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Chemiluminescence as a PDT light source for microbial control

FERRAZ, Ruy C. M. C.; FONTANA, Carla R.; RIBEIRO, Ana P. de; TRINDADE, Flavia Z.; BARTOLONI, Fernando H.; BAADER, Josef W.; LINS, Emery C.; BAGNATO, Vanderlei S.; KURACHI, Cristina
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
468.1141%
The photodynamic therapy (PDT) is a combination of using a photosensitizer agent, light and oxygen that can cause oxidative cellular damage. This technique is applied in several cases, including for microbial control. The most extensively studied light sources for this purpose are lasers and LED-based systems. Few studies treat alternative light sources based PDT. Sources which present flexibility, portability and economic advantages are of great interest. In this study, we evaluated the in vitro feasibility for the use of chemiluminescence as a PDT light source to induce Staphylococcus aureus reduction. The Photogem (R) concentration varied from 0 to 75 mu g/ml and the illumination time varied from 60 min to 240 min. The long exposure time was necessary due to the low irradiance achieved with chemiluminescence reaction at mu W/cm(2) level. The results demonstrated an effective microbial reduction of around 98% for the highest photosensitizer concentration and light dose. These data suggest the potential use of chemiluminescence as a light source for PDT microbial control, with advantages in terms of flexibility, when compared with conventional sources. (C) 2011 Elsevier B.V. All rights reserved.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq

Avaliação da viabilidade da quimiluminescência como fonte de luz em terapia fotodinâmica para controle microbiano.; Evaluation of the viability of the chemiluminescence as a PDT light source for microbial control

Ferraz, Ruy Carvalho Mattosinho de Castro
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/02/2010 PT
Relevância na Pesquisa
473.07938%
A terapia fotodinâmica é a combinação do agente fotossensibilizador, da fonte de luz e do oxigênio que pode resultar na oxidação de biomoléculas e gerar danos celulares. Esta técnica é aplicada em diversas situações, desde o controle microbiológico até o tratamento de câncer. A maioria dos estudos utiliza as fontes de luz tradicionais, ou seja, lasers, sistemas à LED e lâmpadas. No entanto, poucos são os estudos que se concentram em propostas de fonte de luz alternativas. Iluminação portátil, flexível e independente de energia elétrica são características de grande interesse, principalmente, aos países em desenvolvimento no qual há uma grande parcela da população não assistida por hospitais de referência, além de cidades que não possuem o fornecimento de energia elétrica. Neste estudo, foi avaliada a viabilidade do uso, in vitro, da quimiluminescência como uma fonte de luz para a terapia fotodinâmica, induzindo a redução microbiana de Staphylococcus aureus. A quimiluminescência é uma reação química onde por meio da mistura de reagentes líquidos ocorre a emissão de luz sem a necessidade de qualquer ativação externa. Previamente aos estudos da aplicação terapia fotodinâmica in vitro, foram avaliadas diversas reações de quimiluminescência no intuito de estabelecer as características mais viáveis ao efeito fotodinâmico. Através de um modelo similar a teoria de Förster...

Avaliação in vivo da redução microbiana após preparo do canal radicular com auxílio do sistema EndoVac; In vivo evaluation of microbial reduction after root canal preparation with the aid of the EndoVac system

Bitencourt, Leandro Manenti
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/09/2012 PT
Relevância na Pesquisa
454.80625%
O presente estudo teve por objetivo avaliar in vivo a eficácia do preparo de canais radiculares na redução bacteriana em dentes portadores de periodontite apical primária, com auxílio do sistema EndoVac de irrigação e aspiração. Foram coletadas amostras dos canais radiculares de 20 pacientes, antes (S1) e após (S2) o preparo com instrumentos rotatórios Protaper, variando somente a técnica utilizada para irrigação e aspiração: Grupo A (irrigação convencional n=10) e Grupo B (irrigação com auxílio do sistema EndoVac n=10). Após a extração do DNA presente nas amostras, este foi quantificado através da reação de PCR em tempo real, pelo método SYBR Green, identificando o número de cópias do gene 16SrRNA. Em todas as amostras, com exceção de uma pós-preparo com EndoVac, foram identificadas cópias do gene alvo. A média para todos os casos foi de 1,6 X 108 e 8,8 X 105 cópias do 16SrRNA, antes e após o preparo, respectivamente. Para os grupos isoladamente, os mesmos valores foram: 2,0 X 108 e 5,5 X 105 (convencional), e 1,1 X 108 e 1,2 X 106 (EndoVac). O percentual médio de redução foi de 97,52% (97,02% para convencional e 98,04% para o EndoVac). O teste de Mann-Whitney permitiu concluir que ambas as técnicas reduziram significativamente os microrganismos presentes antes do preparo (p<0...

