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At least 127 records · Page 7Linked to original sources
PubMed2005

Metabolism of fluoranthene by mycobacterial strains isolated by their ability to grow in fluoranthene or pyrene.

Mycobacterium sp. strains CP1, CP2, CFt2 and CFt6 were isolated from creosote-contaminated soil due to their ability to grow in pyrene (CP1 and CP2) or fluoranthene (CFt2 and CFt6). All these strains utilized fluoranthene as a sole source of carbon and energy. Strain CP1 exhibited the best growth, with a cellular assimilation of fluoranthene carbon of approximately 45%. Identification of the metabolites accumulated during growth in fluoranthene, the kinetics of metabolites, and metabolite feeding studies, indicated that all these isolates oxidized fluoranthene by the following two routes: the first involves dioxygenation at C-1 and C-2, meta cleavage, and a 2-carbon fragment excision to produce 9-fluorenone-1-carboxylic acid. An angular dioxygenation of the latter yields cis-1,9a-dihydroxy-1-hydrofluorene-9-one-8-carboxylic acid, which is further degraded via 8-hydroxy-3,4-benzocoumarin-1-carboxylic acid, benzene-1,2,3-tricarboxylic acid, and phthalate; the second route involves dioxygenation at C-2 and C-3 and ortho cleavage to give Z-9-carboxymethylenefluorene-1-carboxylic acid. In addition, the pyrene-degrading strains CP1 and CP2 possess a third route initiated by dioxygenation at positions C-7 and C-8, which--following meta cleavage, an aldolase reaction, and a C(1)-fragment excision--yields acenaphthenone. Monooxygenation of this ketone to the corresponding quinone, and its subsequent hydrolysis, produces naphthalene-1,8-dicarboxylic acid. The results obtained in this study not only complete and confirm the three fluoranthene degradation routes previously proposed for the pyrene-degrading strain Mycobacterium sp. AP1, but also suggest that such routes represent general microbial processes for environmental fluoranthene removal.

Biodegradation, Environmental↗
PubMed2001

Litterfall and organic matter decomposition in a seasonal forest of the eastern Chaco (Argentina).

Amazonia and the Gran Chaco are the largest phytogeographic units of the Neotropical Region. The Forest Wedge of the Santa Fe province of Argentina is the southernmost part of the Eastern Chaco, and there are three main types of forest, 1) the mixed dense forests, 2) the Schinopsis balansae "quebrachal" and 3) the Prosopis nigra var. ragonesei forests, distributed along an environmental gradient correlated with topographic elevation. In this paper litterfall and organic matter decomposition of four species were studied in two different microsites in a Schinopsis balansae forest during three years. Litter fall varied along the year following seasonal environmental variation but litterfall variations between years were not significant. Litterfall was not uniform over the whole surface, under close canopy monthly average litterfall amounts 32.67 g/m2, in open gaps 4.47 g/m2 and 15.07 g/m2 under medium density canopy. Organic matter decomposition, like in other forests, was a negative exponential function of time, and the decomposition rate is independent from the microsites where it falls, 0.15 and 0.12 in sunny and shadow microsites respectively for Maytenus vitis-idaea, 0.10 and 0.11 in sunny and shadow microsites respectively for Achatocarpus praecox, 0.04 and 0.03 for Acacia praecox, 0.04 and 0.06 for Schinopsis balansae in sunny and shadow microsites respectively. Shurbs litter was decomposed faster than the tree litter, and the shurbs litter nutrientes level was also higher. Therefore the rate of organic matter decomposition is more correlated with leaf characteristics than with environmental variables.

Argentina↗
PubMed1989

[Hydraulo-geologic assumptions of biological purification processes in the subsoil].

The use of microbiological methods to remediate contaminated underground and ground water may become both effective and economically advantageous. To exploit the potential advantage of these methods, one must start early enough prior to the treatment investigate the degradability of the contaminants present, and the geo-hydraulic conditions existing at the site. It seem to be advisable to involve neutral experts at this stage of preparation, i.e., those who are personally not indebted to one specific remediation method. At the present time, the progress in the biological remediation techniques seems to allow their use in numerous cases of the environmental contamination under economically attractive conditions.

