Development of q-PCR approaches to assess water quality: effects of cadmium on gene expression of the diatom Eolimna minima

This study was undertaken to develop molecular tools to assess water quality using diatoms as the biological model. Molecular approaches were designed following the development of a rapid and easy RNA extraction method suited to diatoms and the sequencing of genes involved in mitochondrial and photosystem metabolism. Secondly the impact of cadmium was evaluated at the genetic level by q-PCR on 9 genes of interest after exposure of Eolimna minima diatom populations cultured in suspension under controlled laboratory conditions. Their growth kinetics and Cd bioaccumulation were followed.Population growth rates revealed the high impact of Cd at 100 μg/L with total inhibition of growth. These results are linked to the high bioaccumulation values calculated after 14 days of exposure, 57.0 ± 6.3 μg Cd/g dw and 734.1 ± 70 μg Cd/g dw for exposures of 10 and 100 μg Cd/L respectively.Genetic responses revealed the impact of Cd on the mitochondrial metabolism and the chloroplast photosystem of E. minima exposed to 10 and 100 μg Cd/L with induction of cox1, 12S, d1 and psaA after 7 days of exposure for the concentration of 100 μg Cd/L and of nad5, d1 and psaA after 14 days of exposure for both conditions.This is the first reported use of q-PCR for the assessment of toxic pollution on benthic river diatoms. The results obtained presage interesting perspectives, but the techniques developed need to be optimized before the design of new water quality diagnosis tools for use on natural biofilms.     

Effect of chromium on the level of IL-12 and IFN-gamma in occupationally exposed workers

Chromium may affect humoral and cellular immunity, acting on T lymphocytes as well as on granulocytes and monocytes cells. Cytokines play an important role in the immune balance. In this study, the level of IL-12 and IFN-γ were evaluated in the sera and PHA/LPS stimulated culture supernatant of human PBMCs of healthy volunteers and occupationally exposed chromium workers. All the workers were highly exposed to chromium having mean of 104.65 ± 77.21 µg/dL (range 23.7-316.8 µg/dL). A suspension of exposed and unexposed human PBMC (0.5 × 10⁶ cells/ml) prepared and cultured in RPMI-1640 supplemented with 10% FCS for 18 h in the presence or absence of LPS (10 ng/ml) which used for stimulation of IL-12 and IFN-γ. The level of IL-12 and IFN-γ were evaluated in the sera samples as well as LPS stimulated and unstimulated culture supernatant of h-PBMCs of chromium exposed workers. In these chromium exposed workers the level of IL-12 was 433.66 ± 197.49 pg/ml and 983.45 ± 330.99 pg/ml in LPS stimulated culture supernatant of normal individuals and highly chromium exposed workers, which was significant (P < 0.05). Although the level of IL-12 was (78.61 ± 61.03 pg/ml to 146.52 ± 46.37 pg/ml) elevated in unstimulated culture supernatant of h-PBMCs of chromium exposed individuals as compared to control, but it was not significant. This observation also suggests that a significant increase in IFN-γ production in LPS stimulated and unstimulated culture supernatant of h-PBMCs of chromium exposed workers as compared to control. However, IFN-γ level have a significant positive correlation between blood chromium level (r = 0.833, t = 6.3872, P 0.05) and exposure time (in years) (r = 0.8916, t = 8.3540, P 0.05) of the occupationally exposed workers.     

Factors controlling Hg levels in two predatory fish species in the Negro river basin, Brazilian Amazon

A number of environmental factors have been shown to influence the dynamics of Hg in aquatic ecosystems. Here we investigate the influence of fish size, pH, dissolved organic carbon (DOC), and the availability of potential methylation sites (floodplain forests and hydromorphic soils) on the concentration of total Hg in two carnivorous fishes: Cichla spp. and Hoplias malabaricus in the Negro River, Brazil. Fish and water samples for chemical analysis were collected from 33 sites in the Negro basin. The percentage of alluvial floodplains and hydromorphic soils (potential methylation sites) in the drainage basin upstream from each sampling point was estimated from radar imagery and existing soil maps with GIS. The average of Hg concentrations were 0.337 ppm (SD = 0.244) in Cichla spp. and 0.350 ppm (SD = 0.250) in H. malabaricus. Although the study area was geographically isolated from most major anthropogenic Hg sources, over 18% of Cichla spp. and 29% of H. malabaricus had Hg concentrations above 0.5 ppm, indicating naturally high background levels of Hg. Hg concentrations increased with size in both Cichla spp. (r² = 0.664, p = 0.000) and H. malabaricus (r² = 0.299, p = 0.000). Hg concentrations in H. malabaricus also increased with percent floodable area (p = 0.006), pH (p = 0.000) and DOC (0,063). In Cichla spp, Hg increased only in relation to percent floodable area (p = 0.000). Hydromorphic soils did not influence fish Hg.     

