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At least 127 records · Page 7Linked to original sources
PubMed2004

Influence of the stabilisation of organic materials on their biopesticide effect in soils.

Some organic materials have shown a suppressive effect on several diseases induced by soilborne plant pathogens. We have carried out a laboratory experiment (microcosm) to ascertain the influence of the stabilisation process of sewage sludge on it biopesticide effect when Pythium ultimum or Phytophthora sp. were introduced to soil as pathogens for pea or pepper. When P. ultimum was introduced there was a 63.8% reduction in the weight of the stems grown in the control, 47.6% in the presence of sewage sludge, but only 24.7% with compost. The same biopesticide effect was evident from the weight of the roots. The biopesticide effect was also strong when compost was used as organic amendment in the presence of Phytophthora, as could be seen from stem and shoot weight and length. The data showed that the degree of stabilisation of the organic material (compost) had a positive influence on it biopesticide effect. The changes undergone by a soil after the addition of organic materials helped to explain the biopesticide effect of the amendment. The organic treatments reduced P. ultimum and Phytophthora sp. populations.

Analysis of Variance↗
PubMed2005

Calcium carbonate formation by Synechococcus sp. strain PCC 8806 and Synechococcus sp. strain PCC 8807.

Precipitation of CaCO3 catalyzed by the growth and physiology of cyanobacteria in the genus Synechococcus represents a potential mechanism for sequestration of atmospheric CO2 produced during the burning of coal for power generation. Synechococcus sp. strain PCC 8806 and Synechococcus sp. strain PCC 8807 were tested in microcosm experiments for their ability to calcify when exposed to a fixed calcium concentration of 3.4 mM and dissolved inorganic carbon concentrations of 0.5, 1.25 and 2.5 mM. Synechococcus sp. strain PCC 8806 removed calcium continuously over the duration of the experiment producing approximately 18.6 mg of solid phase calcium. Calcium removal occurred over a two-day time period when Synechococcus sp. strain PCC 8807 was tested and only 8.9 mg of solid phase calcium was produced. Creation of an alkaline growth environment catalyzed by the physiology of the cyanobacteria appeared to be the primary factor responsible for CaCO3 precipitation in these experiments.

Bicarbonates↗
PubMed2006

Depuration of microcystins in tilapia fish exposed to natural populations of toxic cyanobacteria: a laboratory study.

Previous studies demonstrated that microcystins (MCYSTs) can be accumulated in different organs, particularly the liver, of tilapia fish (Oreochromis niloticus) in an Egyptian fish farm containing toxic blooms of Microcystis aeruginosa. In the present study, a microcosm experiment was conducted to examine the depuration of MCYSTs in tilapia fish from this fish farm. Fish were grown in a 100-L aerated recirculation tank containing dechlorinated water at room temperature (25+/-2 degrees C) for 96 h. MCYST concentrations in livers, intestines, and gallbladders of each daily sacrificed fish were determined by both enzyme-linked immunosorbent assay (ELISA) and protein phosphatase inhibition assay (PPIA). MCYST concentrations in the surrounding water were also determined by the same methods. The results showed that MCYST concentrations in the liver and intestine decreased gradually throughout the experimental period. This decrease was accompanied by an increase in MCYST concentrations in the gallbladder and surrounding water. The maximum value of MCYST in the surrounding water was obtained after 96 h at a level of 1.2 microg/L by ELISA, while it was obtained after 24 h at a level of 0.5 microg/L by PPIA and remained stable until the end of the experiment. The present study revealed that tilapia fish can depurate and excrete MCYSTs into the bile and surrounding water as a way to avoid toxicity from such a potent hepatotoxin.

Animals↗
PubMed2004

Bioremediation of coastal areas 5 years after the Nakhodka oil spill in the Sea of Japan: isolation and characterization of hydrocarbon-degrading bacteria.