Bacteria↗
PubMed2026

Discovering hidden candidate plastic-degrading enzymes: Combined multi-omics and machine learning strategy.

Plastic pollution poses a major threat to the stability of natural ecosystems as well as human health. Microbial enzymes have long been considered a potential resource for targeted biodegradation but, except for a few successful cases, the discovery of efficient enzymes has proved challenging. Aiming to accelerate the process, we propose an approach combining metagenomics, metatranscriptomics and semi-supervised learning that selects promising plastic-degrading candidate enzymes from the proteome of relevant microorganisms. Tested on a dataset of over 10,000 microbial proteins, ranking models consistently prioritize known plastic-degrading enzymes, achieving an area under the cumulative distribution function curve above 0.96, with leave-one-family-out cross-validation indicating that performance is largely retained across protein families. As a case study, this work focuses on mixed microbial cultures exposed for extended periods to polyethylene, polyethylene terephthalate, and polyurethane substrates. The prevalent species after selective enrichment were functionally characterized, finding Rhodococcus aetherivorans as the most relevant species in two of the five cultures under investigation. Among the top-ranked proteins, several have high structural similarity with known enzymes despite not being identified by sequence similarity search. Moreover, according to metatranscriptomics results, several of these enzymes were found to be expressed at the same level or above that of annotated enzymes, suggesting that they may have functional relevance. Overall, this work highlights the potential of integrating multi-omics with data-driven methods for enzyme discovery and for accelerating the development of biotechnological solutions to plastic pollution.

Biodegradation, Environmental↗
PubMed2001

Fate, effects and potential environmental risks of ethylene glycol: a review.

The fate, effects, and potential environmental risks of ethylene glycol (EG) in the environment were examined. EG undergoes rapid biodegradation in aerobic and anaerobic environments (approximately 100% removal of EG within 24 h to 28 days). In air, EG reacts with photo-chemically produced hydroxyl radicals with a resulting atmospheric half-life of 2 days. Acute toxicity values (LC(50)s and EC(50)s) were generally >10,000 mg/l for fish and aquatic invertebrates. The data collectively show that EG is not persistent in air, surface water, soil, or groundwater, is practically non-toxic to aquatic organisms, and does not bioaccumulate in aquatic organisms. Potential long-term, quasi-steady state regional concentrations of EG estimated with a multi-media model for air, water, soil, and sediment were all less than predicted no effect concentrations (PNECs).

Amphibians↗
PubMed1997

Factors affecting atrazine fate in north central U.S. soils.

Atrazine persistence and fate are influenced by many factors, the interactions of which are difficult to predict. Several models, such as LEACHP (Wagenet and Hutson 1989), have been used as tools to estimate losses and identify variables that will impact the magnitude of loss. The LEACHP model was evaluated for predicting atrazine movement in sandy loam, silt loam, and clay loam soils during three consecutive years (two dry and one wet) in Minnesota (Khakural et al. 1995). Considering the broad range in soil properties and climatic conditions used in testing, the model performed well. However, these are only estimates, and additional field studies need to be conducted to verify model results. In a report by Fausey et al. (1995), the amount of atrazine found in groundwater throughout the Midwestern region was reported to be much below the MCL. However, specific sites in the Midwest may struggle with atrazine problems from both point and nonpoint sources of contamination. Some states, such as South Dakota, have created groundwater protection areas that alert growers and the public to sensitive areas where contamination may occur because of soil type, depth to groundwater, and distance to public wellheads. Wisconsin has developed a tiered managerial strategy, or zoning approach, in which restrictions are matched to pollution detections (Wolf and Nowak 1996). The USEPA has mandates for states to implement generic management plans to prevent pesticide contamination of groundwater. Chemical-specific plans by states will be required for at least five pesticides, one of which will be atrazine. Best management practices have been and are continuing to be developed to aid the grower in lessening the adverse impacts of atrazine. With continuing research into understanding the problem and developing solutions, and with adaptation of these recommendations by growers, the use of effective, inexpensive herbicides may continue with minimal off-site environmental effects.

