scholarly journals Interactions between the Fe(III)-Reducing Bacterium Geobacter sulfurreducens and Arsenate, and Capture of the Metalloid by Biogenic Fe(II)

2005 ◽  
Vol 71 (12) ◽  
pp. 8642-8648 ◽  
Author(s):  
F. S. Islam ◽  
R. L. Pederick ◽  
A. G. Gault ◽  
L. K. Adams ◽  
D. A. Polya ◽  
...  
Keyword(s):  
Microbial Communities ◽  
Electron Acceptor ◽  
West Bengal ◽  
Arsenic Species ◽  
Geobacter Sulfurreducens ◽  
Terminal Electron Acceptor ◽  
Genetic Potential ◽  
Enzymatic Reduction ◽  
Culture Supernatants ◽  
Ferrous Carbonate

ABSTRACT Previous work has shown that microbial communities in As-mobilizing sediments from West Bengal were dominated by Geobacter species. Thus, the potential of Geobacter sulfurreducens to mobilize arsenic via direct enzymatic reduction and indirect mechanisms linked to Fe(III) reduction was analyzed. G. sulfurreducens was unable to conserve energy for growth via the dissimilatory reduction of As(V), although it was able to grow in medium containing fumarate as the terminal electron acceptor in the presence of 500 μM As(V). There was also no evidence of As(III) in culture supernatants, suggesting that resistance to 500 μM As(V) was not mediated by a classical arsenic resistance operon, which would rely on the intracellular reduction of As(V) and the efflux of As(III). When the cells were grown using soluble Fe(III) as an electron acceptor in the presence of As(V), the Fe(II)-bearing mineral vivianite was formed. This was accompanied by the removal of As, predominantly as As(V), from solution. Biogenic siderite (ferrous carbonate) was also able to remove As from solution. When the organism was grown using insoluble ferrihydrite as an electron acceptor, Fe(III) reduction resulted in the formation of magnetite, again accompanied by the nearly quantitative sorption of As(V). These results demonstrate that G. sulfurreducens, a model Fe(III)-reducing bacterium, did not reduce As(V) enzymatically, despite the apparent genetic potential to mediate this transformation. However, the reduction of Fe(III) led to the formation of Fe(II)-bearing phases that are able to capture arsenic species and could act as sinks for arsenic in sediments.

scholarly journals Geobacter sulfurreducens Can Grow with Oxygen as a Terminal Electron Acceptor

2004 ◽  
Vol 70 (4) ◽  
pp. 2525-2528 ◽  
Author(s):  
W. C. Lin ◽  
M. V. Coppi ◽  
D. R. Lovley
Keyword(s):  
Electron Acceptor ◽  
Atmospheric Oxygen ◽  
Geobacter Sulfurreducens ◽  
Terminal Electron Acceptor ◽  
Anoxic Conditions ◽  
Strict Anaerobe ◽  
Subsurface Environments

ABSTRACT Geobacter sulfurreducens, previously classified as a strict anaerobe, tolerated exposure to atmospheric oxygen for at least 24 h and grew with oxygen as the sole electron acceptor at concentrations of 10% or less in the headspace. These results help explain how Geobacter species may survive in oxic subsurface environments, being poised to rapidly take advantage of the development of anoxic conditions.

scholarly journals Genetic Characterization of a Single Bifunctional Enzyme for Fumarate Reduction and Succinate Oxidation in Geobacter sulfurreducens and Engineering of Fumarate Reduction in Geobacter metallireducens

2006 ◽  
Vol 188 (2) ◽  
pp. 450-455 ◽  
Author(s):  
Jessica E. Butler ◽  
Richard H. Glaven ◽  
Abraham Esteve-Núñez ◽  
Cinthia Núñez ◽  
Evgenya S. Shelobolina ◽  
...  
Keyword(s):  
Succinate Dehydrogenase ◽  
Dehydrogenase Activity ◽  
Mutant Strain ◽  
Electron Acceptor ◽  
Geobacter Sulfurreducens ◽  
Fumarate Reductase ◽  
Succinate Dehydrogenase Activity ◽  
Geobacter Metallireducens ◽  
Terminal Electron Acceptor ◽  
Fumarate Reduction

