Ecotoxicity characterization assisted performance assessment of electro-bioremediation reactors for nitrate and arsenite elimination.

The performance of combined reduction of nitrate (NO3 - ) to dinitrogen gas (N2 ) and oxidation of arsenite (As[III]) to arsenate (As[V]) by a bioelectrochemical system was assessed, supported by ecotoxicity characterization. For the comprehensive toxicity characterization of the untreated model groundwater and the treated reactor effluents, a problem-specific ecotoxicity test battery was established. The performance of the applied technology in terms of toxicity and target pollutant elimination was compared and analyzed. The highest toxicity attenuation was achieved under continuous flow mode with hydraulic retention time (HRT) = 7.5 h, with 95%, nitrate removal rate and complete oxidation of arsenite to arsenate. Daphnia magna proved to be the most sensitive test organism. The results of the D. magna lethality test supported the choice of the ideal operational conditions based on chemical data analysis. The outcomes of the study demonstrated that the applied technology was able to improve the groundwater quality in terms of both chemical and ecotoxicological characteristics. The importance of ecotoxicity evaluation was also highlighted, given that significant target contaminant elimination did not necessarily lower the environmental impact of the initial, untreated medium, in addition, anomalies might occur during the technology operational process which in some instances, could result in elevated toxicity levels.

Biofilm development of Candida boidinii and the effect of tyrosol on biofilm formation.

OBJECTIVES: The applicability of a simple and high-throughput method for quantitative characterization of biofilm formation by Candida boidinii was tested in order to evaluate the effects of exogenous tyrosol on yeast growth and biofilm formation capacity. RESULTS: Significant concentration-, temperature and time-dependent effect of tyrosol (2-(4-hydroxyphenyl)ethanol) was demonstrated, but it differentially affected the growth and biofilm formation (characterized by crystal violet staining and XTT-reduction assay) of Candida boidinii. Testing biofilm based on metabolic activity displayed sensitively the differences in the intensity of biofilm in terms of temperature, tyrosol concentration, and exposure time. At 22 °C after 24 h none of the tyrosol concentrations had significant effect, while at 30 °C tyrosol-mediated inhibition was observed at 50 mM and 100 mM concentration. After 48 h and 72 h at 22 °C, biofilm formation was stimulated at 6.25-25 mM concentrations, meanwhile at 30 °C tyrosol decreased the biofilm metabolic activity proportionally with the concentration. CONCLUSIONS: The research concludes that exogenous tyrosol exerts unusual effects on Candida boidinii growth and biofilm formation ability and predicts its potential application as a regulating factor of various fermentations by Candida boidinii.

Cyclodextrin-mediated quorum quenching in the Aliivibrio fischeri bioluminescence model system - Modulation of bacterial communication.

Bacterial Quorum Sensing is a cell-to-cell communication process, in which, bacteria, performing cooperative behaviour, produce and detect extracellular signalling chemicals, to monitor cell population density. Numerous bacterial processes including bioluminescence, virulence factor production, biofilm formation etc. are known to be influenced by this bacterial communication network. Interest in QS systems has emerged in response to the fact that these processes have significant impact on the environment, human health as well as agriculture. Cyclodextrins-mediated quorum quenching is an innovative approach and the available information about their effects is very scarce. We selected Aliivibrio fischeri, a bacterium, producing light, based on Quorum Sensing, to be the first to investigate the cyclodextrins' effect on this bioluminescence. A systematic study was performed with twelve different cyclodextrin compounds in order to determine their concentration- and time-dependent bioluminescence inhibitory effect in the A. fischeri model system. Especially high quorum quenching effect was found for α-cyclodextrin: 10 mM α-cyclodextrin at 120 min contact time which caused ~64% inhibition of bioluminescence. Experiments with the co-administration of α-cyclodextrin and N-(3-oxohexanoyl)-L-homoserine lactone, the signalling molecule of A. fischeri clearly showed, that the stimulating effect of this signal was diminished by α-cyclodextrin, suggesting, that complexation was responsible for the observed Quorum Sensing suppression. Although ß-cyclodextrin and its hydroxypropyl derivative significantly inhibited bioluminescence at as low as 0.156 mM concentration, their efficiency did not reach the level of α-cyclodextrin. According to our results, the autoinducer-dependent quorum sensing mechanism in Aliivibrio fischeri was markedly inhibited, the quorum quenching effect of cyclodextrins was clearly demonstrated. The efficiency was influenced by several parameters; the size of the interior cavity, the structure and the concentration of the cyclodextrins, as well as the contact time with the cells. The application of a cyclodextrin-trap for complexation of signal molecules may be a novel, promising method for influencing QS interfering strategies, for example, to enhance the efficiency of various biotechnologies, as well as to find alternative approaches against bacterial proliferation and infections. Furthermore, our results could also serve as a basis for further research with bacterial or plant model systems, in which the same chemical signals may induce physiological responses.