Agriculture↗
PubMed2006

Mechanism of augmentation of organotin decomposition by ferripyochelin: formation of hydroxyl radical and organotin-pyochelin-iron ternary complex.

Pyochelin (PCH), a kind of siderophore secreted by Pseudomonas aeruginosa, was recently found to have triphenyltin (TPT)-decomposing capacity. In this work, significant augmentation of TPT decomposition by ferripyochelin (FePCH), the chelating compound of PCH with iron, was demonstrated in Tris-HCl buffer (pH 8.0). The generation of hydroxyl radical (HO.) in the presence of FePCH was observed. Inhibition of HO. generation by adding catalase and HO. scavengers (methanol and dimethyl sulfoxide) decreased TPT decomposition, while an increase in HO. formation in the presence of H(2)O(2) enhanced its decomposition. Our findings indicated that HO. generated in the reaction system was responsible for the enhanced TPT decomposition by FePCH versus PCH. The existence of the TPT-pyochelin-iron ternary complex was demonstrated by electron spray ionization-mass spectrometry, tandem mass spectrometry, and (1)H nuclear magnetic resonance. On the basis of the above results, HO. produced in the presence of FePCH was deduced to be in close proximity to TPT and has more opportunity to attack the Sn-C bond, which resulted in the enhanced organotin decomposition. The information obtained may have considerable environmental significance.

Biodegradation, Environmental↗
PubMed1983

Metabolism of fensulfothion by a soil bacterium, Pseudomonas alcaligenes C1.

Fensulfothion (O,O-diethyl O-[4-(methylsulfinyl)phenyl]phosphorothioate), an organophosphorus pesticide used to control the golden nematode Heterodera rostochiensis, is used as a source of carbon by microorganisms isolated from soils treated with the pesticide. Two of the microbial isolates, Pseudomonas alcaligenes C1 and Alcaligenes sp. strain NC3, used more than 80% of the pesticide in 120 h in culture when supplemented as a source of carbon. P. alcaligenes C1, which showed maximal growth on fensulfothion, degraded the compound to p-methylsulfinyl phenol and diethyl phosphorothioic acid. The phenolic metabolite could be identified by conventional spectral analysis, whereas the spectral patterns of the phosphorus-containing metabolite suggested that the compound was complexed with some cellular molecules. However, utilization of the phosphoric acid ester and ethanol by P. alcaligenes C1 suggested that the microbe attacks fensulfothion by an initial hydrolysis of the compound and subsequent utilization of the phosphoric acid ester. The pathway of degradation of fensulfothion by P. alcaligenes is of great value in the detoxification of the pesticide residues and also in the environmentally stable phosphoric acid esters.

Biodegradation, Environmental↗
PubMed2003

Combination of microautoradiography and fluorescence in situ hybridization for identification of microorganisms degrading xenobiotic contaminants.

One of the central topics in environmental bioremediation research is to identify microorganisms that are capable of degrading the contaminants of interest. Here we report application of combined microautoradiography (MAR) and fluorescence in situ hybridization (FISH). The method has previously been used in a number of systems; however, here we demonstrate its feasibility in studying the degradation of xenobiotic compounds. With a model system (coculture of Pseudomonas putida B2 and Sphingomonas stygia incubated with [14C] o-nitrophenol), combination of MAR and FISH was shown to be able to successfully identify the microorganisms degrading o-nitrophenol. Compared with the conventional techniques, MAR-FISH allows fast and accurate identification of the microorganisms involved in environmental contaminant degradation.

Autoradiography↗
PubMed2005

Application of constructed wetlands to the treatment of leachates from a municipal solid waste landfill in Ibadan, Nigeria.