Disinfection of Legionella pneumophila by ultrasonic treatment with TiO2

An ultrasonic treatment system, using a TiO₂ photocatalyst, was used to disinfect Legionella pneumophila. A kinetic study of the process indicates that TiO₂ significantly improves the disinfection process. The concentrations of viable cells were reduced to 6% of the initial concentrations in the presence of 0.2 g/ml TiO₂ after a 30 min of treatment period, while only an 18% reduction was observed in the absence of TiO₂. The potency of the disinfection could be enhanced, to some extent, by increasing the amount of TiO₂ used. Cell concentrations were decreased by an order of 3 within 30 min of treatment in the presence of 1.0 g/ml TiO₂. The disinfection power in the presence of TiO₂ versus Al₂O₃ was also compared and the findings showed that TiO₂ induced a higher cell killing. No significant effect of initial cell concentration on the disinfection was found in the range of 10²-10⁷ CFU/ml after a 30 min of treatment period. The mechanism of cell killing was investigated by examining the effects of OH radical scavengers such as ascorbic acid, histidine and glutathione. The disinfection power was reduced in samples that contained these radical scavengers, thus indicating the importance of OH radicals.     

Effect of cadmium, lead and arsenic on the oviposition, hatching and embryonic survival of Biomphalaria glabrata

Biomphalaria glabrata is a widespread freshwater gastropod mollusc. The easy aquaculture of these organisms allow its use as an accessible tool for contamination bioassays. B. glabrata showed marked metabolic responses when exposed to cadmium, lead and arsenic. Those responses could also affect the reproduction of the snails. Taking into account this hypothesis, B. glabrata were exposed for 96 h (acute laboratory bioassays) to different concentrations of cadmium (0.1, 0.05 and 0 mg/L), lead (0.5, 0.1, 0.05 and 0 mg/L) and arsenic (0.5, 0.1, 0.05 and 0 mg/L). Snails were removed from the aquaria while eggs were left in the same contaminant concentrations. The effect of the assayed toxicants on snail reproduction was registered as the alterations of the total number of laid eggs (TNLE), hatching time and embryonic survival.At 0.10 mg/L cadmium significantly decreased the TNLE (p < 0.05) and no embryos survived. The lowest assayed level (0.05 mg/L) of cadmium, delayed the hatching time twice when it was compared with the control group (p < 0.01).Lead decreased the TNLE at 0.5 mg/L level (p < 0.01). The other assayed doses (0.05 and 0.10 mg/L) also decreased embryonic survival significantly (p < 0.05 and p < 0.01 respectively) and extended twice the time to hatching (p < 0.01). The 0.50 mg/L level killed all embryos.Arsenic at all studied concentrations decreased the TNLE (p < 0.05) while the hatching time was increased by 50%. Embryo survival only decreased at the highest level (0.5 mg/L) of arsenic assayed.In summary, the acute exposure (96 h) to cadmium lead and arsenic, altered the reproduction of B. glabrata, modifying the TNLE, hatching time and embryonic survival.     

In vitro evaluation of cytotoxicity of engineered carbon nanotubes in selected human cell lines

