Poster Presentations

Session Title: Biodegradation: Appetite for the Unusual
Presentation Date: Thursday, August 21, 2008
Poster Board Number: 0031

EVIDENCE FOR NOVEL DECHLORINATORS CONTRIBUTING CHLORINATED ETHENE DETOXIFICATION

D.B. Meisinger¹, M. Pavlekovic¹, K.U. Totsche², V. Radl³, M. Schloter³, M. Schmid⁴, K. Ritalahti⁵, F.E. Löffler⁵, N. Lee^1
1Technical University of Munich, Microbiology, Freising, Germany, ²Friedrich Schiller University of Jena, Geosciences, Jena, Germany, ³Helmholtz Zentrum München, Soil Ecology, Neuherberg, Germany, ⁴Helmholtz Zentrum München, Plant Microbe Interactions, Neuherberg, Germany, ⁵Georgia Institute of Technology, Environmental Microbiology and Engineering, Atlanta, United States of America

Chloroorganic compounds such as chlorinated ethenes are widespread environmental pollutants, which can be detoxified by reductively dechlorinating bacteria. However, depending on species, different degradation reactions may occur, some of them yielding more toxic products such as VC. Thus, for a successful bioremediation, detailed knowledge about the composition of dechlorinating assemblages is required. Here, we describe the native microbial community associated with a TCE and BTEX contaminated aquifer in Southern Germany where significant in situ reductive dechlorination to ethene occurs. We applied a comprehensive approach encompassing: i) 16S and 18S rRNA clone libraries; ii) isolation; iii) screening of known dechlorinaters by DGGE, nested PCR, qPCR and FISH by targeting both 16S rRNA and reductive dehalogenase genes. Screening of 800 16S rRNA gene clones yielded 10 different phyla, encompassing mostly not-yet-cultured representatives affiliated with the Chloroflexi, Deltaproteobacteria, Firmicutes, etc., and different novel candidate groups. In addition, 115 isolates were retrieved, which were not represented the 16S rRNA gene clone library. Screening of 140 18S rRNA clones yielded 11 phyla, encompassing mostly not-yet-cultured fungal representatives. The application of nucleic acid-based tools targeting known dechlorinators revealed the presence of Geobacter spp. at low (2 %per liter of groundwater) cell titers. Dehalococcoides were only detected with nested PCR suggesting that these bacteria were present but in such low numbers that the observed in situ dechlorination reactions are likely catalyzed by other, not yet identified bacteria. These findings suggest that the site may contain novel dechlorinators capable of chlorinated ethene detoxification.