Protection against UV disinfection of E. coli bacteria and B. subtilis spores ingested by C. elegans nematodes

Nematodes, which occur abundantly in granular media filters of drinking water treatment plants and in distribution systems, can ingest and transport pathogenic bacteria and provide them protection against chemical disinfectants. However, protection against UV disinfection had not been investigated to date.In this study, Caenorhabditis elegans nematodes (wild-type strain N2) were allowed to feed on Escherichia coli OP50 and Bacillus subtilis spores before being exposed to 5 and 40 mJ/cm² UV fluences, using a collimated beam apparatus (LP, 254 nm). Sonication (15 W, 60 s) was used to extract bacteria from nematode guts following UV exposure in order to assess the amount of ingested bacteria that resisted the UV treatment using a standard culture method. Bacteria located inside the gut of C. elegans were shown to benefit from a significant protection against UV. Approximately 15% of the applied UV fluence of 40 mJ/cm² (as typically used in WTP) was found to reach the bacteria located inside nematode guts based on the inactivation of recovered bacteria (2.7 log reduction of E. coli bacteria and 0.7 log reduction of B. subtilis spores at 40 mJ/cm²). To our knowledge, this study is the first demonstration of the protection effect of bacterial internalization by higher organisms against UV treatment, using the specific case of E. coli and B. subtilis spores ingested by C. elegans.     

Assessing the risk posed to free-living soil nematodes by a genetically modified maize expressing the insecticidal Cry3Bb1 protein

Before pest-resistant genetically modified maize can be grown commercially, the risks for soil-beneficial, non-target organisms must be determined. Here, a tiered approach was used to assess the risk to free-living soil nematodes posed by maize genetically modified to express the insecticidal Cry3Bb1 protein (event Mon88017), which confers resistance towards western corn rootworm (Diabrotica virgifera; Coleoptera). The toxicity of purified Cry3Bb1 for the nematode Caenorhabditis elegans was determined using a bioassay and gene expression analysis. In addition, a soil toxicity test was used to assess the effects on C. elegans of rhizosphere soil obtained from plots of an experimental field grown with Mon88017, the near-isogenic cultivar, or either of two conventional cultivars. Finally, the indigenous nematode communities from the experimental field site with Mon88017 and from the control cultivars were analyzed. The results showed a dose-dependent inhibitory effect of Cry3Bb1 on the growth and reproduction of C. elegans, with EC50 values of 22.3 mg l⁻¹ and 7.9 mg l⁻¹, respectively. Moreover, Cry-protein-specific defense genes were found to be up-regulated in the presence of either Cry1Ab or Cry3Bb1. However, C. elegans was not affected by rhizosphere soils from Mon88017 compared to the control plots, due to the very low Cry3Bb1 concentrations, as indicated by quantitative analyses (< 1 ng g⁻¹ soil). Nematode abundance and diversity were essentially the same between the various maize cultivars. At the last sampling date, nematode genus composition in Bt-maize plots differed significantly from that in two of the three non-Bt cultivars, including the near-isogenic maize, but the shift in genus composition did not influence the composition of functional guilds within the nematode communities. In conclusion, the risk to free-living soil nematodes posed by Mon88017 cultivation can be regarded as low, as long as Cry3Bb1 concentrations in soil remain four orders of magnitude below the toxicity threshold.     

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.     

Effect of hybrid UV-thermal energy stimuli on inactivation of S. epidermidis andB. subtilis bacterial bioaerosols