In this study, we used a systematic approach to study and compare the in vitro cytotoxicity of selected engineered carbon nanotubes (CNTs) to test cell lines including human skin keratinocytes, lung cells and lymphocytes. Results of fluorescein diacetate (FDA) uptake in T4 lymphocyte A3 cells indicated cytotoxicity caused by single-walled carbon nanotubes (SWCNTs) at concentrations of 2, 5 and 10 ppm. At 2 ppm, the SWCNT treatment group retained 71.3% viability compared to the PBS control group. At 10 ppm, cellular viability further decreased to 56.5% of the PBS control group. In the skin keratinocyte HaCaT cells and lung MSTO-211H cells, the SWCNT did not demonstrate any cytotoxicity at concentrations of 2 and 5 ppm but slightly inhibited HaCaT cells and caused significant toxicity to MSTO-211H cells at 10 ppm. Multi-walled carbon nanotube (MWCNT) testing showed significant cytotoxicity to A3 cells in a dose-dependent manner. At 10 ppm the viability of the cells decreased to 89.1% compared to the PBS control. In MSTO-211H cells, MWCNT caused significant toxicity at concentrations of 2 ppm and higher. By comparison, HaCaT cells were inhibited significantly only at 10 ppm. Overall, the test CNTs inhibited cellular viabilities in a concentration, cell type, and CNT type-dependent pattern. The viabilities of the MWCNT-impacted cells are higher than the corresponding SWCNT groups. We speculate that on a per volume basis, the greater availability of defects and contaminants for cellular interaction may contribute to the higher cytotoxicity of SWCNT in this study. The interaction between the SWCNTs and A3 lymphocytes was also observed by scanning electron microscopy. The mechanism for causing cell death in this study was attributed to apoptosis and necrosis after physical penetration by CNTs and oxidative stress via formation of reactive oxygen species.     

Rhizosphere acidification of faba bean, soybean and maize

Interspecific facilitation on phosphorus uptake was observed in faba bean/maize intercropping systems in previous studies. The mechanism behind this, however, remained unknown. Under nitrate supply, the difference in rhizosphere acidification potential was studied by directly measuring pH of the solution and by visualizing and quantifying proton efflux of roots between faba bean (Vicia faba L. cv. Lincan No.5), soybean (Glycine max L. cv. Zhonghuang No. 17) and maize (Zea mays L. cv. Zhongdan No.2) in monoculture and intercrop, supplied without or with 0.2 mmol L^− 1 P as KH₂PO₄. The pH of the nutrient solution grown faba bean was lower than initial pH of 6.0 from day 1 to day 22 under P deficiency, whereas the pH of the solution with maize was declined from day 13 after treatment. Growing soybean increased solution pH irrespective of P supply. Under P deficiency, the proton efflux of faba bean both total (315.25 nmol h^− 1 plant^− 1) and specific proton efflux (0.47 nmol h^− 1 cm^− 1) was greater than that those of soybean (21.80 nmol h^− 1 plant^− 1 and 0.05 nmol h^− 1 cm^− 1, respectively). Faba bean had much more ability of rhizosphere acidification than soybean and maize. The result can explain partly why faba bean utilizes sparingly soluble P more effectively than soybean and maize do, and has an important implication in understanding the mechanism behind interspecific facilitation on P uptake by intercropped species.     

Dietary high protein and vitamin C mitigates endosulfan toxicity in the spotted murrel, Channa punctatus (Bloch, 1793)

The amelioration effect of dietary high protein and vitamin C against stress was evaluated in spotted murrel, Channa punctatus, exposed to endosulfan. Two hundred and forty fish (average weight: 27.01 g/fish), distributed equally into 4 different groups (control, T₁, T₂, and T₃), each with 6 replicates were fed with control (40% crude protein, CP and 0.1% vitamin C), T₁ (40% CP and 0.1% vitamin C), T₂ (50% CP and 0.1% vitamin C), and T₃ (50% CP and 0.2% vitamin C) diets for 90 days. Groups fed T₁, T₂, and T₃ diets were exposed to sublethal endosulfan concentration, whereas the control was maintained without endosulfan exposure. Results indicated significant reduction in the growth performance, survival, and activities of lactate dehydrogenase (liver and muscle), malate dehydrogenase (liver and muscle), enzymes of protein metabolism (aspartate amino transferase in liver and alanine amino transferase in liver and muscle), acetyl choline esterase (brain), alkaline phosphatase activity (liver), and ATPase (gill) enzymes of group fed control diet and exposed to endosulfan. However, endosulfan exposed fish fed high CP and vitamin C diet exhibited significant (P < 0.05) improvement in their growth performance and metabolic enzyme activities. Further, high CP and vitamin C diet reduced endosulfan accumulation in the muscle. Overall results indicate that vitamin C (0.2%) supplementation in high CP (50%) diet improves growth, metabolism, and reduce endosulfan bioaccumulation in C. punctatus.     

