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Initial project plan

State of the art and preliminary work

Organic trace pollutants are regularly detected in both surface and groundwater systems. Many of these compounds, including pharmaceuticals, exert biological activities, and thus may affect organisms in the environment even when the concentrations of these pollutants are very low. However, it has to be pointed out that the type of biological action in the environment may be completely different from what is to be intended, partly because of the large differences in concentration between the environment and the human body. Furthermore, organisms may be affected if they have not yet been considered to be sensitive to these biologically active compounds (Schreiber & Szewzyk 2008). In general, the microbial degradation of organic trace pollutants is still insuffiently understood. A major question is whether the pollutants occuring in very low concentrations are degraded by specialised bacteria or if co-metabolism is the major mechanism causing degradation. Given the low environmental concentrations of these compounds, effective degradation requires continuous flow conditions and immobilised microorganisms at interfaces. Our own unpublished analyses of the degradation of a common pharmaceutical paracetamol indicate that current paradigms need to be revised. While previous studies reported that paracetamol was not completely degraded, we have found out that the compound is transformed (by the same microbial species) to substances which show characteristics resembling those of humic substances. Several studies have already demonstrated the degradation of pharmaceuticals in various habitats (Xu et al. 2011, De Weert et al. 2010, Ramil et al. 2010, Quintana et al. 2005, Groning et al. 2007, Kunkel & Radtke 2008, van der Bas et al. 2009). Our own investigations have shown the degradation of phenazone and metamizole by natural biofilms (Pieper et al. 2010) and recently, the potential of many strains of iron bacteria revealed to degrade diclofenac and carbamazepine.

Aims and work steps

The aim of this thesis is to study the potential of both defined and natural biofilm communities to degrade (recalcitrant) pollutants such as paracetamol, diclofenac, carbamazepine and iodinated contrast media of urban water systems. It focuses on biofilms forming at various solid-water interfaces and consisting of both aerobic and anaerobic subpopulations capable of promoting multiple degradation pathways and strategies. A variety of biofilm reactors and long standing experience in their operation and examination are available. Different reactors will be used for testing organic removal rates and documenting the accumulation of microbial populations. The microbial populations will be examined by physiological tests and molecular methods (454 sequencing, FISH, CLSM, DGGE, qPCR). In addition, a large collection of freshwater and ironbacteria available in culture will be tested for their degradation potential. The aim is to evaluate if the pollutant-degrading organisms can live on trace pollutants alone or if they require cosubstrates to maintain their energy metabolism. We will also assess the significance of interactions (syntrophy, co-metabolism) between organisms for determining degradation efficiency. We are especially interested to what extent the pharmaceuticals are transformed to compounds which can be integrated in the pool of natural humic substances. After having identified the pollutant-degrading organisms, specific tools (FISH, qPCR) will be used to detect and quantify them in both laboratory reactors and natural biofilms.

Connections to interfaces and other doctoral theses

There will be cooperation with N4 and N5 on the flux of substances across the aerobic/anaerobic boundary and the characterisation of microbial populations in the respective microhabitats. In collaboration with T2, specific FISH probes will be set up to investigate sulphur-oxidising bacteria in sewer biofilms. Data on degradation kinetics, turnover rates and locations of turnover processes provide important information which can be implemented in the model developed in N7. There are further linkages to T6 on biodegradation and to N6 which investigates similar processes in the hyporheic zone. 

 

References

De Weert.J., Vinas,M., Grotenhuis,T., Rijnaarts,H. & Langenhoff,A. (2010): Aerobic nonylphenol degradation and nitro-nonylphenol formation by microbial cultures from sediments. Appl Microbiol Biotechnol 86:761-771

Groning,J., Held,C., Garten,C., Claussnitzer, U., Kaschabek, S.R. & Schlömann,M. (2007): Transformation of diclofenac by the indigenous microflora of river sediments and identification of a major intermediate. Chemosphere 69:509-516

Kunkel,U., Radke,M. (2008): Biodegradation of acidic pharmaceuticals in bed sediments: insight from a laboratory experiment. Environ Sci Technol 42:7273-7279

Pieper,C., Risse,D., Schmidt,B., Braun,B., Szewzyk,U. & Rotard,W. (2010): Investigation of the microbial degradation of phenazone-type drugs and their metabolites by natural biofilms derived from river water using liquid chromatography/tandem mass spectrometry (LCMS/MS). Water Res. 44:4559-4569

Quintana,J.B., Weiss,S. & Reemtsma,T. (2005): Pathways and metabolites of microbial degradation of selected acidic pharmaceutical and their occurrence in municipal wastewater treated by a membrane bioreactor. Water Res 39:2654-2664

Ramil,M., El,A.T., Fink,G., Scheurer,M. &Ternes,T.A. (2010): Fate of beta blockers in aquaticsediment systems: sorption and biotransformation. Environ Sci Technol 44:962-970

Schreiber,F. & Szewzyk,U. (2008): Environmentally relevant concentrations of pharmaceuticals influence the initial adhesion of bacteria. Aquatic Toxicol., 87, 227-233

Van der Bas,Z., De Weert.J., Rijnaarts,H., de Vos, W.M., Smidt,H. & Gerritse,J. (2009): Degradation of 1,2-dichloroethane by microbial communities from river sediment at various redox conditions. Water Res 43:3207-3216

Xu,B., Mao,D., Luo,Y. & Xu,L. (2011): Sulfamethoxazole biodegradation and biotransformation in the water-sediment system of a natural river. Bioresour Technol 102:7069-7076

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