Chemiluminescence as a PDT light source for microbial control

Ferraz, Ruy C. M. C.; Fontana, Carla R.; de Ribeiro, Ana P.; Trindade, Flavia Z.; Bartoloni, Fernando H.; Baader, Josef W.; Lins, Emery C.; Bagnato, Vanderlei S.; Kurachi, Cristina
Fonte: Elsevier B.V. Sa Publicador: Elsevier B.V. Sa
Tipo: Artigo de Revista Científica Formato: 87-92
ENG
Relevância na Pesquisa
468.1141%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); The photodynamic therapy (PDT) is a combination of using a photosensitizer agent, light and oxygen that can cause oxidative cellular damage. This technique is applied in several cases, including for microbial control. The most extensively studied light sources for this purpose are lasers and LED-based systems. Few studies treat alternative light sources based PDT. Sources which present flexibility, portability and economic advantages are of great interest. In this study, we evaluated the in vitro feasibility for the use of chemiluminescence as a PDT light source to induce Staphylococcus aureus reduction. The Photogem (R) concentration varied from 0 to 75 mu g/ml and the illumination time varied from 60 min to 240 min. The long exposure time was necessary due to the low irradiance achieved with chemiluminescence reaction at mu W/cm(2) level. The results demonstrated an effective microbial reduction of around 98% for the highest photosensitizer concentration and light dose. These data suggest the potential use of chemiluminescence as a light source for PDT microbial control, with advantages in terms of flexibility...

Microbial redox processes in deep subsurface environments and the potential application of (per)chlorate in oil reservoirs

Liebensteiner, Martin G.; Tsesmetzis, N.; Stams, A. J. M.; Lomans, Bart P.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
471.3432%
The ability of microorganisms to thrive under oxygen-free conditions in subsurface environments relies on the enzymatic reduction of oxidized elements, such as sulfate, ferric iron, or CO2, coupled to the oxidation of inorganic or organic compounds. A broad phylogenetic and functional diversity of microorganisms from subsurface environments has been described using isolation-based and advanced molecular ecological techniques. The physiological groups reviewed here comprise iron-, manganese-, and nitrate-reducing microorganisms. In the context of recent findings also the potential of chlorate and perchlorate [jointly termed (per)chlorate] reduction in oil reservoirs will be discussed. Special attention is given to elevated temperatures that are predominant in the deep subsurface. Microbial reduction of (per)chlorate is a thermodynamically favorable redox process, also at high temperature. However, knowledge about (per)chlorate reduction at elevated temperatures is still scarce and restricted to members of the Firmicutes and the archaeon Archaeoglobus fulgidus. By analyzing the diversity and phylogenetic distribution of functional genes in (meta)genome databases and combining this knowledge with extrapolations to earlier-made physiological observations we speculate on the potential of (per)chlorate reduction in the subsurface and more precisely oil fields. In addition...

Influence of aqueous ozone, blanching and combined treatments on microbial load of red bell peppers, strawberries and watercress