Biochemical stress response in tetradifon exposed Daphnia magna and its relationship to individual growth and reproduction

Environmental risk assessment of chemicals toxicity requires the use of costly and labor-intensive chronic data and short-term tests provide additional information. Energy budget is used by the animals for their growth, reproduction, and metabolism and it is reduced in case of toxic stress. Tetradifon acaricide is frequently used in the European Mediterranean region and it is implicated in aquatic environmental pollution. Previous studies showed that the EC₅₀-24 h of tetradifon on Daphnia magna was 8.92 mg/L. Based on that, D. magna were exposed to sublethal tetradifon concentrations of 0.10, 0.18, 0.22 and 0.44 mg/L for five days in order to investigate their effect on intermediate metabolism. Caloric content was determined as biomarker of tetradifon toxicity. Results were analyzed using one-way analysis of variance (ANOVA) and Duncan's significant difference test was used to find differences between groups (α was set at p = 0.05). Daphnids energy content decreased as tetradifon concentration increased. At 120-h caloric content was depleted > 51% at pesticide concentrations of 0.18 mg/L and higher. In order to determine a possible link between the 5-d test and the 21-d chronic test, animals under short-term test were exposed to the same pesticide concentrations known to cause adverse effects on reproduction, growth and survival. Results from the present study indicated a good correlation between the proposed 5-day test and daphnid energy budget. Comparison between both, caloric content results and the chronic effect values obtained using life-table studies, suggested a good fit between them. These studies can be used as earlier, predictive and useful tests with comparable results to the classic chronic ones. Our results indicate that caution must be done about the use of tetradifon in the aquatic environment.     

Degradation of diclofenac by TiO2 photocatalysis: UV absorbance kinetics and process evaluation through a set of toxicity bioassays

In the present study the degradation kinetics and mineralization of diclofenac (DCF) by the TiO₂ photocatalysis were investigated in terms of UV absorbance and COD measurements for a wide range of initial DCF concentrations (5-80 mg L⁻¹) and photocatalyst loadings (0.2-1.6 g TiO₂ L⁻¹) in a batch reactor system. A set of bioassays (Daphnia magna, Pseudokirchneriella subcapitata and Artemia salina) was performed to evaluate the potential detoxification of DCF. A pseudo-first-order kinetic model was found to fit well most of the experimental data, while at high initial DCF concentrations (40 and 80 mg L⁻¹) and at 1.6 g TiO₂ L⁻¹ photocatalyst loading a second-order kinetic model was found to fit the data better. The toxicity of the treated DCF samples on D. magna and P. subcapitata varied during the oxidation, probably due to the formation of some intermediate products more toxic than DCF. Unicellular freshwater algae was found to be very sensitive to the treated samples as well as the results from D. magna test were consistent to those of algae tests. A. salina was not found to be sensitive under the investigated conditions. Finally, UV absorbance analysis were found to be an useful tool for a fast and easy to perform measurement to get preliminary information on the organic intermediates that are formed during oxidation and also on their disappearance rate.     

A method to measure total antioxidant capacity against peroxyl radicals in aquatic organisms: Application to evaluate microcystins toxicity

Determination of total antioxidant capacity, instead of the measurements of limited number of antioxidants, is very important for the understanding of how antioxidants interact with reactive oxygen species (ROS). Several techniques already exist with this propose, although some of them are extremely time-consuming. A new methodology is proposed, based on the detection of ROS by fluorometry (ex/em: 485/520 nm) employing 2′,7′-dichlorofluorescein diacetate (H₂DCF-DA) as substrate. Supernatant of homogenized samples from different organs (gill, muscle, liver, and brain) of the teleost fish Jenynsia multidentata (Anaplebidae) were exposed to peroxyl radicals generated by thermal (35 °C) decomposition of 2,2′-azobis (2 methylpropionamidine) dihydrochloride (ABAP, 4 mM). Different protein concentrations (0.5, 1, 2 and 8 mg/ml) were assayed to get the best signal and curve fitting of fluorescence data over time (30 min). Total antioxidant capacity against peroxyl radicals was estimated as the difference in ROS area with and without ABAP, relative to the fluorescence registered without ABAP. For application of this methodology, J. multidentata specimens were exposed for 24 h to microcystins, cyanotoxins known to induce oxidative stress. Almost all organs showed a lower antioxidant capacity (p < 0.05) in samples with 8 mg proteins/ml, when compared to protein content of 1-2 mg/ml. In liver samples, higher (p < 0.05) free iron content was determined in samples with 8 mg proteins/ml. Sensitivity test employing GSH spiked in homogenized samples showed the protocol efficiency in detecting total antioxidant capacity. In the test with microcystins a dose-dependent decrease (p < 0.05) of antioxidant competence in gills and brain and an inverse result with liver samples were observed. The use of antioxidant defenses was efficient in avoiding oxidative damage, as the content of oxidized proteins was not altered. Data obtained show the potential of this new methodology to be used in ecotoxicological studies.     