Leachates are wastewater generated principally from landfills and solid waste disposal sites. Leachates emanating from municipal wastes are a major source of surface and groundwater pollution worldwide. Globally, leachates have been implicated in low yield of farm produce, developmental anomalies, low birth weights, leukemia incidence, and other cancers in communities around the site. They have also been implicated in hazards to the environment, loss of biodiversity, and contamination of water sources. At Aba-Eku in Nigeria, leachates are being discharged into the Omi Stream without treatment. A study was conducted on a method of leachate treatment that passes the leachate through constructed wetlands using Ipomoea aquatica (Forsk), a locally available plant found close to the landfill site. The aim of the study was to evolve a sustainable and cost-effective method of treatment whose effluents can be discharged into the Omi Stream with no or minimal impact. The study was descriptive and analytical in design. Samples were collected and analyzed with standard methods for pH, suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia, nitrate, and trace metals. Raw leachates were turbid and amber in color and contained suspended solids (197.5 mg/L), ammonia (610.9 mg/L), lead (1.64 mg/L), iron (198.10 mg/L), and manganese (23.20 mg/L). When the leachates were passed through the constructed wetland with eight hours' detention time, effluents showed significant reductions in suspended solids (81.01 percent), BOD (86.03 percent), and ammonia (97.77 percent). The study shows that a constructed wetland is a feasible tool for the treatment of leachates before their disposal into the environment in Nigeria and can help safeguard environmental quality.

Ammonia↗
PubMed1995

Use of a polymerase-chain-reaction-amplified DNA probe from Pseudomonas putida to detect D-hydantoinase-producing microorganisms by direct colony hybridization.

Pseudomonas putida strain DSM 84 produces N-carbamyl-D-amino acids from the corresponding D-5-monosubstituted hydantoins. The sequence of the D-hydantoinase gene from this strain (GenBank accession number L24157) was used to develop a DNA probe of 122 base pairs (bp) that could detect D-hydantoinase genes in other bacterial genera by DNA and by colony hybridization. Under conditions tolerating 32% mismatch, the probe was specific for all strains that expressed D-hydantoinase activity. These include Pseudomonadaceae of all rRNA groups, and bacteria belonging to the genera Agrobacterium, Serratia, Corynebacterium, and Arthrobacter. Environmental sampling was simulated by screening a mixture of unknown microorganisms from commercial inocula for the biodegradation of industrial, municipal and domestic wastes. The 122-bp probe was specific for microorganisms that subsequently demonstrated D-hydantoinase activity. Bacterial species from four different genera were detected, which were Pseudomonas, Klebsiella, Enterobacter, and Enterococcus.

Amidohydrolases↗
PubMed2026

Towards microplastic bioremediation: Fungal degradation of pristine and pretreated high-density polyethylene and polystyrene.

Microplastic (MP) contamination has become a significant ecological issue because of its enduring existence in the ecosystem and its possible negative impacts. Therefore, using degrading strategies to eliminate these stubborn polymers has been a subject of scientific research. However, the currently used degradation methods are relatively inefficient. Given the pervasiveness of High-Density Polyethylene (HDPE) and Polystyrene (PS) and their resistance to biodegradability, disposal strategies are critical and must be addressed. This manuscript examines the biodegradation of pristine and UV-treated HDPE and PS MPs by Aspergillus flavus species in minimal growth media over 70 days. The maximum weight loss observed at 70 days for pristine HDPE and PS in sole carbon source (SCS) media was (29.33 ± 0.28) % and (17.67 ± 0.35) %, respectively. Whereas, for UV-treated HDPE and PS MPs, the % weight reduction was (33 ± 0.21) % and (25 ± 0.19) %, respectively. UV-treated MPs exhibited greater weight reduction, as UV induced oxygenated functional groups enhance polymer susceptibility to enzymes, thereby promoting biodegradation. HDPE MPs typically show a higher proportion of particles in the lower size range compared to PS MPs. This assertion was based on the weight loss, particle size distribution, and SEM analysis. Furthermore, chemical changes were evaluated using Fourier transform Infrared Spectroscopy (FTIR) analysis, which also displayed chemical oxidation occurring during biodegradation. Liquid Chromatography-Mass Spectrometry (LC-MS) results indicate that UV pretreatment enhances biodegradability by promoting chain scission. These findings further suggest that this fungus's natural and ubiquitous occurrence in terrestrial and marine environments may actively contribute to MP biodegradation while requiring few nutrients.