Bioaerosols have become an increasingly important issue due to their harmful effects on human health. As the concern over airborne microorganisms grows, so does the need to develop and study efficient methods of controlling them. In this study, we designed a hybrid system involving ultraviolet (UV) irradiation and thermal energy and investigated its effects on bacterial bioaerosols, followed by a comparison with thermal energy alone and UV irradiation alone. The results show that the hybrid effect caused no variation in the shape of the normalized particle size distributions of S. epidermidis and B. subtilis bioaerosols. However, a physical transport loss of bacterial bioaerosols developed as the temperature inside the glass quartz tube increased. When bacterial bioaerosols were simultaneously exposed to UV irradiation and thermal energy for less than 1.05 s, more than 99% of S. epidermidis bioaerosols were inactivated at 120 °C with exposure to one UV lamp and at 80 °C with exposure to two UV lamps; and 93.5% and 98.5% of B. subtilis bioaerosols were inactivated at 280 °C with exposure to one and two UV lamps, respectively. Moreover, the hybrid UV-thermal stimuli significantly reduced the concentration of ozone, which is a secondary UV-induced pollutant. Our results show that to obtain the same inactivation efficiency, the hybrid UV-thermal stimuli were more efficient than thermal energy alone in terms of energy consumption and produced significantly less ozone than UV irradiation alone. The hybrid stimuli also had higher inactivation efficiency than UV alone. Therefore, these results provide valuable information for the development of new methods for controlling bioaerosols.     

Cross-species extrapolation of chronic nickel Biotic Ligand Models

The use of Biotic Ligand Models (BLMs) to normalize metal ecotoxicity data and predict effects in non-BLM organisms should be supported by quantitative evidence. This study determined the ability of chronic nickel BLMs developed for the cladocera Daphnia magna and Ceriodaphnia dubia to predict chronic nickel toxicity to three invertebrates for which no specific BLMs were developed. Those invertebrates were the snail Lymnaea stagnalis, the insect Chironomus tentans, and the rotifer Brachionus calyciflorus. Similarly, we also determined the ability of chronic nickel BLMs developed for the alga Pseudokirchneriella subcapitata and the terrestrial vascular plant Hordeum vulgare to predict chronic nickel toxicity to the aquatic vascular plant Lemna minor. Chronic nickel toxicity to the three invertebrates and the aquatic plant were measured in five natural waters that varied in pH, Ca, Mg, and dissolved organic carbon (DOC), which are known to affect chronic nickel toxicity and are the important input variables for the chronic nickel BLMs. Nickel toxicity to the three invertebrates varied considerably among the test waters, i.e., a 14-fold variation of EC50s in L. stagnalis, a 3-fold variation in EC20s in C. tentans, and a 10-fold variation in EC20s in B. calyciflorus, but the cladoceran BLMs were able to predict nickel effect concentrations within a factor of two. Nickel toxicity (EC50s) to L. minor varied by 6-fold among the test waters. Although the P. subcapitata and H. vulgare BLMs offered reasonable predictions of nickel EC50s to L. minor, the D. magna and C. dubia BLM showed better predictions. Our results confirm the influence of site-specific pH, hardness, and DOC on chronic nickel toxicity to aquatic organisms, and support the use of chronic nickel BLMs to manage this influence through normalizations of ecotoxicity data.     

Adsorption, sedimentation, and inactivation of E. coli within wastewater treatment wetlands

Bacteria fate and transport within constructed wetlands must be understood if engineered wetlands are to become a reliable form of wastewater treatment. This study investigated the relative importance of microbial treatment mechanisms in constructed wetlands treating both domestic and agricultural wastewater. Escherichia coli (E. coli) inactivation, adsorption, and settling rates were measured in the lab within two types of wastewater (dairy wastewater lagoon effluent and domestic septic tank effluent). In situ E. coli inactivation was also measured within a domestic wastewater treatment wetland and the adsorption of E. coli was also measured within the wetland effluent.Inactivation of E. coli appears to be the most significant contributor to E. coli removal within the wastewaters and wetland environments examined in this study. E. coli survived longer within the dairy wastewater (DW) compared to the domestic wastewater treatment wetland water (WW). First order rate constants for E. coli inactivation within the WW in the lab ranged from 0.09 day⁻¹ (d⁻¹) at 7.6 °C to 0.18 d⁻¹ at 22.8 °C. The average in situ rate constant observed within the domestic wetland ranged from 0.02 d⁻¹ to 0.03 d⁻¹ at an average water temperature of 17 °C. First order rate constants for E. coli inactivation within the DW ranged from 0.01 d⁻¹ at 7.7 °C to 0.04 d⁻¹ at 24.6 °C. Calculated distribution coefficients (K_d) were 19,000 mL g⁻¹, 324,000 mL g⁻¹, and 293 mL g⁻¹ for E. coli with domestic septic tank effluent (STE), treated wetland effluent (WLE), and DW, respectively. Approximately 50%, 20%, and 90% of E. coli were “free floating” or associated with particles <5 μm in size within the STE, WLE, and DW respectively. Although 10-50% of E. coli were found to associate with particles >5 μm within both the STE and DW, settling did not appear to contribute to E. coli removal within sedimentation experiments, indicating that the particles the bacteria were associated with had very small settling velocities.The results of this study highlight the importance of wastewater characterization when designing a treatment wetland system for bacterial removal. This study illustrated the level of variability in E. coli removal processes that can be observed within different wastewater, and wetland environments.     