Five years after the 1997 Nakhodka oil spill in the Sea of Japan, seven bacterial strains capable of utilizing the heavy oil spilled from the Nakhodka Russian oil tanker were isolated from three coastal areas (namely Katano Seashore of Fukui Prefecture, Osawa and Atake seashores of Ishikawa Prefecture) and the Nakhodka Russian oil tanker after a 5-year bioremediation process. All bacterial strains isolated could utilize long-chain-length alkanes efficiently, but not aromatic, and all of them were able to grow well on heavy oil. Using 16S rDNA sequencing, most of the strains were affiliated to Pseudomonas aeruginosa. Comparing between the year 1997 (at the beginning of bioremediation process) and the year 2001 (after 5 years of bioremediation), there was no significant change in morphology and size of hydrocarbon-degrading bacteria during the 5-year bioremediation. Scanning and transmission electron microscopic observations revealed that a large number of hydrocarbon-degrading bacteria still existed in the sites consisting of a variety of morphological forms of bacteria, such as coccus (Streptococcus and Staphylococcus) and bacillus (Streptobacillus). On the application of bioremediation processes on the laboratory-scale, laboratory microcosm experiments (containing seawater, beach sand, and heavy oil) under aerobic condition by two different treatments (i.e., placed the inside building and the outside building) were established for bioremediation of heavy oil to investigate the significance of the role of hydrocarbon-degrading bacteria on them. There was no significant bacterial activity differentiation in the two treatments, and removal of heavy oil by hydrocarbon-degrading bacteria in the outside building was slightly greater than that in the inside building. The values of pH, Eh, EC, and dissolved oxygen (DO) in two treatments indicated that the bioremediation process took place under aerobic conditions (DO: 1-6 mg/l; Eh: 12-300 mV) and neutral-alkaline conditions (pH 6.4-8) with NaCl concentrations of 3-15% (ECs of 45-200 mS/cm).

Bacteria↗
PubMed2004

The uptake of uranium by Eleocharis dulcis (Chinese water chestnut) in the Ranger Uranium Mine constructed wetland filter.

Eleocharis dulcis has proliferated in a constructed wetland used to treat uranium mine runoff water, where it rapidly accumulates significant quantities of uranium (U) in its roots and relatively little in its stems. We investigated the mechanism of U uptake and accumulation by E. dulcis using field-sampling techniques and microcosm test work. Results from the microcosm trials and outcomes from statistical tests of field sampled macrophyte, water and sediment indicate that the primary source of U for E. dulcis is the water column. Basipetal translocation of U to the plant's roots was indicated by significant correlations between the U content of stems, taproots and rhizomes and XPS detection of U inside root segments. U sequestering from sediment interstitial water by Fe hydroxides on root surfaces was also evident. No basipetal translocation was evident following the 28-day duration of the microcosm experiments, indicating that it is a longer-term process.

Biodegradation, Environmental↗
PubMed2005

Structural and functional diversity of microbial communities from a lake sediment contaminated with trenbolone, an endocrine-disrupting chemical.

Effects of trenbolone (TBOH), a hormone used in cattle production, on the structure and function of microbial communities in a fresh water sediment from a lake in Southern Germany were studied in a microcosm experiment. The microbial community structure and the total gene pool of the sediment, assessed by 16S rRNA/rDNA and RAPD fingerprint analysis, respectively, were not significantly affected by TBOH. In contrast, the N-acetyl-glucosaminidase activity was almost 50% lower in TBOH treated samples (P<0.05). Also, the substrate utilization potential, measured using the BIOLOG system, was reduced after TBOH treatment. Interestingly, this potential did not recover at the end of the experiment, i.e. 19 days after the addition of the chemical. Repeated application of TBOH did not lead to an additional reduction in the substrate utilization potential. Overall results indicate that microbial community function was more sensitive to TBOH treatment than the community structure and the total gene pool.

Biodegradation, Environmental↗
PubMed2005

Release of trace metals, sulfate and complexed cyanide from soils contaminated with gas-purifier wastes: a microcosm study.

Deposited gas-purifier wastes are commonly contaminated with trace metals, sulfate and cyanide (CN) compounds. We investigated their release from three soils contaminated with gas-purifier wastes into solution in microcosm experiments under varying redox conditions (E(H) 170-620 mV). The soils differed in pH (2.2; 4.9; 7.4) and featured low amounts of trace metals, but large amounts of total S and total CN. The pH governed trace metal release in the case of the acidic soil and CN release in the case of the slightly alkaline soil. The redox potential controlled trace metal and CN release in the case of the moderately acidic soil. Sources of dissolved SO(4)(2-) were dissolution of gypsum, desorption from Fe oxides and probably oxidation of elemental S. The geochemical behaviors of trace metals (soluble under acidic and reducing conditions) and CN (soluble under alkaline and oxidizing conditions) were diametrically opposed.