ABSTRACT The mechanism of fumarate reduction in Geobacter sulfurreducens was investigated. The genome contained genes encoding a heterotrimeric fumarate reductase, FrdCAB, with homology to the fumarate reductase of Wolinella succinogenes and the succinate dehydrogenase of Bacillus subtilis. Mutation of the putative catalytic subunit of the enzyme resulted in a strain that lacked fumarate reductase activity and was unable to grow with fumarate as the terminal electron acceptor. The mutant strain also lacked succinate dehydrogenase activity and did not grow with acetate as the electron donor and Fe(III) as the electron acceptor. The mutant strain could grow with acetate as the electron donor and Fe(III) as the electron acceptor if fumarate was provided to alleviate the need for succinate dehydrogenase activity in the tricarboxylic acid cycle. The growth rate of the mutant strain under these conditions was faster and the cell yields were higher than for wild type grown under conditions requiring succinate dehydrogenase activity, suggesting that the succinate dehydrogenase reaction consumes energy. An orthologous frdCAB operon was present in Geobacter metallireducens, which cannot grow with fumarate as the terminal electron acceptor. When a putative dicarboxylic acid transporter from G. sulfurreducens was expressed in G. metallireducens, growth with fumarate as the sole electron acceptor was possible. These results demonstrate that, unlike previously described organisms, G. sulfurreducens and possibly G. metallireducens use the same enzyme for both fumarate reduction and succinate oxidation in vivo.

scholarly journals Oxygen as a Virulence Determinant in Polymicrobial Infections

mBio ◽  
2016 ◽  
Vol 7 (4) ◽  
Author(s):  
Elizabeth M. Selleck ◽  
Michael S. Gilmore
Keyword(s):  
Microbial Communities ◽  
Electron Acceptor ◽  
Whole Genome ◽  
Streptococcus Gordonii ◽  
Terminal Electron Acceptor ◽  
Virulence Determinant ◽  
Oral Microbes ◽  
Polymicrobial Infections ◽  
Thigh Abscess

ABSTRACT Infections caused by multiple organisms, or polymicrobial infections, are likely more common than is broadly appreciated. Interaction among microbial communities (and with their host) can change the infection landscape by subverting immunity, providing nutrients and inhibiting competing microbes. Stacy et al. (A. Stacy, D. Fleming, R. J. Lamont, K. P. Rumbaugh, and M. Whiteley, mBio 7:e00782-16, 2016, http://dx.doi.org/10.1128/mBio.00782-16 ) described a novel mechanism that results in synergistic growth of oral microbes Aggregatibacter actinomycetemcomitans and Streptococcus gordonii . The authors used whole-genome fitness profiling by transposon sequencing (Tn-seq) to identify genes differentially required for growth in vitro versus in a mono- or coinfection in a thigh abscess model. They found that coinfection with S. gordonii allowed A. actinomycetemcomitans to shift from an anaerobic to an aerobic mode of growth. This shift involved the production of a terminal electron acceptor H 2 O 2 by S. gordonii and increased A. actinomycetemcomitans persistence—an interaction termed “cross-respiration.”

Effects of terminal electron acceptor strength on film morphology and ternary memory performance of triphenylamine donor based devices

2013 ◽  
Vol 1 (24) ◽  
pp. 3816 ◽  
Author(s):  
Hao Zhuang ◽  
Qijian Zhang ◽  
Yongxiang Zhu ◽  
Xufeng Xu ◽  
Haifeng Liu ◽  
...  
Keyword(s):  
Electron Acceptor ◽  
Memory Performance ◽  
Film Morphology ◽  
Terminal Electron Acceptor

Magnetovibrio blakemorei gen. nov., sp. nov., a magnetotactic bacterium ( Alphaproteobacteria : Rhodospirillaceae ) isolated from a salt marsh

2013 ◽  
Vol 63 (Pt_5) ◽  
pp. 1824-1833 ◽  
Author(s):  
Dennis A. Bazylinski ◽  
Timothy J. Williams ◽  
Christopher T. Lefèvre ◽  
Denis Trubitsyn ◽  
Jiasong Fang ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Electron Acceptor ◽  
Anaerobic Growth ◽  
Rrna Gene ◽  
Magnetotactic Bacterium ◽  
Single Chain ◽  
Circular Chromosome ◽  
Terminal Electron Acceptor ◽  
Content Type ◽  
Link Type