Comparison of toxicity and release rates of Cu and Zn from anti-fouling paints leached in natural and artificial brackish seawater

Biocide-containing anti-fouling paints are regulated and approved according to the added active ingredients, such as Cu. Biocide-free paints are considered to be less environmentally damaging and do not need an approval. Zn, a common ingredient in paints with the potential of causing adverse effects has received only minor attention. Laboratory experiments were conducted in artificial brackish seawater (ASW) and natural brackish seawater (NSW) to quantify release rates of Cu and Zn from biocide-containing and biocide-free labeled eroding anti-fouling paints used on commercial vessels as well as leisure boats. In addition, organisms from three trophic levels, the crustacean Nitocra spinipes, the macroalga Ceramium tenuicorne and the bacteria Vibrio fischeri, were exposed to Cu and Zn to determine the toxicity of these metals. The release rate of Cu in NSW was higher from the paints for professional use (3.2-3.6 µg cm⁻² d^− 1) than from the biocide leaching leisure boat paint (1.1 µg cm⁻² d^− 1). Biocide-free paints did leach considerably more Zn (4.4-8.2 µg cm⁻² d^− 1) than biocide-containing leisure boat paint (3.0 µg cm⁻² d^− 1) and ship paints (0.7-2.0 µg cm⁻² d^− 1). In ASW the release rates of both metals were notably higher than in NSW for most tested paints. The macroalga was the most sensitive species to both Cu (EC₅₀ = 6.4 µg l^− 1) and Zn (EC₅₀ = 25 µg l^− 1) compared to the crustacean (Cu, LC₅₀ = 2000 µg l^− 1 Zn, LC₅₀ = 890 µg l^− 1), and the bacteria (Cu, EC₅₀ = 800 µg l^− 1 and Zn, EC₅₀ = 2000 µg l^− 1). The results suggest that the amounts of Zn and Cu leached from anti-fouling paints may attain toxic concentrations in areas with high boat density. To fully account for potential ecological risk associated with anti-fouling paints, Zn as well as active ingredients should be considered in the regulatory process.     

Oxidative stress responses of Daphnia magna exposed to TiO2 nanoparticles according to size fraction

Size is one of important factors determining titanium dioxide nanoparticle (TiO₂ NP) toxicity since penetration is eased with decreasing particle size and bioavailability is increased. The effect of particle size on oxidative stress against titanium dioxide nanoparticle (TiO₂ NP) exposure to Daphnia magna was investigated with both acute and chronic toxicity tests. Experiments on biochemical responses, repeatedly performed after size fractionation of the NPs using filtration, focused on the activities of four antioxidant enzymes: catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX), and glutathione-S-transferase (GST). In the chronic bioassay, the mortality was significantly increased at TiO₂ NP concentrations of 5 and 10 mg/L; however, no reduction of the reproduction ability was observed. Biochemical measurements showed that TiO₂ NP exposure significantly increased the antioxidant enzyme activities in D. magna. CAT, GPX and GST, but not SOD, showed a concentration-dependent increase. In terms of size fraction, particles ranging from 400 to 800 nm exhibited an increase of antioxidant enzyme activities in GST and GPX. These biochemical level observations suggested that TiO₂ NP toxicity was mediated by reactive oxygen species (ROS) generation via oxidative stress in D. magna. The increased mortality at the concentration of 5 mg/L in the chronic bioassay was attributed to accumulated TiO₂ NPs in the intestine of D. magna, which might induce effects such as oxidative stress relating to the induction of antioxidant enzymes.     