Alexandre, Elisabete M. C.; Santos-Pedro, Dora M.; Brandão, Teresa R. S.; Silva, Cristina L. M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2011 ENG
Relevância na Pesquisa
469.5644%
The effectiveness of ozone in aqueous solution treatment on microbial inactivation was studied for three combinations microorganism/food: Listeria innocua/red bell peppers (artificially inoculated), total mesophiles/strawberries, and total coliforms/watercress, with two concentrations (0.3 and 2.0 ppm). Blanching treatments (50–60 C) were also individually applied and in combination with ozone, for studying possible synergistic effects. In relation to ozone treatments, the highest microbial reductions were obtained for the highest concentration with the highest treatment time (3 min). Under those conditions, L. innocua/peppers, total mesophiles/strawberries and total coliforms/watercress were reduced respectively 2.8 ± 0.5, 2.3 ± 0.4 and 1.7 ± 0.4 log-cycles. However, a substantial portion of the microbial populations were reduced by water washing alone, and the presence of ozone generally added an additional reduction of 0.5–1.0 log-cycles. If ozone at the highest concentration is used, the treatment impacts on L. innocua/peppers and total mesophiles/strawberries load reductions were equivalent to a blanching at 50 C (for the same treatment times). Combining blanching and ozone did not generate synergistic effects, and in some situations microbial reductions were lower than the ones observed when treatments were applied independently.

Reduction of chromium (VI) by the indirect action of Thiobacillus thioparus

Donati,E.; Oliver,C.; Curutchet,G.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2003 EN
Relevância na Pesquisa
456.27156%
The microbial reduction of chromium(VI) to chromium(III) has been one of the most widely studied forms of metal bioremediation. Recently, we have found that Thiobacillus ferrooxidans and Thiobacillus thiooxidans, growing on elemental sulphur, can indirectly promote chromium(VI) reduction by producing reducing agents such as sulphite and thiosulphate, which abiotically reduce chromium(VI). Those species of Thiobacillus are acidophilic bacteria which grow optimally at pH values lower than 4. However, most of those reducing agents are stabilised at higher pH values. Thus, the present paper reports on the ability to reduce chromium(VI) using another specie of Thiobacilli, Thiobacillus thioparus, which is able to grow at pH close to 7.0. T. thioparus cultures were carried out in a fermentation vessel containing medium and sulphur as the sole energy source and maintained at 30ºC and 400 rpm. The pH was adjusted to 6.0, 7.0 or 8.0 and maintained with the automatic addition of KOH. Our results show high chromium (VI) reduction values (close to 100% at the end of bacterial growth) at the three pH values. The results of these experiments are very promising for development of a microbiological process to be used in the detoxification of chromium(VI)-polluted effluents.

Microbial Reduction of Fe(III) in Acidic Sediments: Isolation of Acidiphilium cryptum JF-5 Capable of Coupling the Reduction of Fe(III) to the Oxidation of Glucose

Küsel, Kirsten; Dorsch, Tanja; Acker, Georg; Stackebrandt, Erko
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /08/1999 EN
Relevância na Pesquisa
472.14336%
To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12°C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H2 was consumed by acidic sediments and yielded additional amounts of Fe(II) in a ratio of approximately 1:2. In contrast, supplemental lactate did not stimulate the formation of Fe(II). Supplemental acetate was not consumed and inhibited the formation of Fe(II). Most-probable-number estimates demonstrated that glucose-utilizing acidophilic Fe(III)-reducing bacteria approximated to 1% of the total direct counts of 4′,6-diamidino-2-phenylindole-stained bacteria. From the highest growth-positive dilution of the most-probable-number series at pH 2.3 supplemented with glucose, an isolate, JF-5, that could dissimilate Fe(III) was obtained. JF-5 was an acidophilic, gram-negative, facultative anaerobe that completely oxidized the following substrates via the dissimilation of Fe(III): glucose...

Microbial Activity in Aquatic Environments Measured by Dimethyl Sulfoxide Reduction and Intercomparison with Commonly Used Methods

Griebler, Christian; Slezak, Doris
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /01/2001 EN
Relevância na Pesquisa
382.09703%
A new method to determine microbial (bacterial and fungal) activity in various freshwater habitats is described. Based on microbial reduction of dimethyl sulfoxide (DMSO) to dimethyl sulfide (DMS), our DMSO reduction method allows measurement of the respiratory activity in interstitial water, as well as in the water column. DMSO is added to water samples at a concentration (0.75% [vol/vol] or 106 mM) high enough to compete with other naturally occurring electron acceptors, as determined with oxygen and nitrate, without stimulating or inhibiting microbial activity. Addition of NaN3, KCN, and formaldehyde, as well as autoclaving, inhibited the production of DMS, which proves that the reduction of DMSO is a biotic process. DMSO reduction is readily detectable via the formation of DMS even at low microbial activities. All water samples showed significant DMSO reduction over several hours. Microbially reduced DMSO is recovered in the form of DMS from water samples by a purge and trap system and is quantified by gas chromatography and detection with a flame photometric detector. The DMSO reduction method was compared with other methods commonly used for assessment of microbial activity. DMSO reduction activity correlated well with bacterial production in predator-free batch cultures. Cell-production-specific DMSO reduction rates did not differ significantly in batch cultures with different nutrient regimes but were different in different growth phases. Overall...