A magnetotactic bacterium, designated strain MV-1T, was isolated from sulfide-rich sediments in a salt marsh near Boston, MA, USA. Cells of strain MV-1T were Gram-negative, and vibrioid to helicoid in morphology. Cells were motile by means of a single polar flagellum. The cells appeared to display a transitional state between axial and polar magnetotaxis: cells swam in both directions, but generally had longer excursions in one direction than the other. Cells possessed a single chain of magnetosomes containing truncated hexaoctahedral crystals of magnetite, positioned along the long axis of the cell. Strain MV-1T was a microaerophile that was also capable of anaerobic growth on some nitrogen oxides. Salinities greater than 10 % seawater were required for growth. Strain MV-1T exhibited chemolithoautotrophic growth on thiosulfate and sulfide with oxygen as the terminal electron acceptor (microaerobic growth) and on thiosulfate using nitrous oxide (N2O) as the terminal electron acceptor (anaerobic growth). Chemo-organoautotrophic and methylotrophic growth was supported by formate under microaerobic conditions. Autotrophic growth occurred via the Calvin–Benson–Bassham cycle. Chemo-organoheterotrophic growth was supported by various organic acids and amino acids, under microaerobic and anaerobic conditions. Optimal growth occurred at pH 7.0 and 26–28 °C. The genome of strain MV-1T consisted of a single, circular chromosome, about 3.7 Mb in size, with a G+C content of 52.9–53.5 mol%.Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain MV-1T belongs to the family Rhodospirillaceae within the Alphaproteobacteria , but is not closely related to the genus Magnetospirillum . The name Magnetovibrio blakemorei gen. nov., sp. nov. is proposed for strain MV-1T. The type strain of Magnetovibrio blakemorei is MV-1T ( = ATCC BAA-1436T  = DSM 18854T).

Urinary arsenic species in an arsenic-affected area of West Bengal, India (part III)

2005 ◽  
Vol 19 (2) ◽  
pp. 246-253 ◽  
Author(s):  
Hiroshi Tokunaga ◽  
Tarit Roychowdhury ◽  
Tadashi Uchino ◽  
Masanori Ando
Keyword(s):  
West Bengal ◽  
Arsenic Species ◽  
Affected Area ◽  
Urinary Arsenic ◽  
Urinary Arsenic Species

scholarly journals Identification of different putative outer membrane electron conduits necessary for Fe(III) citrate, Fe(III) oxide, Mn(IV) oxide, or electrode reduction by Geobacter sulfurreducens

2017 ◽  
Author(s):  
Fernanda Jiménez Otero ◽  
Chi Ho Chan ◽  
Daniel R. Bond
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Electron Acceptor ◽  
Single Gene ◽  
Gene Clusters ◽  
Geobacter Sulfurreducens ◽  
Transcriptional Analysis ◽  
Growth Defect ◽  
Redox Potentials ◽  
Wild Type

AbstractAt least five gene clusters in the Geobacter sulfurreducens genome encode putative ‘electron conduits’ implicated in electron transfer across the outer membrane, each containing a periplasmic multiheme c-type cytochrome, integral outer membrane anchor, and outer membrane redox lipoprotein(s). Markerless single gene cluster deletions and all possible multiple deletion combinations were constructed and grown with soluble Fe(III) citrate, Fe(III)- and Mn(IV)-oxides, and graphite electrodes poised at +0.24 V and −0.1 V vs. SHE. Different gene clusters were necessary for reduction of each electron acceptor. During metal oxide reduction, deletion of the previously described omcBC cluster caused defects, but deletion of additional components in an ΔomcBC background, such as extEFG, were needed to produce defects greater than 50% compared to wild type. Deletion of all five gene clusters abolished all metal reduction. During electrode reduction, only the ΔextABCD mutant had a severe growth defect at both redox potentials, while this mutation did not affect Fe(III)-oxide, Mn(IV)-oxide, or Fe(III) citrate reduction. Some mutants containing only one cluster were able to reduce particular terminal electron acceptors better than wild type, suggesting routes for improvement by targeting specific electron transfer pathways. Transcriptomic comparisons between fumarate and electrode-based growth showed all of these ext clusters to be constitutive, and transcriptional analysis of the triple-deletion strain containing only extABCD detected no significant changes in expression of known redox proteins or pili components. These genetic experiments reveal new outer membrane conduit complexes necessary for growth of G. sulfurreducens, depending on the available extracellular electron acceptor.

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