Dechlorination of three tetrachlorobenzene isomers by contaminated harbor sludge-derived enrichment cultures follows thermodynamically favorable reactions

Yue Lu, Javier Ramiro-Garcia, Pieter Vandermeeren, Steffi Herrmann, Danuta Cichocka, Dirk Springael, Siavash Atashgahi, Hauke Smidt*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

8 Citations (Scopus)

Abstract

Dechlorination patterns of three tetrachlorobenzene isomers, 1,2,3,4-, 1,2,3,5-, and 1,2,4,5-TeCB, were studied in anoxic microcosms derived from contaminated harbor sludge. The removal of doubly, singly, and un-flanked chlorine atoms was noted in 1,2,3,4- and 1,2,3,5-TeCB fed microcosms, whereas only singly flanked chlorine was removed in 1,2,4,5-TeCB microcosms. The thermodynamically more favorable reactions were selectively followed by the enriched cultures with di- and/or mono-chlorobenzene as the main end products of the reductive dechlorination of all three isomers. Based on quantitative PCR analysis targeting 16S rRNA genes of known organohalide-respiring bacteria, the growth of Dehalococcoides was found to be associated with the reductive dechlorination of all three isomers, while growth of Dehalobacter, another known TeCB dechlorinator, was only observed in one 1,2,3,5-TeCB enriched microcosm among biological triplicates. Numbers of Desulfitobacterium and Geobacter as facultative dechlorinators were rather stable suggesting that they were not (directly) involved in the observed TeCB dechlorination. Bacterial community profiling suggested bacteria belonging to the phylum Bacteroidetes and the order Clostridiales as well as sulfate-reducing members of the class Deltaproteobacteria as putative stimulating guilds that provide electron donor and/or organic cofactors to fastidious dechlorinators. Our results provide a better understanding of thermodynamically preferred TeCB dechlorinating pathways in harbor environments and microbial guilds enriched and active in anoxic TeCB dechlorinating microcosms.

Original languageEnglish
Pages (from-to)2589-2601
JournalApplied Microbiology and Biotechnology
Volume101
Issue number6
DOIs
Publication statusPublished - 2017

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Keywords

  • Dehalobacter
  • Dehalococcoides mccartyi
  • Organohalide respiration
  • Tetrachlorobenzenes
  • Thermodynamically favorable reactions

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