Chemical and Biological Interactions during Nitrate and Goethite Reduction by Shewanella putrefaciens 200

Cooper, D. Craig; Picardal, Flynn W.; Schimmelmann, Arndt; Coby, Aaron J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2003 EN
Relevância na Pesquisa
376.2374%
Although previous research has demonstrated that NO3− inhibits microbial Fe(III) reduction in laboratory cultures and natural sediments, the mechanisms of this inhibition have not been fully studied in an environmentally relevant medium that utilizes solid-phase, iron oxide minerals as a Fe(III) source. To study the dynamics of Fe and NO3− biogeochemistry when ferric (hydr)oxides are used as the Fe(III) source, Shewanella putrefaciens 200 was incubated under anoxic conditions in a low-ionic-strength, artificial groundwater medium with various amounts of NO3− and synthetic, high-surface-area goethite. Results showed that the presence of NO3− inhibited microbial goethite reduction more severely than it inhibited microbial reduction of the aqueous or microcrystalline sources of Fe(III) used in other studies. More interestingly, the presence of goethite also resulted in a twofold decrease in the rate of NO3− reduction, a 10-fold decrease in the rate of NO2− reduction, and a 20-fold increase in the amounts of N2O produced. Nitrogen stable isotope experiments that utilized δ15N values of N2O to distinguish between chemical and biological reduction of NO2− revealed that the N2O produced during NO2− or NO3− reduction in the presence of goethite was primarily of abiotic origin. These results indicate that concomitant microbial Fe(III) and NO3− reduction produces NO2− and Fe(II)...

Rapid Assay for Microbially Reducible Ferric Iron in Aquatic Sediments

Lovley, Derek R.; Phillips, Elizabeth J. P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1987 EN
Relevância na Pesquisa
376.3157%
The availability of ferric iron for microbial reduction as directly determined by the activity of iron-reducing organisms was compared with its availability as determined by a newly developed chemical assay for microbially reducible iron. The chemical assay was based on the reduction of poorly crystalline ferric iron by hydroxylamine under acidic conditions. There was a strong correlation between the extent to which hydroxylamine could reduce various synthetic ferric iron forms and the susceptibility of the iron to microbial reduction in an enrichment culture of iron-reducing organisms. When sediments that contained hydroxylamine-reducible ferric iron were incubated under anaerobic conditions, ferrous iron accumulated as the concentration of hydroxylamine-reducible ferric iron declined over time. Ferrous iron production stopped as soon as the hydroxylamine-reducible ferric iron was depleted. In anaerobic incubations of reduced sediments that did not contain hydroxylamine-reducible ferric iron, there was no microbial iron reduction, even though the sediments contained high concentrations of oxalate-extractable ferric iron. A correspondence between the presence of hydroxylamine-reducible ferric iron and the extent of ferric iron reduction in anaerobic incubations was observed in sediments from an aquifer and in fresh- and brackish-water sediments from the Potomac River estuary. The assay is a significant improvement over previously described procedures for the determination of hydroxylamine-reducible ferric iron because it provides a correction for the high concentrations of solid ferrous iron which may also be extracted from sediments with acid. This is a rapid...

