Stanislav Smrček

Phytoremediation of polyaromatic hydrocarbons, anilines and phenols.

Phytoremediation technologies based on the combined action of plants and the microbial communities that they support within the rhizosphere hold promise in the remediation of land and waterways contaminated with hydrocarbons but they have not yet been adopted in large-scale remediation strategies. In this review plant and microbial degradative capacities, viewed as a continuum, have been dissected in order to identify where bottlenecks and limitations exist. Phenols, anilines and polyaromatic hydrocarbons (PAHs) were selected as the target classes of molecule for consideration, in part because of their common patterns of distribution, but also because of the urgent need to develop techniques to overcome their toxicity to human health.Depending on the chemical and physical properties of the pollutant, the emerging picture suggests that plants will draw pollutants including PAHs into the plant rhizosphere to varying extents via the transpiration stream. Mycorrhizosphere-bacteria and -fungi may play a crucial role in establishing plants in degraded ecosystems. Within the rhizosphere, microbial degradative activities prevail in order to extract energy and carbon skeletons from the pollutants for microbial cell growth. There has been little systematic analysis of the changing dynamics of pollutant degradation within the rhizosphere; however, the importance of plants in supplying oxygen and nutrients to the rhizosphere via fine roots, and of the beneficial effect of microorganisms on plant root growth is stressed.In addition to their role in supporting rhizospheric degradative activities, plants may possess a limited capacity to transport some of the more mobile pollutants into roots and shoots via fine roots. In those situations where uptake does occur (i.e. only limited microbial activity in the rhizosphere) there is good evidence that the pollutant may be metabolised. However, plant uptake is frequently associated with the inhibition of plant growth and an increasing tendency to oxidant stress. Pollutant tolerance seems to correlate with the ability to deposit large quantities of pollutant metabolites in the ‘bound’ residue fraction of plant cell walls compared to the vacuole. In this regard, particular attention is paid to the activities of peroxidases, laccases, cytochromes P450, glucosyltransferases and ABC transporters. However, despite the seemingly large diversity of these proteins, direct proof of their participation in the metabolism of industrial aromatic pollutants is surprisingly scarce and little is known about their control in the overall metabolic scheme. Little is known about the bioavailability of bound metabolites; however, there may be a need to prevent their movement into wildlife food chains. In this regard, the application to harvested plants of composting techniques based on the degradative capacity of white-rot fungi merits attention.

Plant response to heavy metals and organic pollutants in cell culture and at whole plant level

In vitro cell culture experiments provide a convenient system to study basic biological processes, by which biochemical pathways, enzymatic activity and metabolites can be specifically studied. However, it is difficult to relate cell cultures, calli or even hydroponic experiments to the whole plant response to pollutant stress. In the field, plants are exposed to additional a-biotic and biotic factors, which complicate further plant response. Hence, we often see thatin vitro selected species perform poorly under soil and field conditions. Soil physical and chemical properties, plantmycorrhizal association and soil-microbial activity affect the process of contaminant degradation by plants and/or microorganisms, pointing to the importance of pot and field experiments.BackgroundIncreasing awareness in the last decade concerning environmental quality had prompted research into ‘green solutions’ for soil and water remediation, progressing from laboratoryin vitro experiments to pot and field trials.ObjectiveThis paper is a joint effort of a group of scientists in COST action 837. It represents experimental work and an overview on plant response to environmental stress fromin vitro tissue culture to whole plant experiments in soil.ResultsResults obtained fromin vitro plant tissue cultures and whole plant hydroponic experiments indicate the phytoremediation potential of different plant species and the biochemical mechanisms involved in plant tolerance. In pot experiments, several selected desert plant species, which accumulated heavy metal in hydroponic systems, succeeded in accumulating the heavy metal in soil conditions as well.Conclusions and RecommendationsIn vitro plant tissue cultures provide a useful experimental system for the study of the mechanisms involved in the detoxification of organic and heavy metal pollutants. However, whole plant experimental systems, as well as hydroponics followed by pot and field trials, are essential when determining plant potential to remediate polluted sites. Multidisciplinary research teams can therefore increase our knowledge and promote a practical application of phytoremediation.

