considered to be characteristic for Pseudomonas putida has been found recently as a metabolite of other bacterial strains (two of which have been characterized in this paper) as well.

scholarly journals NanoSIMS imaging reveals metabolic stratification within current-producing biofilms

2019 ◽  
Vol 116 (41) ◽  
pp. 20716-20724 ◽  
Author(s):  
Grayson L. Chadwick ◽  
Fernanda Jiménez Otero ◽  
Jeffrey A. Gralnick ◽  
Daniel R. Bond ◽  
Victoria J. Orphan
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Anaerobic Respiration ◽  
Electrical Current ◽  
Total Activity ◽  
Stable Isotope Probing ◽  
Electron Acceptors ◽  
Geobacter Sulfurreducens ◽  
Cellular Growth ◽  
Anode Surface ◽  
Redox Potentials

Metal-reducing bacteria direct electrons to their outer surfaces, where insoluble metal oxides or electrodes act as terminal electron acceptors, generating electrical current from anaerobic respiration. Geobacter sulfurreducens is a commonly enriched electricity-producing organism, forming thick conductive biofilms that magnify total activity by supporting respiration of cells not in direct contact with electrodes. Hypotheses explaining why these biofilms fail to produce higher current densities suggest inhibition by formation of pH, nutrient, or redox potential gradients; but these explanations are often contradictory, and a lack of direct measurements of cellular growth within biofilms prevents discrimination between these models. To address this fundamental question, we measured the anabolic activity of G. sulfurreducens biofilms using stable isotope probing coupled to nanoscale secondary ion mass spectrometry (nanoSIMS). Our results demonstrate that the most active cells are at the anode surface, and that this activity decreases with distance, reaching a minimum 10 µm from the electrode. Cells nearest the electrode continue to grow at their maximum rate in weeks-old biofilms 80-µm-thick, indicating nutrient or buffer diffusion into the biofilm is not rate-limiting. This pattern, where highest activity occurs at the electrode and declines with each cell layer, is present in thin biofilms (<5 µm) and fully grown biofilms (>20 µm), and at different anode redox potentials. These results suggest a growth penalty is associated with respiring insoluble electron acceptors at micron distances, which has important implications for improving microbial electrochemical devices as well as our understanding of syntrophic associations harnessing the phenomenon of microbial conductivity.

scholarly journals How thermophilic Gram-positive organisms perform extracellular electron transfer: characterization of the cell surface terminal reductase OcwA

2019 ◽  
Author(s):  
N.L. Costa ◽  
B. Hermann ◽  
V. Fourmond ◽  
M. Faustino ◽  
M. Teixeira ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Cell Surface ◽  
Electron Acceptors ◽  
Added Value ◽  
Extracellular Electron Transfer ◽  
Bioelectrochemical Systems ◽  
Positive Bacterium ◽  
Gram Positive ◽  
Evolutionary Pathway ◽  
Structural And Functional Properties

AbstractExtracellular electron transfer is the key process underpinning the development of bioelectrochemical systems for the production of energy or added-value compounds. Thermincola potens JR is a promising Gram-positive bacterium to be used in these systems because it is thermophilic. In this paper we describe the structural and functional properties of the nonaheme cytochrome OcwA, which is the terminal reductase of this organism. The structure of OcwA, determined at 2.2Å resolution shows that the overall-fold and organization of the hemes are not related to other metal reductases and instead are similar to that of multiheme cytochromes involved in the biogeochemical cycles of nitrogen and sulfur. We show that, in addition to solid electron acceptors, OcwA can also reduce soluble electron shuttles and oxyanions. These data reveal that OcwA can take the role of a respiratory ‘swiss-army knife’ allowing this organism to grow in environments with rapidly changing availability of terminal electron acceptors without the need for transcriptional regulation and protein synthesis.ImportanceThermophilic Gram-positive organisms were recently shown to be a promising class of organisms to be used in bioelectrochemical systems for the production of electrical energy. These organisms present a thick peptidoglycan layer that was thought to preclude them to perform extracellular electron transfer (i.e. exchange catabolic electrons with solid electron acceptors outside of the cell). In this manuscript we describe the structure and functional mechanisms of the multiheme cytochrome OcwA, the terminal reductase of the Gram-positive bacterium Thermincola potens JR found at the cell surface of this organism. The results presented here show that this protein is unrelated with terminal reductases found at the cell surface of other electroactive organisms. Instead, OcwA is similar to terminal reductases of soluble electron acceptors. Our data reveals that terminal oxidoreductases of soluble and insoluble substrates are evolutionarily related, providing novel insights into the evolutionary pathway of multiheme cytochromes.