Calcium Sulfate↗
PubMed2026

Long-term PFOA and cadmium Co-contamination alters soil carbon, nitrogen, and phosphorus cycling: Insights from metagenomics and metabolomics.

The co-existence of perfluorooctanoic acid (PFOA) and cadmium (Cd) in soil poses a combined threat to microbial communities. However, the ecological effects and underlying mechanisms of their long-term combined exposure remain poorly understood. This study conducted a 90-day soil microcosm experiment to systematically investigate the effects of individual and combined effects of PFOA and Cd on microbial communities. Our results demonstrated that combined pollution of PFOA and Cd significantly affected four soil enzyme activities associated with carbon, nitrogen, and phosphorus cycling. It also influenced microbial thermal activity with an IC50 of PFOA at 0.94&#x202f;mg/kg. The toxic interaction between PFOA and Cd varied with both toxicity indicators and exposure time. At the community level, PFOA and Cd synergistically reduced bacterial diversity and richness, while exerting more complex interactive effects on fungal communities. Metagenomic analysis revealed that PFOA and Cd significantly affected carbon, nitrogen, and phosphorus cycling by inhibiting inorganic phosphorus solubilization genes (gcd, pqqC) and altering key genes in carbon fixation and nitrogen transformation. Metabolomic profiling further demonstrated that PFOA disrupted membrane lipid homeostasis and amino acid metabolism. Meanwhile, the co-existence of Cd exacerbated disturbances in sugar and carbon metabolism. Our findings provide genetic-level insights into microbial responses to long-term PFOA and Cd co-contamination. These results are essential for risk assessment at such co-contamination sites.

Cadmium↗
PubMed2004

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) by Cladosporium sphaerospermum isolated from an aged PAH contaminated soil.

The ability of a Deuteromycete fungus, Cladosporium sphaerospermum, previously isolated from soil of an aged gas manufacturing plant, to degrade polycyclic aromatic hydrocarbons was investigated. This strain was able to degrade PAHs in non-sterile soils (average 23%), including high molecular weight PAHs, after 4 weeks of incubation. In a microcosm experiment, PAH depletion was clearly correlated to fungal establishment. In liquid culture, this strain degraded rapidly benzo(a)pyrene during its early exponential phase of growth (18% after 4 days of incubation). Among extracellular ligninolytic enzyme activities tested, only laccase activity was detected in liquid culture in the absence or in presence of benzo(a)pyrene. C. sphaerospermum might be a potential candidate for an effective bioremediation of aged PAH-contaminated soils.

Biodegradation, Environmental↗
PubMed2005

Factors affecting the biodegradation of PCP by Pseudomonas mendocina NSYSU.

A pentachlorophenol (PCP) degrading bacterium was isolated from PCP-contaminated soils and identified as Pseudomonas mendocina NSYSU (P. mendocina NSYSU). The main objectives of this study were to (1) clarify the factors affecting the ability and efficiency of PCP biodegradation by P. mendocina NSYSU, and (2) optimize the use of this bacterium in bioremediation of PCP. Microcosm experiments were conducted to fulfill the objectives. In batch cultures, P. mendocina NSYSU used PCP as its sole source of carbon and energy and was capable of completely degrading this compound. This was confirmed by the stoichiometric release of chloride ion. Moreover, P. mendocina NSYSU was able to mineralize a high concentration of PCP (150 mg/L). Results from the oxygen concentration experiment reveal that the growth of P. mendocina NSYSU was inhibited under low oxygen and anaerobic conditions. Results indicate that the optimal growth conditions for P. mendocina NSYSU include the following: slightly acidic (6<pH<7), aerobic, and relatively moderate ambient temperature (20 degrees C<temperature<30 degrees C) conditions. Addition of extra carbon sources (sodium acetate and glucose) could not enhance the PCP biodegradation. No PCP byproducts were detected after eight days of incubation in this study. This suggests that P. mendocina NSYSU is able to effectively biodegrade PCP and its biodegradation byproducts without the accumulation of inhibitory toxic compounds. Results from this study could be used to assist the optimization of its use in bioremediation of PCP.