Availability of Ferric Iron for Microbial Reduction in Bottom Sediments of the Freshwater Tidal Potomac River

Lovley, Derek R.; Phillips, Elizabeth J. P.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1986 EN
Relevância na Pesquisa
579.00477%
The distribution of Fe(III), its availability for microbial reduction, and factors controlling Fe(III) availability were investigated in sediments from a freshwater site in the Potomac River Estuary. Fe(III) reduction in sediments incubated under anaerobic conditions and depth profiles of oxalate-extractable Fe(III) indicated that Fe(III) reduction was limited to depths of 4 cm or less, with the most intense Fe(III) reduction in the top 1 cm. In incubations of the upper 4 cm of the sediments, Fe(III) reduction was as important as methane production as a pathway for anaerobic electron flow because of the high rates of Fe(III) reduction in the 0- to 0.5-cm interval. Most of the oxalate-extractable Fe(III) in the sediments was not reduced and persisted to a depth of at least 20 cm. The incomplete reduction was not the result of a lack of suitable electron donors. The oxalate-extractable Fe(III) that was preserved in the sediments was considered to be in a form other than amorphous Fe(III) oxyhydroxide, since synthetic amorphous Fe(III) oxyhydroxide, amorphous Fe(III) oxyhydroxide adsorbed onto clay, and amorphous Fe(III) oxyhydroxide saturated with adsorbed phosphate or fulvic acids were all readily reduced. Fe3O4 and the mixed Fe(III)-Fe(II) compound(s) that were produced during the reduction of amorphous Fe(III) oxyhydroxide in an enrichment culture were oxalate extractable but were not reduced...

Extracellular Iron Reduction Is Mediated in Part by Neutral Red and Hydrogenase in Escherichia coli

McKinlay, James B.; Zeikus, J. Gregory
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2004 EN
Relevância na Pesquisa
374.98836%
Both microbial iron reduction and microbial reduction of anodes in fuel cells can occur by way of soluble electron mediators. To test whether neutral red (NR) mediates iron reduction, as it does anode reduction, by Escherichia coli, ferrous iron levels were monitored in anaerobic cultures grown with amorphous iron oxide. Ferrous iron levels were 19.4 times higher in cultures fermenting pyruvate in the presence of NR than in the absence of NR. NR did not stimulate iron reduction in cultures respiring with nitrate. To explore the mechanism of NR-mediated iron reduction, cell extracts of E. coli were used. Cell extract-NADH-NR mixtures had an enzymatic iron reduction rate almost 15-fold higher than the chemical NR-mediated iron reduction rate observed in controls with no cell extract. Hydrogen was consumed during stationary phase (in which iron reduction was detectable) especially in cultures containing both NR and iron oxide. An E. coli hypE mutant, with no hydrogenase activity, was also impaired in NR-mediated iron reduction activity. NR-mediated iron reduction rates by cell extracts were 1.5 to 2 times higher with hydrogen or formate as the electron source than with NADH. Our findings suggest that hydrogenase donates electrons to NR for extracellular iron reduction. This process appears to be analogous to those of iron reduction by bacteria that use soluble electron mediators (e.g....

Resistance of Solid-Phase U(VI) to Microbial Reduction during In Situ Bioremediation of Uranium-Contaminated Groundwater

Ortiz-Bernad, Irene; Anderson, Robert T.; Vrionis, Helen A.; Lovley, Derek R.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2004 EN
Relevância na Pesquisa
458.3245%
Speciation of solid-phase uranium in uranium-contaminated subsurface sediments undergoing uranium bioremediation demonstrated that although microbial reduction of soluble U(VI) readily immobilized uranium as U(IV), a substantial portion of the U(VI) in the aquifer was strongly associated with the sediments and was not microbially reducible. These results have important implications for in situ uranium bioremediation strategies.

Advection of surface-derived organic carbon fuels microbial reduction in Bangladesh groundwater

Mailloux, Brian J.; Trembath-Reichert, Elizabeth; Cheung, Jennifer; Watson, Marlena; Stute, Martin; Freyer, Greg A.; Ferguson, Andrew S.; Ahmed, Kazi Matin; Alam, Md. Jahangir; Buchholz, Bruce A.; Thomas, James; Layton, Alice C.; Zheng, Yan; Bostick, Benj
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
471.62906%
Chronic exposure to arsenic (As) by drinking shallow groundwater causes widespread disease in Bangladesh and neighboring countries. The release of As naturally present in sediment to groundwater has been linked to the reductive dissolution of iron oxides coupled to the microbial respiration of organic carbon (OC). The source of OC driving this microbial reduction—carbon deposited with the sediments or exogenous carbon transported by groundwater—is still debated despite its importance in regulating aquifer redox status and groundwater As levels. Here, we used the radiocarbon (14C) signature of microbial DNA isolated from groundwater samples to determine the relative importance of surface and sediment-derived OC. Three DNA samples collected from the shallow, high-As aquifer and one sample from the underlying, low-As aquifer were consistently younger than the total sediment carbon, by as much as several thousand years. This difference and the dominance of heterotrophic microorganisms implies that younger, surface-derived OC is advected within the aquifer, albeit more slowly than groundwater, and represents a critical pool of OC for aquifer microbial communities. The vertical profile shows that downward transport of dissolved OC is occurring on anthropogenic timescales...

