Degradation of BTEX and their aerobic metabolites by indigenous microorganisms under nitrate reducing conditions

1995 ◽  
Vol 31 (1) ◽  
pp. 15-28 ◽  
Author(s):  
P. J. J. Alvarez ◽  
T. M. Vogel
Keyword(s):  
Electron Acceptor ◽  
Nitrate Reduction ◽  
Oxygen Demand ◽  
Toluene Degradation ◽  
Indigenous Microorganisms ◽  
Terminal Electron Acceptor ◽  
Benzene Degradation ◽  
Reducing Conditions ◽  
Anaerobic Benzene Degradation ◽  
Benzene Toluene

Batch incubations, seeded with four different aquifer materials, were used to survey the catabolic capacity of indigenous microorganisms under nitrate reducing conditions. Benzene, toluene, ethylbenzene, xylenes (BTEX), and selected potential metabolites of their incomplete aerobic degradation, were tested as substrates for nitrate-based respiration. Toluene and its potential aerobic metabolites, benzoate, protocatechuate, 3-methylcatechol, 4-methylcatechol, succinate, and adipate were degraded in strictly anoxic (O2 < 0.1 mg/l) nitrate reducing incubations. Toluene degradation was directly coupled to nitrate reduction. Ortho-xylene removal was toluene dependent. Meta- and para-xylenes were degraded in nitrate reducing enrichments from only one of the four aquifer samples. Benzene, ethylbenzene, catechol and gentisate were not degraded within up to four months in any of the incubations, even though nitrate reduction occurred. Anaerobic benzene degradation was not observed. Incubations receiving nitrate as an adjunct electron acceptor to oxygen degraded significantly more benzene than incubations amended with only oxygen, although benzene was only degraded until the dissolved oxygen was depleted. Possibly, more oxygen was available to degrade benzene when nitrate was added because denitrifiers utilizing nitrate as terminal electron acceptor oxidized benzoate, which had been added to increase the biochemical oxygen demand of the system. Benzoate oxidation with nitrate apparently spared oxygen for benzene degradation.

scholarly journals Anaerobic Degradation of Benzene, Toluene, Ethylbenzene, and Xylene Compounds by Dechloromonas Strain RCB

2005 ◽  
Vol 71 (12) ◽  
pp. 8649-8655 ◽  
Author(s):  
Romy Chakraborty ◽  
Susan M. O'Connor ◽  
Emily Chan ◽  
John D. Coates
Keyword(s):  
Electron Acceptor ◽  
Nitrate Reduction ◽  
Anaerobic Degradation ◽  
Electron Donors ◽  
Metabolic Versatility ◽  
Potential Applicability ◽  
Benzene Toluene ◽  
Total Hydrocarbons ◽  
Unidentified Metabolite

ABSTRACT Dechloromonas strain RCB has been shown to be capable of anaerobic degradation of benzene coupled to nitrate reduction. As a continuation of these studies, the metabolic versatility and hydrocarbon biodegradative capability of this organism were investigated. The results of these revealed that in addition to nitrate, strain RCB could alternatively degrade benzene both aerobically and anaerobically with perchlorate or chlorate [(per)chlorate] as a suitable electron acceptor. Furthermore, with nitrate as the electron acceptor, strain RCB could also utilize toluene, ethylbenzene, and all three isomers of xylene (ortho-, meta-, and para-) as electron donors. While toluene and ethylbenzene were completely mineralized to CO2, strain RCB did not completely mineralize para-xylene but rather transformed it to some as-yet-unidentified metabolite. Interestingly, with nitrate as the electron acceptor, strain RCB degraded benzene and toluene concurrently when the hydrocarbons were added as a mixture and almost 92 μM total hydrocarbons were oxidized within 15 days. The results of these studies emphasize the unique metabolic versatility of this organism, highlighting its potential applicability to bioremediative technologies.

scholarly journals Hydroxylation and Carboxylation—Two Crucial Steps of Anaerobic Benzene Degradation by Dechloromonas Strain RCB