Biodegradation, Environmental↗
PubMed2005

Microbial responses using denaturing gradient gel electrophoresis to oil and chemical dispersant in enclosed ecosystems.

Microbial responses to the addition of oil with or without a chemical dispersant were examined in mesocosm and microcosm experiments by using denaturing gradient gel electrophoresis of bacterial ribosomal DNA and direct cell counting. When a water-soluble fraction of oil was added to seawater, increases in cell density were observed in the first 24h, followed by a decrease in abundance and a change in bacterial species composition. After addition of an oil-dispersant mixture, increases in cell density and changes in community structure coincided, and the amount of bacteria remained high. These phenomena also occurred in response to addition of only dispersant. Our results suggest that the chemical dispersant may be used as a nutrient source by some bacterial groups and may directly or indirectly prevent the growth of other bacterial groups.

Bacteria↗
PubMed2005

Influence of acid volatile sulfides and simultaneously extracted metals on the bioavailability and toxicity of a mixture of sediment-associated Cd, Ni, and Zn to polychaetes Neanthes arenaceodentata.

Laboratory microcosm experiments were conducted to investigate the influence of acid volatile sulfides (AVS) and simultaneously extracted metals (SEM) in sediments on the bioavailability and toxicity of Cd, Ni, and Zn in sediments to polychaete worms Neanthes arenaceodentata. Cohorts of juvenile N. arenaceodentata were exposed to sediments spiked with metal mixtures containing Cd, Ni, and Zn (0.5-15 micromol x g(-1) of total SEM) with Low- (approximately 1 micromol x g(-1)), Medium- (approximately 5 micromol x g(-1)), and High-AVS concentrations (approximately 10 micromol x g(-1)) for 20 days to determine mortality, growth rate, and metal bioaccumulation. Tissue Cd and Zn concentrations at the end of the exposure were significantly higher in sediments with the low-AVS concentration at a given SEM concentration due to the increased dissolved metal concentrations in overlying water (OW). However, tissue Ni concentrations were not related to dissolved Ni in the OW. AVS concentrations also influenced the toxicity of metals to the worms. Significant mortality was observed only at the highest SEM treatments at Low-AVS series. Most individuals survived at the highest SEM treatments at Medium- and High-AVS series. Similarly, the growth rates of worms were reduced in treatments having higher molar differences between SEM and AVS ([SEM-AVS]). Overall, the bioavailability and toxicity of metals in sediments was not well predicted by sediment metal concentrations only, but considering the influence of geochemical factors (AVS) on the metal bioavailability improved the prediction of toxicity. Also, the relationship between tissue metal concentration and toxicity was used to determine which contaminant was most responsible for the observed toxicity of the metal mixture.

Animals↗
PubMed2004

Bench-scale and field-scale evaluation of catechol 2,3-dioxygenase specific primers for monitoring BTX bioremediation.

The objective of this work was to test a molecular genetic method for in situ monitoring of aerobic benzene, toluene, and xylene (BTX) biodegrading microorganisms. Catechol 2,3-dioxygenase (C23DO) genes occur in bacteria that biodegrade benzene, toluene, xylenes, phenol, biphenyl, and naphthalene. A competitive quantitative polymerase chain reaction (QC-PCR) technique using a single set of primers specific for an entire subfamily of C23DO genes was recently developed. To determine whether bacteria containing these C23DO genes actually exist in environments contaminated by BTX, aerobic microcosms containing previously uncontaminated soil were amended with different aromatic hydrocarbons and DNA extracts were analyzed by QC-PCR for C23DO genes. Anaerobic microcosms were established to confirm that oxygen was also necessary for the enrichment of C23DO genes. Field testing was done at two sites undergoing monitored natural attenuation. In microcosm experiments naphthalene, m-xylene, and p-xylene strongly enriched for C23DO genes while benzene, toluene, and o-xylene produced only transient, weakly detectable genes. In the field study, C23DO genes were detected in groundwater samples contaminated with either xylenes or naphthalene. The results of this study demonstrated that molecular genetic techniques can provide an accurate and rapid method to detect microorganisms capable of aromatic hydrocarbon biodegradation. Such a technique would be useful for monitoring the effectiveness of aeration technologies and for documenting microbial processes for monitored natural attenuation.

