Analysis and comparison of the microbial community structures of two enrichment cultures capable of reductively dechlorinating TCE and cis-DCE
Article first published online: 20 NOV 2003
Volume 6, Issue 1, pages 45–54, January 2004
How to Cite
Gu, A. Z., Hedlund, B. P., Staley, J. T., Strand, S. E. and Stensel, H. D. (2004), Analysis and comparison of the microbial community structures of two enrichment cultures capable of reductively dechlorinating TCE and cis-DCE. Environmental Microbiology, 6: 45–54. doi: 10.1046/j.1462-2920.2003.00525.x
- Issue published online: 20 NOV 2003
- Article first published online: 20 NOV 2003
- Received 28 April, 2003; accepted 27 August, 2003.
In order to study the effect of different chloroethenes (electron acceptors) on the bacterial composition of dechlorinating communities, two reductive dechlorinating enrichment cultures were developed that were able to reduce trichloroethene (TCE) and cis-1,2-dichloroethene (cis-DCE) to ethene using hydrogen as electron donor, respectively. The inoculum for the cultures was material from a methanogenic fluidized bed reactor (FBR), which was originally seeded with digester sludge and showed a stable capacity for tetrachloroethene (PCE) reduction to ethene for over six years. Molecular methods were used to determine and compare the microbial communities of these two enrichment cultures. A clone library of bacterial 16S rRNA genes was generated for each enrichment. The clones were screened into different groups by restriction fragment length polymorphism (RFLP) analysis using two different four base pair recognition restriction enzymes. A total of 12 sequence types were identified by phylogenetic analysis of nearly complete 16S rDNA sequences (∼1450 bp). The sequences were affiliated with six recognized phyla of the domain Bacteria: Firmicutes (low G+C Gram-positives), Chloroflexi (green non-sulphur bacteria), Actinobacteria (high G+C Gram-positives), Bacteroidetes (Cytophaga-Flexibacter-Bacteroides), Nitrospira and Spirochaetes. The results led to the identification of an organism closely related to Dehalococcoides ethenogenes to be the presumptive dechlorinator in both enrichments. Different electron acceptors affected the bacterial diversity and the community profiles of the two enrichments. Most of the sequences identified in our dechlorinating enrichments shared high similarities with sequences previously obtained from other enriched dechlorinating cultures and chlorinated-compound-contaminated sediments or aquifers, suggesting these bacteria may have direct or indirect roles in reductive dechlorination.