2005 ◽  
Vol 71 (9) ◽  
pp. 5427-5432 ◽  
Author(s):  
Romy Chakraborty ◽  
John D. Coates
Keyword(s):  
Activation Energy ◽  
Addition Reaction ◽  
Hydroxyl Group ◽  
Hydrocarbon Biodegradation ◽  
Terminal Electron Acceptor ◽  
Benzene Degradation ◽  
Anaerobic Benzene Degradation ◽  
Fuel Oils ◽  
Fumarate Addition ◽  
Recent Attention

ABSTRACT Benzene is a highly toxic industrial compound that is essential to the production of various chemicals, drugs, and fuel oils. Due to its toxicity and carcinogenicity, much recent attention has been focused on benzene biodegradation, especially in the absence of molecular oxygen. However, the mechanism by which anaerobic benzene biodegradation occurs is still unclear. This is because until the recent isolation of Dechloromonas strains JJ and RCB no organism that anaerobically degraded benzene was available with which to elucidate the pathway. Although many microorganisms use an initial fumarate addition reaction for hydrocarbon biodegradation, the large activation energy required argues against this mechanism for benzene. Other possible mechanisms include hydroxylation, carboxylation, biomethylation, or reduction of the benzene ring, but previous studies performed with undefined benzene-degrading cultures were unable to clearly distinguish which, if any, of these alternatives is used. Here we demonstrate that anaerobic nitrate-dependent benzene degradation by Dechloromonas strain RCB involves an initial hydroxylation, subsequent carboxylation, and loss of the hydroxyl group to form benzoate. These studies provide the first pure-culture evidence of the pathway of anaerobic benzene degradation. The outcome of these studies also suggests that all anaerobic benzene-degrading microorganisms, regardless of their terminal electron acceptor, may use this pathway.

scholarly journals Nitrate reduction stimulates and is stimulated by phenazine-1-carboxylic acid oxidation by Citrobacter portucalensis MBL

2021 ◽  
Author(s):  
Lev M Tsypin ◽  
Dianne K. Newman
Keyword(s):  
Carboxylic Acid ◽  
Nitrate Reductase ◽  
Electron Acceptor ◽  
Nitrate Reduction ◽  
Redox Activity ◽  
Acid Oxidation ◽  
Dependent Manner ◽  
Redox Cycle ◽  
Terminal Electron Acceptor ◽  
Genetically Determined

Phenazines are secreted metabolites that microbes use in diverse ways, from quorum sensing to antimicrobial warfare to energy conservation. Phenazines are able to contribute to these activities due to their redox activity. The physiological consequences of cellular phenazine reduction have been extensively studied, but the counterpart phenazine oxidation has been largely overlooked. Phenazine-1-carboxylic acid (PCA) is common in the environment and readily reduced by its producers. Here, we describe its anaerobic oxidation by Citrobacter portucalensis strain MBL, which was isolated from topsoil in Falmouth, MA, and which does not produce phenazines itself. This activity depends on the availability of a suitable terminal electron acceptor, specifically nitrate. When C. portucalensis MBL is provided reduced PCA and nitrate, it rapidly oxidizes the PCA. We compared this terminal electron acceptor-dependent PCA-oxidizing activity of C. portucalensis MBL to that of several other γ-proteobacteria with varying capacities to respire nitrate. We found that PCA oxidation by these strains in a nitrate-dependent manner is decoupled from growth and correlated with their possession of the periplasmic nitrate reductase Nap. We infer that bacterial PCA oxidation is widespread and propose that it may be genetically determined. Notably, oxidizing PCA enhances the rate of nitrate reduction to nitrite by C. portucalensis MBL beyond the stoichiometric exchange of electrons from PCA to nitrate, which we attribute to C. portucalensis MBL's ability to also reduce oxidized PCA, thereby catalyzing a complete PCA redox cycle. This bidirectionality highlights the versatility of PCA as a biological redox agent.

scholarly journals Bidirectional redox cycling of phenazine-1-carboxylic acid by Citrobacter portucalensis MBL drives increased nitrate reduction