Benzene↗
PubMed2004

Decay of intestinal enterococci concentrations in high-energy estuarine and coastal waters: towards real-time T90 values for modelling faecal indicators in recreational waters.

Intestinal enterococci are the principal 'health-evidence-based' parameter recommended by WHO for the assessment of marine recreational water compliance. Understanding the survival characteristics of these organisms in nearshore waters is central to public health protection using robust modelling to effect real-time prediction of water quality at recreation sites as recently suggested by WHO and the Commission of the European Communities Previous models have more often focused on the coliform parameters and assumed two static day-time and night-time T90 values to characterise the decay process. The principal driver for enterococci survival is the received dose of irradiance from sunlight. In the water column, transmission of irradiance is determined by turbidity produced by suspended material. This paper reports the results of irradiated microcosm experiments using simulated sunlight to investigate the decay of intestinal enterococci in relatively turbid estuarine and coastal waters collected from the Severn Estuary and Bristol Channel, UK. High-turbidity estuarine waters produced a T90 value of 39.5 h. Low-turbidity coastal waters produced a much shorter T90 value of 6.6 h. In experiments receiving no irradiation, high-turbidity estuarine waters also produced a longer T90 of 65.1 h compared with corresponding low-turbidity coastal waters, T90 24.8 h. Irradiated T90 values were correlated with salinity, turbidity and suspended solids (r>0.8, p<0.001). The results suggest that enterococci decay in irradiated experiments with turbidity >200 NTU is similar to decay observed under dark conditions. Most significantly, these results suggest that modelling turbidity and or suspended solids offers a potential means of predicting T90 values in 'real-time' for discrete cells of a hydrodynamic model.

Dose-Response Relationship, Radiation↗
PubMed2026

Novel bacterial hosts and mobile genetic structure of tet(X) variants in tetracycline-contaminated aquatic environment uncovered by culture and long-read metagenomics.

Clinically important tigecycline (3rd-generation tetracycline) resistance tet(X) variants were inferred to have evolutionarily originated from environmental bacteria, and have been recognized among environment, human and animals. However, genetic basis for environmental proliferation and dissemination of tet(X) variants remains ambiguous. This study profiled tet(X) variants at gene, contig, isolate, and community levels in environmental community subjected to long-term stepwise increasing oxytetracycline (1st-generation tetracycline) or tigecycline pressure using long-term microcosm experiments, quantitative PCR, bacterial isolation, whole-genome sequencing, and Nanopore-based long-read metagenomics. We confirmed that both oxytetracycline and tigecycline enriched the abundance of tetracycline resistance genes especially oxytetracycline-enriched tet(X3). Unexpectedly diverse bacterial hosts and genetic structure of tet(X)-positive mobile elements in the environment microbiome were identified using bacterial isolation and long-read Nanopore metagenomics. Pseudomonas defluvii was first reported to carry tet(X3) in the chromosome, forming IS26-tet(X3)-res-ISCR2 circular intermediate to transfer between different DNA molecules. Database mining revealed similar mobile segments have prevailed among animal-derived Acinetobacter species. Unlike the widely reported ISCR2-mediated transfer of tet(X6), we identified a novel mobile multidrug transposon TnAs3 where tet(X6) and class 1 integron co-transferred as its passenger region. Mobile tet(X2)-ere(D)-aadS-erm(F)-blaOXA-347 segment was annotated in Runella, and co-occurrences of tet(X2) and ere(D), aadS, blaOXA-347 were also found in Flavobacterium, Arsenicibacter, Chryseobacterium and Pedobacter. Overall, tetracycline-contaminated aquatic microbiome harboured diverse mobile tet(X)-positive segments which have not yet been acquired by clinical pathogens, and thus served as the genetic pool of tet(X) variants together with indigenous bacterial hosts, especially the newly reported Pseudomonas defluvii. Reducing pollution of older-generation tetracyclines would be a proactive way to mitigate environmental evolution and possible clinical effects of tet(X) variants.