Microbial Reduction of Fe(III) under Alkaline Conditions Relevant to Geological Disposal

Williamson, Adam J.; Morris, Katherine; Shaw, Sam; Byrne, James M.; Boothman, Christopher; Lloyd, Jonathan R.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /06/2013 EN
Relevância na Pesquisa
375.10773%
To determine whether biologically mediated Fe(III) reduction is possible under alkaline conditions in systems of relevance to geological disposal of radioactive wastes, a series of microcosm experiments was set up using hyperalkaline sediments (pH ∼11.8) surrounding a legacy lime working site in Buxton, United Kingdom. The microcosms were incubated for 28 days and held at pH 10. There was clear evidence for anoxic microbial activity, with consumption of lactate (added as an electron donor) concomitant with the reduction of Fe(III) as ferrihydrite (added as the electron acceptor). The products of microbial Fe(III) reduction were black and magnetic, and a range of analyses, including X-ray diffraction, transmission electron microscopy, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism confirmed the extensive formation of biomagnetite in this system. The addition of soluble exogenous and endogenous electron shuttles such as the humic analogue anthraquinone-2,6-disulfonate and riboflavin increased both the initial rate and the final extent of Fe(III) reduction in comparison to the nonamended experiments. In addition, a soluble humic acid (Aldrich) also increased both the rate and the extent of Fe(III) reduction. These results show that microbial Fe(III) reduction can occur in conditions relevant to a geological disposal facility containing cement-based wasteforms that has evolved into a high pH environment over prolonged periods of time (>100...

Contrasting Effects of Al Substitution on Microbial Reduction of Fe(III) (Hydr)oxides

Ekstrom, Eileen B.; Learman, Deric R.; Madden, Andrew S.; Hansel Wankel, Colleen M.
Fonte: Meteoritical Society Publicador: Meteoritical Society
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
468.8694%
Aluminum, one of the most abundant elements in soils and sediments, is commonly found co-precipitated with Fe in natural Fe(III) (hydr)oxides; yet, little is known about how Al substitution impacts bacterial Fe(III) reduction. Accordingly, we investigated the reduction of Al substituted (0–13 mol% Al) goethite, lepidocrocite, and ferrihydrite by the model dissimilatory Fe(III)-reducing bacterium (DIRB), Shewanella putrefaciens CN32. Here we reveal that the impact of Al on microbial reduction varies with Fe(III) (hydr)oxide type. No significant difference in Fe(III) reduction was observed for either goethite or lepidocrocite as a function of Al substitution. In contrast, Fe(III) reduction rates significantly decreased with increasing Al substitution of ferrihydrite, with reduction rates of 13% Al-ferrihydrite more than 50% lower than pure ferrihydrite. Although Al substitution changed the minerals’ surface area, particle size, structural disorder, and abiotic dissolution rates, we did not observe a direct correlation between any of these physiochemical properties and the trends in bacterial Fe(III) reduction. Based on projected Al-dependent Fe(III) reduction rates, reduction rates of ferrihydrite fall below those of lepidocrocite and goethite at substitution levels equal to or greater than 18 mol% Al. Given the prevalence of Al substitution in natural Fe(III) (hydr)oxides...