Evaluation of the acute, chronic and teratogenic effects of a mixture of eleven pharmaceuticals on the cnidarian, Hydra attenuata

Pharmaceuticals have recently emerged as novel pollutants of potential concern in the aquatic environment where they are commonly introduced as complex mixtures via municipal effluent. In the present experiment, the freshwater cnidarian Hydra attenuata was exposed to a mixture of 11 pharmaceuticals (ibuprofen, naproxen, gemfibrozil, bezafibrate, carbamazepine, sulfapyridine, oxytetracycline, novobiocin, trimethoprim, sulfamethoxazole and caffeine) up to 10 000 times (×) the concentration found in municipal effluent. Hydra regeneration and teratogenicity was measured, having an IC₅₀ of 781× and was found to be non teratogenic with an A/D value of ∼ 1. Toxicity was investigated using both lethal (based on morphology) and sub-lethal (based on morphology, feeding behaviour, hydranth number and attachment) endpoints. The pharmaceutical mixture incurred a significant decrease in morphology at 0.1, 10 and 100× but a significant increase at 1000×. All parameters were significantly reduced at 10 000×. An EC₅₀ of 425× and 65× based on morphology and feeding respectively and a toxicity threshold (TT) of 3.2× were calculated. When compared to the toxicity of each pharmaceutical exposed individually as previously reported [Quinn B, Gagné F, Blaise C. An investigation into the acute and chronic toxicity of eleven pharmaceuticals found in wastewater effluent on the cnidarian, H. attenuata. Sci Total Environ 2008a; 389: 306-314], the compounds in the mixture were present at concentrations 2 to 3 orders of magnitude lower for the equivalent toxicity (EC₅₀ and TT). These results indicate that pharmaceuticals act additively in a mixture, having sub-lethal effects at environmentally relevant (µg/L-ng/L) concentrations and that their combined concentrations could potentially prove significantly ecotoxic to Hydra and possibly to other aquatic taxa.     

Effects of Mg and H on the toxicity of Ni to the unicellular green alga Pseudokirchneriella subcapitata: Model development and validation with surface waters

In this study, increasing Mg concentrations and decreasing pH were observed to decrease Ni toxicity to the green alga Pseudokirchneriella subcapitata. To investigate to what extent the original biotic ligand model (BLM) concept could explain Ni toxicity as a function of water chemistry, the protective effects of Mg²⁺ and H⁺ were modeled as BLM-type single-site competition effects. The model parameters representing these effects were log K_MgBL = 3.3 and log K_HBL = 6.5. The BLM was capable of predicting Ni toxicity by an error of less than a factor of 2 in most synthetic and natural waters used in this study. However, since the relationship between 72-h E_rC50_Ni²⁺ (i.e. the 72-h E_rC50 expressed as Ni²⁺ activity) and H⁺ activity was not linear over the entire tested pH range, only the ‘linear part’ between pH 6.45 and 7.92 was used for derivation of log K_HBL. This nonlinearity indicates that the effect of pH can probably not be attributed to H⁺ competition with Ni²⁺ for a single site alone. When modeling the effect of pH as a linear relation between 72-h E_rC50_pNi²⁺? (= − log (72-h E_rC50_Ni²⁺ corrected for the presence of Mg)) and pH, the applicability of the model was successfully extended to pH levels as low as 6.01. This type of empirical model has also been used in our previous studies on the development of a chronic Ni bioavailability model for Daphnia magna and a long-term Ni bioavailability model for rainbow trout. Finally, we could not detect a statistically significant interactive effect of pH and Mg on the toxicity of Ni²⁺ to P. subcapitata and this is in line with the formulation of our empirical model.     

