Schadstoffabbau als Atmungsprozess, Reduktive Dehalogenierung Alfredo Pérez-de-Mora Institute of Groundwater Ecology Helmholtz Zentrum Munich contact:

OUTLINE Organism of the day Characteristics of Dehalococcoides Reductive dechlorination Toxicity of chlorinated compounds Chemical properties of chlorinated compounds Groundwater contamination Remediation technologies for Volatile Organic Contaminants How to monitor reductive dechlorination in the field 2 problems

Organismus des Tages Dehalococcoides mccartyi D. ethenogenes now D.maccartyi strain 195 Maymo-Gatell et al., Science 1997

Chronology of Dehalococcoides 1989 D. Freedmann and J. Gossett –First enrichments showing transformation of PCE to ethene 1997 Isolation Maymo-Gatell and Steve Zinders - Degrades PCE to VC and Ethene 2002 First field demonstration of bioaugmentation (KB-1 culture) Isolation of other strains 2000 strain CBDB1 grows on clorinated aromatics 2003 strains bav1 and VS grow on cDCE and VC as TEA 2005 strain FL2 grows metabolically on TCE and cDCE, but cometabolically on VC 2006 strain GT degrades TCE all the way to ethene 2005 Genome of D. ethenogenes sequenced

Löffler et al., Int J Sys Evol Microbiol 2013 Particular compartmentalization for Gram negative Morphology of Dehalococcoides

Revisiting bacterial classification

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Alternative to Gram staining Monoderm Diderm Revisiting bacterial classification Chloroflexi and Dehalococcoides Monoderms Gram negative

Organismus des Tages Dehalococcoides mccartyi (Notes on phylogeny) Phylum Chloroflexi

Organismus des Tages Dehalococcoides ethenogenes Domäne: Eubacteria Phylum: Chloroflexi Gattung: Dehalococcoides Löffler et al., Int J Sys Evol Microbiol 2013 Phylum Chloroflexi

Features of Dehalococcoides metabolism H 2 as electron donor Chlorinated compound as TEA Acetate as C source Incomplete TCA cycle CO 2 fixation pathway Incomplete cobalamin synthesis pathway Cannot synthesize methionine (all other aa yes)

Working with dechlorinating cultures

What is so special about Dehalococcoides? Reductive dechlorination = organohalide respiration C C Cl C C H C C HH C C H HH C C HH HH PCETCE cDCE VCethene Dehalococcoides Geobacter Dehalobacter Desulfitobacterium Sulfurospirillum Organochlorine compounds as TEAs

The mechanism: Reductive dehalogenation

Hydro- genase e- carrier Dehalo- genase ATPase H2H2 2H + 2e - nH + ethene + 3HCl TCE + 6H + + 6e - ADP + Pi ATP Cytosol Redesigned from Reshandri et al Science The mechanism: Reductive dehalogenation H+H+ TCE S - layer Periplasm ethene 2e -

Cobalamine mediated reduction of DCE and VC From Glod et al., 1997 EST

The catalyst: reductive dehalogenases HPR: Hyper Variable Regions McMurdie et al PLOSone Genetics

The energetics of reductive dehalogenation Problem: Calculate the change in free energy (KJ/e-eq) for the reductive dechlorination of: TCE to ethene VC to ethene

Chlorinated solvents properties