Prevalence and predictors of exposure to multiple metals in preschool children from Montevideo, Uruguay

The extent of children's exposure to multiple toxic metals is not well described in many developing countries. We examined metal exposures in young children (6-37 months) from Montevideo, Uruguay and their mothers (15-47 years) participating in a community-based study. Hair samples collected from 180 children and their mothers were analyzed for: lead (Pb), cadmium (Cd), manganese (Mn), and arsenic (As) concentration using inductively coupled plasma-mass spectrometry (ICP-MS). Median metal levels (μg/g) were: Pb 13.69, Mn 1.45, Cd 0.17, and As 0.09 for children and Pb 4.27, Mn 1.42, Cd 0.08, and As 0.02 for mothers. Of the child and maternal samples, 1.7% and 2.9% were below the limit of detection (LOD) for Cd, and 21.3% and 38.5% were below the LOD for As, respectively. Correlations between maternal and child levels ranged 0.38-0.55 (p < 0.01). Maternal hair metal levels were the strongest predictors of metal concentrations in children's hair. Girls had significantly lower As levels than boys (p < 0.01) but did not differ on other metals. In addition, in bivariate logistic regressions predicting the likelihood that the child would be exposed to multiple metals, hemoglobin < 10.5 g/dL (OR = 2.12, p < 0.05), blood lead (OR = 1.17, p < 0.01), and the mother being exposed to two or more metals (OR = 3.34, p < 0.01) were identified as significant predictors of increased likelihood of multiple metal exposure. Older child age (OR = 0.96, p < 0.05), higher maternal education (OR = 0.35, p < 0.01), and higher number of household possessions (OR = 0.83, p < 0.01) were significantly associated with decreased likelihood of multiple metal exposure. Preschool children in Uruguay are exposed to multiple metals at levels that in other studies have been associated with cognitive and behavioral deficits. Sources of exposure, as well as cognitive and behavioral consequences of multiple metal exposure, should be investigated in this population.     

The influence of biofilms on the migration of uranium in acid mine drainage (AMD) waters

The uranium mine in Königstein (Germany) is currently in the process of being flooded. Huge mass of Ferrovum myxofaciens dominated biofilms are growing in the acid mine drainage (AMD) water as macroscopic streamers and as stalactite-like snottites hanging from the ceiling of the galleries. Microsensor measurements were performed in the AMD water as well as in the biofilms from the drainage channel on-site and in the laboratory. The analytical data of the AMD water was used for the thermodynamic calculation of the predominance fields of the aquatic uranium sulfate (UO₂SO₄) and UO₂⁺⁺ speciation as well as of the solid uranium species Uranophane [Ca(UO₂)₂(SiO₃OH)₂?5H₂O] and Coffinite [U(SiO₄)_1 − x(OH)_4x], which are defined in the stability field of pH > 4.8 and Eh < 960 mV and pH > 0 and Eh < 300 mV, respectively. The plotting of the measured redox potential and pH of the AMD water and the biofilm into the calculated pH-Eh diagram showed that an aqueous uranium(VI) sulfate complex exists under the ambient conditions. According to thermodynamic calculations a retention of uranium from the AMD water by forming solid uranium(VI) or uranium(IV) species will be inhibited until the pH will increase to > 4.8. Even analysis by Energy-filtered Transmission Electron Microscopy (EF-TEM) and electron energy loss spectroscopy (EELS) within the biofilms did not provide any microscopic or spectroscopic evidence for the presence of uranium immobilization. In laboratory experiments the first phase of the flooding process was simulated by increasing the pH of the AMD water. The results of the experiments indicated that the F. myxofaciens dominated biofilms may have a substantial impact on the migration of uranium. The AMD water remained acid although it was permanently neutralized with the consequence that the retention of uranium from the aqueous solution by the formation of solid uranium species will be inhibited.     