Feeding characteristics of a golden alga (Poterioochromonas sp.) grazing on toxic cyanobacterium Microcystis aeruginosa

Microcystis aeruginosa has quickly risen in infamy as one of the most universal and toxic bloom-forming cyanobacteria. Here we presented a species of golden alga (Poterioochromonas sp. strain ZX1), which can feed on toxic M. aeruginosa without any adverse effects from the cyanotoxins. Using flow cytometry, the ingestion and maximal digestion rates were estimated to be 0.2∼1.2 and 0.2 M. aeruginosa cells (ZX1 cell)⁻¹ h⁻¹, respectively. M. aeruginosa in densities below 10⁷ cells mL⁻¹ could be grazed down by ZX1, but no significant decrease was observed when the initial density was 3.2 × 10⁷ cells mL⁻¹. ZX1 grazing was a little influenced by the light intensity (0.5∼2500 lx) and initial pH of the medium (pH = 5.0∼9.5). ZX1 could not survive in continuous darkness for longer than 10 days. The pH value was adjusted to 8 by ZX1 while to 10 by M. aeruginosa. This study may shed light on understanding the ecological interactions between M. aeruginosa and mixotrophic Poterioochromonas sp. in aquatic ecosystems.     

The impact of barley straw conditioning on the inhibition of Scenedesmus using chemostats

The current paper investigates the role of barley straw conditioning on inhibiting the alga Scenedesmus. Fresh, pre-rotted and white rot fungi (WRF) augmented straw was tested in a series of chemostat experiments over 15 weeks. All three systems were effective at inhibiting the alga with differences observed in the lag time before inhibition occurred and the rate of alga decline. Lag times of 8, 4 and 1 week(s) were recorded for the fresh, rotted and fungi-treated straws, respectively, with a maximum inhibition rate of >7 × 10⁴ cells week⁻¹ observed for the fungi pre-treated system. Overall, the results indicate that pre-treatment is a viable method to enable barley straw to be used in a more reactive manner. Explanation is postulated that during pre-treatment no alternative sources of nitrogen are available, thereby leading to greater bacterial decomposition of straw lignin to release inhibitory substances. The principle of utilising an engineered pre-treatment by inoculating barley straw with WRF to enhance the impact of the straw on algal inhibition has been clearly demonstrated. Further work is required to understand how the straw pre-treatment stage can be reduced to minimise its duration while maximising the inhibitory effect of adding barley straw.     

Sublethal toxicity and biotransformation of pyrene in Lumbriculus variegatus (Oligochaeta)

The aim of this work was to study the toxicity and biotransformation of polyaromatic hydrocarbon (PAH) pyrene in the oligochaete aquatic worm, Lumbriculus variegatus. PAHs are ubiquitous environmental pollutants that pose a hazard to aquatic organisms, and metabolizing capability is poorly known in the case of many invertebrate species. To study the toxicity and biotransformation of pyrene, the worm was exposed for 15 days to various concentrations of water-borne pyrene. The dorsal blood vessel pulse rate was used as a sublethal endpoint. Pyrene biotransformation by L. variegatus was studied and the critical body residues (CBR) were estimated for pyrene toxicity. The toxicokinetics of pyrene uptake was evaluated. A combination of radiolabeled (¹⁴C) and nonlabeled pyrene was used in the exposures, and liquid scintillation counting (LSC) and high-pressure liquid chromatography were employed in both water and tissue residue analyses. The results showed that L. variegatus was moderately able to metabolize pyrene to 1-hydroxypyrene (1-HP), thus demonstrating that the phase-I-like oxidizing enzyme system metabolizes pyrene in L. variegatus. The amount of the 1-HP was 1-2% of the amount of pyrene in the worm tissues. The exposure to pyrene reduced the blood vessel pulse rate significantly (p < 0.05), showing that pyrene had a narcotic effect. The estimated CBRs remained constant during the exposure time, varying from 0.120 to 0.174 mmol pyrene/kg worm wet weight. The bioconcentration factors (BCF) decreased as exposure concentration increased. It was suggested that the increased toxicity of pyrene accounted for the decrease in BCFs by lowering the activity of the organism.     

