Oxidation of glycerol, lactate, and propionate by Propionibacterium freudenreichii in a poised-potential amperometric culture system

Emde, Rainer; Schink, Bernhard

doi:10.1007/bf00248435

Cited by 50 publications

(41 citation statements)

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“…Pyocyanin can subsequently be reoxidized through abiotic electron transfer to oxygen. Differences in central metabolism depending on the presence or absence of synthetic and environmental electron shuttles have been reported for fermentative bacteria (5,19,20) and apparently arise from the effects of extracellular electron shuttling on the intracellular redox state. If the mechanism of redox balancing depicted in Fig.…”

Section: Discussionmentioning

confidence: 97%

“…For fermentative organisms such as E. coli and Propionibacterium freudenreichii, the addition of the synthetic redox-cycling compound ferricyanide has been shown to alter carbon flux through central metabolic pathways. Particularly when the reoxidation of this compound is coupled to electron transfer to an electrode, ferricyanide shifted the fermentation balance away from ethanol and propionate, products that require NADH for their formation, toward acetate, a more oxidized product (19,20). This implies that the ferricyanide acts as an electron shuttle from major pools of reductant inside the cell, such as NADH, to the electrode, thereby lessening the need for formation of more reduced fermentation products to dissipate cellular reductant.…”

Section: Figmentioning

confidence: 99%

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Pyocyanin Alters Redox Homeostasis and Carbon Flux through Central Metabolic Pathways in Pseudomonas aeruginosa PA14

Price-Whelan¹,

2007

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The opportunistic pathogen Pseudomonas aeruginosa produces colorful, redox-active antibiotics called phenazines. Excretion of pyocyanin, the best-studied natural phenazine, is responsible for the bluish tint of sputum and pus associated with P. aeruginosa infections in humans. Although the toxicity of pyocyanin for other bacteria, as well as its role in eukaryotic infection, has been studied extensively, the physiological relevance of pyocyanin metabolism for the producing organism is not well understood. Pyocyanin reduction by P. aeruginosa PA14 is readily observed in standing liquid cultures that have consumed all of the oxygen in the medium. We investigated the physiological consequences of pyocyanin reduction by assaying intracellular concentrations of NADH and NAD ؉ in the wild-type strain and a mutant defective in phenazine production. We found that the mutant accumulated more NADH in stationary phase than the wild type. This increased accumulation correlated with a decrease in oxygen availability and was relieved by the addition of nitrate. Pyocyanin addition to a phenazine-null mutant also decreased intracellular NADH levels, suggesting that pyocyanin reduction facilitates redox balancing in the absence of other electron acceptors. Analysis of extracellular organic acids revealed that pyocyanin stimulated stationary-phase pyruvate excretion in P. aeruginosa PA14, indicating that pyocyanin may also influence the intracellular redox state by decreasing carbon flux through central metabolic pathways.

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Section: Discussionmentioning

confidence: 97%

Section: Figmentioning

confidence: 99%

Pyocyanin Alters Redox Homeostasis and Carbon Flux through Central Metabolic Pathways in Pseudomonas aeruginosa PA14

Price-Whelan¹,

2007

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“…Several fermenting bacteria, e.g., Propionibacterium sp. can reduce such external electron carriers (Benz et al 1998;Emde & Schink 1990) and can deliver electrons this way indirectly to Fe(III) minerals as well although they have never been regarded as iron-reducing bacteria. Electrons from quinoid carriers can as well be taken up by, e.g., nitrate-reducing bacteria or others (Lovley et al 1999), and humic compounds can thus mediate electron transfer systems between rather different types of bacteria that would usually not be thought of as cooperation partners.…”