2020 ◽  
Author(s):  
Lev M. Tsypin ◽  
Dianne K. Newman
Keyword(s):  
Carboxylic Acid ◽  
Electron Acceptor ◽  
Nitrate Reduction ◽  
Redox Cycling ◽  
Redox Activity ◽  
Dependent Manner ◽  
Terminal Electron Acceptor ◽  
Anoxic Environments ◽  
Redox Active ◽  
Oxygen Starvation

ABSTRACTPhenazines are secreted metabolites that microbes use in diverse ways, from quorum sensing to antimicrobial warfare to energy conservation. Phenazines are able to contribute to these activities due to their redox activity. The physiological consequences of cellular phenazine reduction have been extensively studied, but the counterpart phenazine oxidation has been largely overlooked. Phenazine-1-carboxylic acid (PCA) is common in the environment and readily reduced by its producers. Here, we describe its anaerobic oxidation by Citrobacter portucalensis strain MBL, which was isolated from topsoil in Falmouth, MA, and which does not produce phenazines itself. This activity depends on the availability of a suitable terminal electron acceptor, specifically nitrate or fumarate. When C. portucalensis MBL is provided reduced PCA and either nitrate or fumarate, it continuously oxidizes the PCA. We compared this terminal electron acceptor-dependent PCA-oxidizing activity of C. portucalensis MBL to that of several other γ-proteobacteria with varying capacities to respire nitrate and/or fumarate. We found that PCA oxidation by these strains in a fumarate-or nitrate-dependent manner is decoupled from growth and correlated with their possession of the fumarate or periplasmic nitrate reductases, respectively. We infer that bacterial PCA oxidation is widespread and genetically determined. Notably, reduced PCA enhances the rate of nitrate reduction to nitrite by C. portucalensis MBL beyond the stoichiometric prediction, which we attribute to C. portucalensis MBL’s ability to also reduce oxidized PCA, thereby catalyzing a complete PCA redox cycle. This bidirectionality highlights the versatility of PCA as a biological redox agent.IMPORTANCEPhenazines are increasingly appreciated for their roles in structuring microbial communities. These tricyclic aromatic molecules have been found to regulate gene expression, be toxic, promote antibiotic tolerance, and promote survival under oxygen starvation. In all of these contexts, however, phenazines are studied as electron acceptors. Even if their utility arises primarily from being readily reduced, they would need to be oxidized in order to be recycled. While oxygen and ferric iron can oxidize phenazines abiotically, biotic oxidation of phenazines has not been studied previously. We observed bacteria that readily oxidize phenazine-1-carboxylic acid (PCA) in a nitrate-dependent fashion, concomitantly increasing the rate of nitrate reduction to nitrite. Because nitrate is a prevalent terminal electron acceptor in diverse anoxic environments, including soils, and phenazine-producers are widespread, this observation of linked phenazine and nitrogen redox cycling suggests an underappreciated role for redox-active secreted metabolites in the environment.

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).

Rates and potential mechanism of anaerobic nitrate-dependent microbial pyrite oxidation

2012 ◽  
Vol 40 (6) ◽  
pp. 1280-1283 ◽  
Author(s):  
Julian Bosch ◽  
Rainer U. Meckenstock
Keyword(s):  
Electron Acceptor ◽  
Pyrite Oxidation ◽  
Laboratory Data ◽  
Laboratory Studies ◽  
Mineral Phase ◽  
Terminal Electron Acceptor ◽  
Micro Organisms ◽  
Open Question ◽  
Sulfur Containing ◽  
Positive Results

Pyrite (FeS2) is a major iron- and sulfur-containing mineral phase in the environment. Oxidation of pyrite by aerobic micro-organisms has been well investigated. However, the reactivity of pyrite under anoxic conditions is still an open question. In the present paper, we summarize field and laboratory data on this chemolithotrophic respiration process with nitrate as terminal electron acceptor. Geochemical and stable isotope field data indicate that this process is occurring. Laboratory studies are more ambiguous, but recent positive results provide evidence that anaerobic microbial pyrite oxidation can, in fact, occur with nitrate as electron acceptor.

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