Survey of pathogenic free-living amoebae and Legionella spp. in mud spring recreation area

Acanthamoeba, Hartmannella, and Naegleria are free-living amoebae, ubiquitous in aquatic environments. Several species within these genera are recognized as potential human pathogens. These free-living amoebae may facilitate the proliferation of their parasitical bacteria, such as Legionella. In this study, we identified Acanthamoeba, Hartmannella, Naegleria, and Legionella using various analytical procedures and investigated their occurrence at a mud spring recreation area in Taiwan. We investigated factors potentially associated with the prevalence of the pathogens, including various water types, and physical and microbiological water quality parameters. Spring water was collected from 34 sites and Acanthamoeba, Hartmannella, Naegleria, and Legionella were detected in 8.8%, 35.3%, 14.7%, and 47.1%, respectively. The identified species of Acanthamoeba included Acanthamoeba castellanii and Acanthamoeba polyphaga. Nearly all the Hartmannella isolates are identified as Hartmannella vermiformis. The Naegleria species included Naegleria australiensis and its sister groups, and two other isolates referred to a new clade of Naegleria genotypes. The Legionella species identified included unnamed Legionella genotypes, Legionella pneumophila serotype 6, uncultured Legionella spp., Legionella lytica, Legionella drancourtii, and Legionella waltersii. Significant differences (Mann-Whitney U test, P < 0.05) were observed between the presence/absence of Hartmannella and total coliforms, between the presence/absence of Naegleria and heterotrophic plate counts, and between the presence/absence of Legionella and heterotrophic plate counts. This survey confirms that pathogenic free-living amoebae and Legionella are prevalent in this Taiwanese mud spring recreation area. The presence of pathogens should be considered a potential health threat when associated with human activities in spring water.     

Real-time microgravimetric quantification of Cryptosporidium parvum in the presence of potential interferents

The quartz crystal microbalance with dissipation monitoring (QCM-D) is used to develop a biosensor for detection of viable Cryptosporidium parvum (C. parvum) in water matrices of varying complexity. In a clean environment, a good log-log linear response is obtained for detection of C. parvum in aqueous suspensions with oocyst concentrations from 3 × 10⁵ to 1 × 10⁷ oocysts/mL. C. parvum detection is slightly affected by the presence of dissolved organic acids, likely due to steric stabilization and/or masking of the antibodies/antigens by adsorbed molecules. Colloidal contaminants generally have a greater influence as biosensor interferents, whereby the presence of model latex microspheres, Enterococcus faecalis, or Escherichia coli, led to decreases in biosensor response of up to 64%, 40%, and 20%, respectively.     

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.     

Influence of high gas production during thermophilic anaerobic digestion in pilot-scale and lab-scale reactors on survival of the thermotolerant pathogens Clostridium perfringens and Campylobacter jejuni in piggery wastewater

Safe reuse of animal wastes to capture energy and nutrients, through anaerobic digestion processes, is becoming an increasingly desirable solution to environmental pollution. Pathogen decay is the most important safety consideration and is in general, improved at elevated temperatures and longer hydraulic residence times. During routine sampling to assess pathogen decay in thermophilic digestion, an inversely proportional relationship between levels of Clostridium perfringens and gas production was observed. Further samples were collected from pilot-scale, bench-scale thermophilic reactors and batch scale vials to assess whether gas production (predominantly methane) could be a useful indicator of decay of the thermotolerant pathogens C. perfringens and Campylobacter jejuni. Pathogen levels did appear to be lower where gas production and levels of methanogens were higher. This was evident at each operating temperature (50, 57, 65 °C) in the pilot-scale thermophilic digesters, although higher temperatures also reduced the numbers of pathogens detected. When methane production was higher, either when feed rate was increased, or pH was lowered from 8.2 (piggery wastewater) to 6.5, lower numbers of pathogens were detected. Although a number of related factors are known to influence the amount and rate of methane production, it may be a useful indicator of the removal of the pathogens C. perfringens and C. jejuni.     