Microbial dissimilatory iron(III) reduction: Studies on the mechanism and on processes of environmental relevance; Mikrobielle dissimilatorische Eisen(III)-Reduktion: Untersuchungen des Mechanismus und verschiedener umweltrelevanter Prozesse

Jahn, Michael
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
479.00477%
Many microbes are able to respire aerobically oxygen or anaerobically other electron acceptors for example sulphate, nitrate, manganese(IV) or Fe(III). As iron minerals are widespread in nature, dissimilatory iron(III) reduction by different microorganisms is a very important process of anaerobic respiration. The general goal of this work was to improve the knowledge of processes, in which iron-reducing microbes are said to play an important role. For this purpose, in one part the focus was made on anaerobic contaminant degradation and in the other part on studies on the mechanism of microbial iron(III) reduction. Both parts were investigated in growth and cell suspension experiments with different microorganisms. At former industrial sites, monoaromatic hydrocarbons, such as benzene, toluene, ethylbenzene, and xylene (BTEX), are widespread contaminants, which cause different problems due to their high solubility in water and strong toxicity. At such sites, where usually anoxic conditions prevail, the anaerobic degradation of these compounds is a very important process. In this study, the anaerobic degradation of BTEX compounds by dissimilatory iron-reducing microorganisms was examined. In order to isolate new bacterial strains, enrichment cultures with the different BTEX compounds added as sole carbon and energy source were prepared. Successful enrichment cultures were obtained for all BTEX substrates both in the presence and absence of AQDS (9...

Microbial iron reduction influenced by humic acids and redox transformation of arsenic by reactive iron minerals; Mikrobielle Eisenreduktion beeinflusst von Huminsäuren und Redoxumwandlung von Arsen durch reaktive Eisenminerale

Amstätter, Katja
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
381.55164%
The work presented in this thesis showed concentration-dependent aggregate formation of 2 line ferrihydrite. Determination of microbial iron reduction rates of Shewanella oneidensis MR 1 in these setups showed limited microbial accessibility of the aggregates depending on the mineral concentration. In addition, the accessibility of the mineral aggregates varied in the presence of different concentrations of humic acids. Adsorbed humic acids changed the surface charge of the mineral aggregates and either lead to further interlinking of the aggregates or repulsion of identically charged particles. Dissolved humic acid in turn can be used by bacteria to transfer electrons to hardly soluble Fe(III) minerals at neutral pH. In particular it was shown that only a very restricted range of dissolved humic acid concentrations (~10-130 mg HA/l) lead to stimulation of microbial iron reduction. Furthermore, the electron transfer properties of humic acids were affected by ionic strength. It was shown that an increase in ionic strength lead to an increase of electrons transferred to Fe(III) by reduced humic acids. In addition to structural changes by electrostatic repulsion between dissolved ions and humic acid we also detected a decrease of particle charge (zeta potential) with increasing ionic strength. This effect may have facilitated interaction between cells and humic acids and enhanced the electron shuttling function of humic acid. In addition to determination of reduction rates...

Enrichment of Members of the Family Geobacteraceae Associated with Stimulation of Dissimilatory Metal Reduction in Uranium-Contaminated Aquifer Sediments

Holmes, Dawn E.; Finneran, Kevin T.; O'Neil, Regina A.; Lovley, Derek R.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /05/2002 EN
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Stimulating microbial reduction of soluble U(VI) to insoluble U(IV) shows promise as a strategy for immobilizing uranium in uranium-contaminated subsurface environments. In order to learn more about which microorganisms might be involved in U(VI) reduction in situ, the changes in the microbial community when U(VI) reduction was stimulated with the addition of acetate were monitored in sediments from three different uranium-contaminated sites in the floodplain of the San Juan River in Shiprock, N.Mex. In all three sediments U(VI) reduction was accompanied by concurrent Fe(III) reduction and a dramatic enrichment of microorganisms in the family Geobacteraceae, which are known U(VI)- and Fe(III)-reducing microorganisms. At the point when U(VI) reduction and Fe(III) reduction were nearing completion, Geobacteraceae accounted for ca. 40% of the 16S ribosomal DNA (rDNA) sequences recovered from the sediments with bacterial PCR primers, whereas Geobacteraceae accounted for fewer than 5% of the 16S rDNA sequences in control sediments that were not amended with acetate and in which U(VI) and Fe(III) reduction were not stimulated. Between 55 and 65% of these Geobacteraceae sequences were most similar to sequences from Desulfuromonas species...