Microplastics↗
PubMed2001

Degradation of diphenyl ether herbicides by the lignin-degrading basidiomycete Coriolus versicolor.

Under ligninolytic conditions, the white-rot basidiomycete Coriolus versicolor metabolized chloronitrofen (2, 4, 6-trichloro-4'-nitrodiphenyl ether; CNP) and nitrofen (2, 4-dichloro-4'-nitrodiphenyl ether, NIP), which constitute the largest class of commercially produced diphenyl ether herbicides. The pathway of CNP degradation was elucidated by the identification of fungal metabolites upon addition of CNP and its metabolic intermediates. The metabolic pathway was initially branched to form four metabolites--2, 4, 6-trichloro-3-hydroxy-4'-nitrodiphenyl ether, 2, 4-dichloro-6-hydroxy-4'-nitrodiphenyl ether, NIP, and 2, 4, 6-trichloro-4'-aminodiphenyl ether--indicating the involvement of hydroxylation, oxidative dechlorination, reductive dechlorination, and nitro-reduction. Of these reactions, hydroxylation was relatively major compared to the others. Extracellular ligninolytic enzymes such as lignin peroxidase, manganese peroxidase and laccase did not catalyze the oxidation of either CNP or NIP. Piperonyl butoxide, an inhibitor of cytochrome P450, suppressed fungal oxidation of CNP and NIP to their hydroxylated products. The inhibition resulted in increasing the amount of reductively dechlorinated and nitro-reduced products. These observations strongly suggest that basidiomycetes may possess a mechanism for a strict substrate recognition system and a corresponding metabolic response system to effectively degrade environmentally persistent aromatic compounds.

Basidiomycota↗
PubMed2007

Biosurfactant production by antarctic facultative anaerobe Pantoea sp. during growth on hydrocarbons.

The facultative anaerobe Pantoea sp. strain A-13, isolated from ornithogenic soil of Dewart Island (Frazier Islands), Antarctica, produced glycolipid biosurfactants when grown on n-paraffins or kerosene as the sole source of carbon and energy. Hemolysis of erythrocytes, growth inhibition of Bacillus subtilis, and thin-layer chromatography studies have suggested that the secreted glycolipids are rhamnolipids. Glycolipids produced by kerosene-grown cells decreased the surface tension at the air-water interface to 30 mN/m and possessed a low critical micelle concentration value of 40 mg/l, which indicated high surface activity. They efficiently emulsified aromatic hydrocarbons, kerosene, and n-paraffins. Biosurfactant production contributed to an increase in cell hydrophobicity, which correlated with increased growth of the strain on tested hydrocarbons. According to the results, the Antarctic biosurfactant-producing strain Pantoea sp. A-13 appears to be valuable source for application in accelerated environmental bioremediation.

Anaerobiosis↗
PubMed2005

Microbiological degradation of pentane by immobilized cells of Arthrobacter sp.

The increasing production of several plastics such as expanded polystyrene, widely used as packaging and building materials, has caused the release of considerable amounts of pentane employed as an expanding agent. Today many microorganisms are used to degrade hydrocarbons in order to minimize contamination caused by several industrial activities. The aim of our work was to identify a suitable microorganism to degrade pentane. We focused our attention on a strain of Arthrobacter sp. which in a shake-flask culture produced 95% degradation of a 10% mixture of pentane in a minimal medium after 42 days of incubation at 20 degrees C. Arthrobacter sp. cells were immobilized on a macroporous polystyrene particle matrix that provides a promising novel support for cell immobilization. The method involved culturing cells with the expanded polystyrene in shake-flasks, followed by in situ growth within the column. Scanning electron microscopy analysis showed extensive growth of Arthrobacter sp. on the polymeric surface. The immobilized microorganism was able to actively degrade a 10% mixture of pentane, allowing us to obtain a bioconversion yield of 90% after 36 h. Moreover, in repeated-batch operations, immobilized Arthrobacter sp. cells were able to maintain 85-95% pentane degradation during a 2 month period. Our results suggest that this type of bioreactor could be used in pentane environmental decontamination.

Arthrobacter↗