Section: Types Of Metabolite Transfermentioning

confidence: 99%

Untitled

Schink

2002

Antonie Van Leeuwenhoek

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259

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After several decades of microbiological research has focused on pure cultures, synergistic effects between different types of microorganisms find increasing interest. Interspecies interactions between prokaryotic cells have been studied into depth mainly with respect to syntrophic cooperations involved in methanogenic degradation of electron-rich substrates such as fatty acids, alcohols, and aromatics. Partners involved in these processes have to run their metabolism at minimal energy increments, with only fractions of an ATP unit synthesized per substrate molecule metabolized, and their cooperation is intensified by close proximity of the partner cells. New examples of such syntrophic activities are anaerobic methane oxidation by presumably methanogenic and sulfate-reducing prokaryotes, and microbially mediated pyrite formation. Syntrophic relationships have also been discovered to be involved in the anaerobic metabolization of amino acids and sugars where energetical restrictions do not necessarily force the partner organisms into strict interdependencies. The most highly developed cooperative systems among prokaryotic cells appear to be the structurally organized phototrophic consortia of the Chlorochromatium and Pelochromatium type in which phototrophic and chemotrophic bacteria not only exchange metabolites but also interact at the level of growth coordination and tactic behaviour.

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“…A major shortcoming is that most microorganisms studied to date only partially oxidize their organic substrates and transfer a portion of these electrons to electrodes (8,9,11,12,24,25). Furthermore, electrical current was generated only when soluble mediator compounds were added to these microbial cultures to facilitate electron transfer from the bacteria to the electrodes.…”

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confidence: 99%

“…The electron transfer from G. sulfurreducens to electrodes is different from previously described microbial fuel cells. For instance, in microbial fuel cells where the metabolism of sugars or organic acids was shifted to end products more oxidized than the products formed during fermentation in the absence of an electrode, a significant fraction of the electrons available in the initial electron donor remained in the end products (8,9,12,24). Of the electrons released from this partial metabolism, typically only 30 to 60% were recovered by electrodes (6,12,13).…”

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confidence: 99%

Electricity Production byGeobacter sulfurreducensAttached to Electrodes

Bond

Lovley

2003

Appl Environ Microbiol

2,000

1,240

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Previous studies have suggested that members of the Geobacteraceae can use electrodes as electron acceptors for anaerobic respiration. In order to better understand this electron transfer process for energy production, Geobacter sulfurreducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate or hydrogen was the electron donor. The electron-accepting electrodes were maintained at oxidizing potentials by connecting them to similar electrodes in oxygenated medium (fuel cells) or to potentiostats that poised electrodes at ؉0.2 V versus an Ag/AgCl reference electrode (poised potential). When a small inoculum of G. sulfurreducens was introduced into electrode-containing chambers, electrical current production was dependent upon oxidation of acetate to carbon dioxide and increased exponentially, indicating for the first time that electrode reduction supported the growth of this organism. When the medium was replaced with an anaerobic buffer lacking nutrients required for growth, acetate-dependent electrical current production was unaffected and cells attached to these electrodes continued to generate electrical current for weeks. This represents the first report of microbial electricity production solely by cells attached to an electrode. Electrode-attached cells completely oxidized acetate to levels below detection (<10 M), and hydrogen was metabolized to a threshold of 3 Pa. The rates of electron transfer to electrodes (0.21 to 1.2 mol of electrons/mg of protein/min) were similar to those observed for respiration with Fe(III) citrate as the electron acceptor (E o ‫73.0؉؍‬ V). The production of current in microbial fuel cell (65 mA/m 2 of electrode surface) or poised-potential (163 to 1,143 mA/m 2 ) mode was greater than what has been reported for other microbial systems, even those that employed higher cell densities and electron-shuttling compounds. Since acetate was completely oxidized, the efficiency of conversion of organic electron donor to electricity was significantly higher than in previously described microbial fuel cells. These results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G. sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode.

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Oxidation of glycerol, lactate, and propionate by Propionibacterium freudenreichii in a poised-potential amperometric culture system

Cited by 50 publications

References 20 publications

Pyocyanin Alters Redox Homeostasis and Carbon Flux through Central Metabolic Pathways in Pseudomonas aeruginosa PA14

Pyocyanin Alters Redox Homeostasis and Carbon Flux through Central Metabolic Pathways in Pseudomonas aeruginosa PA14

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Electricity Production byGeobacter sulfurreducensAttached to Electrodes

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