scholarly journals 1,4-Naphthoquinone Analogues: Potent Antibacterial Agents and Mode of Action Evaluation

Molecules ◽  
2019 ◽  
Vol 24 (7) ◽  
pp. 1437 ◽  
Author(s):  
Palanisamy Ravichandiran ◽  
Sunirmal Sheet ◽  
Dhanraj Premnath ◽  
Ae Rhan Kim ◽  
Dong Jin Yoo
Keyword(s):  
Antibacterial Activity ◽  
Mode Of Action ◽  
Bacterial Infections ◽  
Antibacterial Agents ◽  
Annexin V ◽  
Ros Generation ◽  
Redox Potentials ◽  
Bacterial Strains ◽  
E Coli ◽  
New Class

1,4-Naphthoquinones have antibacterial activity and are a promising new class of compound that can be used to treat bacterial infections. The goal was to improve effective antibacterial agents; therefore, we synthesized a new class of naphthoquinone hybrids, which contain phenylamino-phenylthio moieties as significant counterparts. Compound 4 was modified as a substituted aryl amide moiety, which enhanced the antibacterial activity of earlier compounds 3 and 4. In this study, five bacterial strains Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes), Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) were used to evaluate the antibacterial potency of synthesized naphthoquinones using the minimal inhibitory concentration (MIC) method. Most of the studied naphthoquinones demonstrated major antibacterial activity with a MIC of 15.6 µg/mL–500 µg/mL. Selected compounds (5a, 5f and 5x) were studied for the mode of action, using intracellular ROS generation, determination of apoptosis by the Annexin V-FITC/PI assay, a bactericidal kinetic study and in silico molecular modelling. Additionally, the redox potentials of the specified compounds were confirmed by cyclic voltammetry (CV).

scholarly journals Flavin-mediated extracellular electron transfer in Gram-positive bacteria Bacillus cereus DIF1 and Rhodococcus ruber DIF2

RSC Advances ◽  
2019 ◽  
Vol 9 (70) ◽  
pp. 40903-40909 ◽  
Author(s):  
Tian Tian ◽  
Xiaoyang Fan ◽  
Man Feng ◽  
Lin Su ◽  
Wen Zhang ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Bacillus Cereus ◽  
Extracellular Electron Transfer ◽  
Rhodococcus Ruber ◽  
Bacterial Strains ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Electrochemically Active

A flavin-mediated EET process was reported here in two new isolated electrochemically active Gram-positive bacterial strains DIF1 and DIF2.

scholarly journals Uranium(VI) Reduction by Anaeromyxobacter dehalogenans Strain 2CP-C

2006 ◽  
Vol 72 (5) ◽  
pp. 3608-3614 ◽  
Author(s):  
Qingzhong Wu ◽  
Robert A. Sanford ◽  
Frank E. L�ffler
Keyword(s):  
Electron Donor ◽  
Ferric Iron ◽  
Model Organism ◽  
Complex Interaction ◽  
Cell Suspensions ◽  
Electron Acceptors ◽  
C Cells ◽  
Inhibitory Effects ◽  
Halogenated Compounds ◽  
Metabolic Versatility