Metagenomics↗
PubMed2003

HCH distribution and microbial parameters after liming of a heavily contaminated soil in Rio de Janeiro.

The closing down of a lindane factory near Rio de Janeiro, over 45 years ago, left an area heavily contaminated with hexachlorocyclohexane (HCH). Remediation by soil liming was applied by government authorities in 1995. This study aims to evaluate the HCH distribution and impact on soil microbiota due to contamination and liming. Microcosm experiments with uncontaminated soil mixed with HCH and lime indicated that lime-promoted dechlorination of HCH molecules led to leaching and volatilization of metabolites. The treatment applied transformed but did not solve the problem as most of the HCH remains in the soil. Reduced microbial respiratory activity was measured in contaminated field samples. Higher respiration rates in uncontaminated soil were reduced by HCH and lime addition; the sole addition of HCH caused a temporary increase in soil respiration, and stimulation occurred with oxygen and/or nutrient addition. A heterotrophic bacterial population around 10(9)CFU/g was found in polluted field soil, some well-known degraders having been isolated. Native soil microbiota showed resistance to high amounts of HCH and alkaline pH. The results allow considering bioremediation rather than chemical treatments to clean up the area.

Bacteria↗
PubMed2001

Seawater-atmosphere O(2) exchange rates in open-top laboratory microcosms: application for continuous estimates of planktonic primary production and respiration.

Seawater-atmosphere O(2) exchange rates were experimentally measured in open-top laboratory microcosms. The objective was to establish the relationships between turbulence and oxygen transfer velocity, and thus correct continuously measured day-night changes in dissolved oxygen as estimates of planktonic primary production and respiration. After saturating 15-l sterile seawater microcosms with an oxygen-poor gas mix (4.9% O(2), 95.1% N(2)), the microcosms were left to equilibrate with the atmosphere under different turbulence conditions. The rate of increase in dissolved O(2) was measured at 15-min intervals with polarographic-pulsed electrodes and the corresponding values of the oxygen transfer velocity (the K(O(2)) constant for the different turbulence conditions) were determined. After pooling these and literature data obtained in similar experimental conditions, the relation between epsilon (turbulent kinetic energy dissipation rates) and K(O(2)) was determined. Theoretical K(O(2)) values were also calculated using semi-empirical models in which oxygen transfer velocity (K(O(2))) is related to wind velocity. Theoretical, wind related K(O(2)) values were significantly higher than the experimental ones, and as a consequence overestimate primary production and underestimate respiration rates, even resulting in nocturnal O(2) increase. The magnitude of the differences between experimentally derived and theoretically calculated oxygen transfer velocity, precludes the use of wind-derived equations to calculate K(O(2)) in meso- and microcosms experiments not affected by wind, while the equation obtained relating experimental epsilon and K(O(2)) provides statistically reliable estimations of primary production and respiration.

Journal Article↗
PubMed2002

Impact of elevated ammonium on reproduction in two Hawaiian scleractinian corals with different life history patterns.

Elevated nutrients have the potential to disrupt reproduction in scleractinian corals, with consequent impacts on population dynamics. Reproduction in broadcast spawning (Montipora capitata) and brooding (Pocillopora damicornis) species was assessed following exposure to elevated ammonium in a microcosm experiment. Planulation in P. damicornis ceased following 4 months of ammonium exposure and did not recover until 3 months after termination of nutrient enrichment. Larval settlement and survivorship were not affected by ammonium enrichment. Few significant changes were found for reproductive parameters of M. capitata. There was a significant but small decrease in egg size (430 microm in control eggs to 408 microm in eggs from ammonium enrichment treatments), but no differences in total fecundity or fertilization success. This may be related to the presence of zooxanthellae in the eggs of M. capitata, in contrast to changes in reproduction previously reported in Acropora species, whose eggs do not contain zooxanthellae.

Animals↗