Structural requirements for inhibitors of cytochromes P450 2B: assessment of the enzyme interaction with diamondoids.

The series of diamondoids: adamantane, diamantane, triamantane, 2-isopropenyl-2-methyladamantane and 3-isopropenyl-3-methyldiamantane (3-IPMDIA), were employed to elucidate the molecular basis of their interaction with the active site of cytochromes P450 (CYP) of a 2B subfamily. These potent inhibitors of CYP2B enzymes were docked into the homology model of CYP2B4. Apparent dissociation constants calculated for the complexes of CYP2B4 with docked diamandoids agreed closely with the experimental data showing inhibition potency of the compounds and their binding affinity to CYP2B4. Superimposed structures of docked diamondoids mapped binding site residues. As they are mainly non-polar residues, the hydrophobicity plays the major role in the binding of diamondoids. Overlapping structure of diamondoids defined an elliptical binding cavity (5.9 Å inner diameter, 7.9 Å length) forming an angle of ∼43° with the heme plane. CYP2B specific diamondoids, namely 3-IPMDIA, showing the highest binding affinity, should be considered for a potential clinical use.

PHYTOREMEDIATION OF EXPLOSIVES IN TOXIC WASTES

Selected emergent plants (helophytes) Phragmites australis, Juncus glaucus, Carex gracillis and Typha latifolia were successfully used for degradation of TNT (2,4,6-trinitrotoluene) under in vitro conditions. The plants took up and transformed more than 90% of TNT from the medium within ten days of cultivation. The most efficient species was Ph. australis which took up 98% of TNT within ten days. The first stable degradation products 4-amino-2,6- dinitrotoluene (4-ADNT) and 2-amino-4,6-dinitrotoluene (2-ADNT) were identified and quantified. TNT degradation products and their compartmentalization in plant tissues were evaluated after two weeks of cultivation using ( 14 C) TNT. Forty one percent of 14 C was detected as insoluble or bound in cell structures: 34% in roots and 8% in the aerial parts. The results were verified in pilot constructed wetland for cleaning explosive containing waste-waters as a necessary step prior real scale-up application.

Environmental Aspects of Radiopharmaceuticals Extraction and Translocation of Ra 223 in Plants

Radiopharmaceuticals represent an attractive and efficient treatment of oncological diseases. Medical radionuclide use might bring a particular safety issue with penetration of a radioactive material into environment via urinal and colonal excretion. Therefore, the waste water cleaning and decontamination of food chain ought to be studied. Radium-223 is FDA and EMA approved therapeutic radionuclide for the treatment of bone metastases originating from castration resistant prostate cancer. Its introduction to clinical praxis opened the possibility of Radium retention and translocation into roots and shoot plant parts in the ecosystem. Though Ra uptake was investigated in vitro on cultivated plants Avena sativa and Zea mays using electronic autoradiography. Stimulators (Atonik, Racine, Rexan, Sunagreen, Stimulator Z) increasing the water transport, the plant stress management additives (Vermaktiv Stimul and Vermaktiv RP), together with the chelating agent ethylenediaminetetraacetic acid (EDTA) were added to the cultivars. Results of plants growth without any regulators indicate over 90% uptake of Ra in root system with minimal translocation into other parts. An addition of growth regulators decreased the overall uptake, however significantly increased Radium translocation into shoot parts. Surprisingly, an addition of EDTA decreases the overall retention in oat under the lowest detectable limit, nevertheless an increased translocation to shoot parts was observed. Experiments reveal potential of phytoextraction technologies for waste water cleaning in hospitals, on the other hand, indicates possibility of food chain contamination particularly when growth regulators were used. Keywords—uptake, radium-223, radiopharmaceuticals. environment contamination