Survival of manure-borne E. coli in streambed sediment: Effects of temperature and sediment properties

Escherichia coli bacteria are commonly used as indicator organisms to designate of impaired surface waters and to guide the design of management practices to prevent fecal contamination of water. Stream sediments are known to serve as a reservoir and potential source of fecal bacteria (E. coli) for stream water. In agricultural watersheds, substantial numbers of E. coli may reach surface waters, and subsequently be deposited into sediments, along with fecal material in runoff from land-applied manures, grazing lands, or wildlife excreta. The objectives of this work were (a) to test the hypothesis that E. coli survival in streambed sediment in the presence of manure material will be affected by sediment texture and organic carbon content and (b) to evaluate applicability of the exponential die-off equation to the E. coli survival data in the presence of manure material. Experiments were conducted at three temperatures (4 °C, 14 °C, and 24 °C) in flow-through chambers using sediment from three locations at the Beaverdam Creek Tributary in Beltsville, Maryland mixed with dairy manure slurry in the proportion of 1000:1. Indigenous E. coli populations in sediments ranged from ca. 10¹ to 10³ MPN g⁻¹ while approx 10³ manure-borne E. coli MPN g⁻¹ were added. E. coli survived in sediments much longer than in the overlaying water. The exponential inactivation model gave an excellent approximation of data after 6-16 days from the beginning of the experiment. Slower inactivation was observed with the increase in organic carbon content in sediments with identical granulometric composition. The increase in the content of fine particles and organic carbon in sediments led not only to the slower inactivation but also to lower sensitivity of the inactivation to temperature. Streambed sediment properties have to be documented to better evaluate the role of sediments as reservoirs of E. coli that can affect microbiological stream water quality during high flow events.     

Degradation of yew, ragwort and rhododendron toxins during composting

Recent concerns have been raised that plants such as ragwort (Senecio jacobaea), yew (Taxus baccata) and rhododendron (Rhododendron ponticum) that are toxic to livestock may be included in compost windrows but may not be fully detoxified by the composting process. This study investigates the decomposition during composting of toxic pyrrolizidine alkaloids present in ragwort, taxines (A and B) present in yew, and grayanotoxins (GTX I, II, and III) present in rhododendron during composting. Plant samples were contained within microporous bags either towards the edge or within the centre of a pilot-scale compost heap. They were destructively harvested at regular intervals over 1200 °C cumulative temperature (about three months). Samples were analysed for levels of toxins by liquid chromatography time of flight mass spectrometry (LC-TOF-MS). Pyrrolizidine alkaloids and taxines were shown to degrade completely during the composting process. While GTX I showed significant reductions, concentrations of GTX III remained unchanged after 1200 °C cumulative temperature. However, estimates of exposure to grazing livestock coming into contact with source-segregated green waste compost containing up to 7% rhododendron suggest that GTX III poses no appreciable risk.     

Inhalation method for delivery of nanoparticles to the Drosophila respiratory system for toxicity testing

The growth of the nanotechnology industry and subsequent proliferation of nanoparticle types present the need to rapidly assess nanoparticle toxicity. We present a novel, simple and cost-effective nebulizer-based method to deliver nanoparticles to the Drosophila melanogaster respiratory system, for the purpose of toxicity testing. FluoSpheres®, silver, and CdSe/ZnS nanoparticles of different sizes were effectively aerosolized, showing the system is capable of functioning with a wide range of nanoparticle types and sizes. Red fluorescent CdSe/ZnS nanoparticles were successfully delivered to the fly respiratory system, as visualized by fluorescent microscopy. Silver coated and uncoated nanoparticles were delivered in a toxicity test, and induced Hsp70 expression in flies, confirming the utility of this model in toxicity testing. This is the first method developed capable of such delivery, provides the advantage of the Drosophila health model, and can serve as a link between tissue culture and more expensive mammalian models in a tiered toxicity testing strategy.     

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.