ABSTRACT Previous studies demonstrated growth of Anaeromyxobacter dehalogenans strain 2CP-C with acetate or hydrogen as the electron donor and Fe(III), nitrate, nitrite, fumarate, oxygen, or ortho-substituted halophenols as electron acceptors. In this study, we explored and characterized U(VI) reduction by strain 2CP-C. Cell suspensions of fumarate-grown 2CP-C cells reduced U(VI) to U(IV). More-detailed growth studies demonstrated that hydrogen was the required electron donor for U(VI) reduction and could not be replaced by acetate. The addition of nitrate to U(VI)-reducing cultures resulted in a transitory increase in U(VI) concentration, apparently caused by the reoxidation of reduced U(IV), but U(VI) reduction resumed following the consumption of N-oxyanions. Inhibition of U(VI) reduction occurred in cultures amended with Fe(III) citrate, or citrate. In the presence of amorphous Fe(III) oxide, U(VI) reduction proceeded to completion but the U(VI) reduction rates decreased threefold compared to control cultures. Fumarate and 2-chlorophenol had no inhibitory effects on U(VI) reduction, and both electron acceptors were consumed concomitantly with U(VI). Since cocontaminants (e.g., nitrate, halogenated compounds) and bioavailable ferric iron are often encountered at uranium-impacted sites, the metabolic versatility makes Anaeromyxobacter dehalogenans a promising model organism for studying the complex interaction of multiple electron acceptors in U(VI) reduction and immobilization.

scholarly journals In Situ Bioremediation Techniques to Reduce Total Organic Matter Oversaturation of Fluvial Sediments: An Experimental Study

2020 ◽  
Vol 10 (12) ◽  
pp. 4308
Author(s):  
Carlos Rochera ◽  
Antonio Picazo ◽  
Nayeli Murueta ◽  
Antonio Camacho
Keyword(s):  
Organic Matter ◽  
Anaerobic Respiration ◽  
Electron Acceptors ◽  
Biologically Active ◽  
Inorganic Nutrients ◽  
Limiting Factors ◽  
Bacterial Strains ◽  
In Situ Experiment ◽  
Significant Drop

An in situ experiment was performed in sediments of River Magro (east Spain) in order to evaluate the usefulness of microbial bioremediation, both bioaugmentation and biostimulation, as a tool for reducing the excessive organic matter (OM) content in dammed river stretches due to historical wastewater spilling. The study had a prospective approach focused on the application of a biologically active commercial product (BAP), consisting of a mix of bacterial strains, ectoenzymes, and nutrients, where a range of concentrations and temporal dosages of the product were experimentally assayed in situ. They were further combined with the addition of potential organic enhancers, such as acetate, as well as of inhibitors of specific microbial guilds. On the other hand, inorganic electron acceptors for the anaerobic respiration of the organic matter were additionally amended. In additional assays, the BAP additions were combined with inorganic nutrients amendments, or even the latter were tested alone. These combinative treatments aimed at exploring the possible enhancement of synergistic or antagonistic interactions among the amended compounds, as well as the eventual effect of growth limiting factors. The single BAP additions of 50 g/m3 led to OM reductions of up to 17%, and significant removals of nitrogen or phosphorus were additionally observed by increasing or by fractioning the BAP dosage, respectively. However, a better response using the same amount of the BAP was obtained by supplementing it with sodium acetate. In this case, reductions of the OM content reached up to 35% of the accumulated OM, thus indicating that a complementary stimulus is still necessary to run out barriers towards the final steps of the anaerobic OM digestion. This treatment was also linked to the strongest significant drop in the TP content of the sediments. Neither the addition of inorganic electron acceptors nor inorganic nutrients improved the results, or they were even antagonistic of the degradative potential of the BAP product. Apparently, the occurrence of acetoclastic microorganisms, which was demonstrated by high throughput DNA-sequencing, was critical for the optimal OM reductions in the sediments. This exploratory study demonstrates that the applicability of BAPs can be extended to cover the remediation of fluvial ecosystems, and support the complementarity of different bioremediation strategies.

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