Ecotoxicity Assessment of Graphene Oxide by Daphnia magna through a Multimarker Approach from the Molecular to the Physiological Level including Behavioral Changes.

The extensive use of engineered nanomaterials, such as graphene oxide (GO), is stimulating research about its potential environmental impacts on the aquatic ecosystem. This study is aimed to comprehensively assess the acute toxicity of a well-characterized GO suspension to Daphnia magna. Conventional ecotoxicological endpoints (lethality, immobilization) and more sensitive, sublethal endpoints (heartbeat rate, feeding activity, and reactive oxygen species (ROS)) production were used. The possible normalization of the heartbeat rate and feeding activity in clean test medium was also investigated. The fate, time-dependent, and concentration-dependent aggregation behaviour of GO was followed by dynamic light scattering, UV-Vis spectroscopy, and zeta potential measurement methods. The EC20 value for immobilization was 50 mg/L, while, for physiological and behavioural endpoints, it ranged from 8.1 mg/L (feeding activity) to 14.8 mg/L (immobilization). The most sensitive endpoint was the ROS production with EC20 = 4.78 mg/L. 24-h recovery experiments revealed that feeding activity was restored only up to a certain level at higher concentrations, indicating that the potential environmental health effects of GO cannot be neglected. Alterations of normal physiology (heart rate) and feeding activity may be associated with increased risk of predation and reproductive decline, highlighting that GO may have impacts on population and food web dynamics in aquatic ecosystems.

Demonstration of Radiographic Bone Fill in Postextraction Sockets Using a Novel Implant-Site Development Technique: A Retrospective Comparative Case Series.

The objective of this study was to compare the novel extraction-site development (XSD) technique with spontaneous healing. Advanced alveolar defects (extraction defect sounding, classes 3 and 4) at 33 single-rooted teeth were treated by XSD (test), and 21 extraction sites of single-rooted teeth were left for spontaneous healing (control). In pre- and postoperative cone beam computed tomography (CBCT) data sets, orovestibular and vertical socket dimensions were assessed, as were socket areas. XSD resulted in complication-free healing with significantly higher radiographic bone fill compared to spontaneous healing. Application of the XSD approach may reduce the need for augmentative procedures during implant placement.

[Treating tissue defects following tooth removal. Three case reports]. / Fogeltávolítást követoen visszamaradt szöveti defektus ellátása. Három eset ismertetése.

Following tooth removal, three dimensional hard- and soft-tissue loss take place. Spontaneous healing makes the defect more severe and results in collapsing tissues. Implant placement is not feasible. In the aestethic zone even fixed partial dentures will not deliver the expected result. Our aim was to demonstrate that only ridge preservation enables implant placement and also provides excellent aestetic result even at frontal areas. CBCT was made before and 6-8 months after ridge preservation. Vertical and socket area measurements were carried out and compared in pre-, and postoperative images. Implant placement was feasible in all three cases; furthermore favourable buccal bone (4.24 mm, 6.22 mm, 9.57 mm) and area growth (129%, 145%, 167%) were measured. Ridge preservation provides appropriate therapy for complete reconstruction of tissues after tooth removal. Orv Hetil. 2017; 158(31): 1228-1234.