Isolation and characterization of a novel pyrene-degrading Bacillus vallismortis strain JY3A

The PAHs-degrading bacterium strain JY3A was newly isolated from the polluted soil in the Jinan Oil Refinery Factory, Shandong Province of China. The isolate was identified as Bacillus vallismortis with respect to its 16S rDNA sequence, DNA-DNA relatedness and fatty acid profiles, as well as various physiological characteristics. The strain was Gram-positive, motile, endospore forming, aerobic, oxidase and catalase-positive. The cells were 0.8-1.0 μm wide and 2.0-2.5 μm long, single or in pairs and sometimes in chains. Bacillus vallismortis strain JY3A could utilize naphthalene, phenanthrene, anthracene, pyrene, fluorene, benzene, toluene, phenol, methanol, ethanol, Tween 80, cyclohexane or catechol as sole carbon source. The strain alone removed 90.5% of pyrene at an initial concentration of 150 ppm in 15 days in the presence of 0.5% (w/w) Tween 80. However, in co-culture with Phanerochaete chrysosporium, JY3A reduced the concentration of pyrene by nearly 55.4% after 7 days of incubation.     

Bacterial responses to Cu-doped TiO2 nanoparticles

The toxicity of Cu-doped TiO₂ nanoparticles (NPs, 20 nm), synthesized by a flame aerosol reactor, to Mycobacterium smegmatis and Shewanella oneidensis MR-1, is the primary focus of this study. Both doped and non-doped TiO₂ NPs (20 nm) tended to agglomerate in the medium solution, and therefore did not penetrate into the cell and damage cellular structures. TiO₂ particles (< 100 mg/L) did not apparently interfere with the growth of the two species in aqueous cultures. Cu-doped TiO₂ NPs (20 mg/L) significantly reduced the M. smegmatis growth rate by three fold, but did not affect S. oneidensis MR-1 growth. The toxicity of Cu-doped TiO₂ NPs was driven by the release of Cu²⁺ from the parent NPs. Compared to equivalent amounts of Cu²⁺, Cu-doped TiO₂ NPs exhibited higher levels of toxicity to M. smegmatis (P-value < 0.1). Addition of EDTA in the culture appeared to significantly decrease the anti-mycobacterium activity of Cu-doped TiO₂ NPs. S. oneidensis MR-1 produced a large amount of extracellular polymeric substances (EPS) under NP stress, especially extracellular protein. Therefore, S. oneidensis MR-1 was able to tolerate a much higher concentration of Cu²⁺ or Cu-doped TiO₂ NPs. S. oneidensis MR-1 also adsorbed NPs on cell surface and enzymatically reduced ionic copper in culture medium with a remediating rate of 61 µg/(liter?OD₆₀₀? hour) during its early exponential growth phase. Since the metal reducing Shewanella species can efficiently “clean” metal-oxide NPs, the activities of such environmentally relevant bacteria may be an important consideration for evaluating the ecological risk of metal-oxide NPs.     

The effects of Aphis fabae infestation on the antioxidant response and heavy metal content in field grown Philadelphus coronarius plants

The purpose of this study was to explore a possible relationship between the soil availability of metals and their concentrations in various parts of Philadelphuscoronarius plants. Moreover, the possible impact of an aphid infestation on the contamination and antioxidant response of plants from the urban environment of Kraków and the reference rural area of Zagaje Stradowskie (southern Poland) was analyzed. The contents of the glutathione, proline, non-protein − SH groups, antioxidants, and phosphorous and the levels of guaiacol peroxidase and catalase activity in leaves and shoots either infested or not by the aphid Aphis fabae Scop., were measured. The potential bioavailability of metals (Cd; Cu; Ni; Pb; Zn) in the soil and their concentrations in P. coronarius plants originating from both sites were compared.The antioxidant responses were generally elevated in the plants in the polluted area. Such reactions were additionally changed by aphid infestation. Generally, the concentrations of metals in the HNO₃ and CaCl₂ extractants of the soils from two layers at the 0-20 and 20-40 cm depths from the polluted area were higher than in those from the reference area. Such differences were found for nickel and lead (in all examined extractants), zinc (in soil extractants from the layer at 20-40 cm) and cadmium (in HNO₃ extractants). Significant positive relationships between the lead concentrations in the soil and in the plants were found. In the parts of plants from the polluted area, higher concentrations of Pb and Zn (leaves and shoots) and Cd (shoots) were recorded. The shoots and leaves of plants infested with aphids had higher concentrations of Zn but lower Pb. Moreover, their leaves had higher contaminations of Cu and Ni. In conclusion, aphids affected not only the antioxidant response of the plants but also their contamination with metals, especially contamination of the leaves.