Geochemistry and microbial diversity of a trichloroethene-contaminated Superfund site undergoing intrinsic in situ reductive dechlorination

Abstract

This study explored the geochemistry and microbial diversity of a Superfund site containing trichloroethene (TCE) and an unusual copollutant, tetrakis(2-ethylbutoxy)silane. Geochemical analysis of contaminated groundwater indicated subsurface anaerobiosis, reductive dechlorination of TCE to predominantly cis-1,2-dichloroethene, and (transient) accumulation of 2-ethylbutanol and 2-ethylbutyrate as a result of tetrakis(2-ethylbutoxy)silane breakdown. Comparative analysis of 106 16S rDNA and 61 16S^23S rDNA intergenic spacer region sequences^obtained from pristine and contaminated groundwater via DNA extraction, PCR amplification, cloning and sequencingr evealed that the contaminated groundwater featured (i) a distinct microbial community, (ii) reduced species diversity, (iii) various anaerobes, and (iv) bacteria closely related to the TCE-dechlorinating, dichloroethene-accumulating genus Dehalobacter, whereas (v) the TCE-dechlorinating, ethene-producing species Dehalococcoides ethenogenes was not detectable. Thus, geochemical and molecular biological results were in excellent agreement in this first ecological field study linking in situ reductive dechlorination of TCE to metabolism of tetraalkoxysilanes. ß

Molecular Characterization of a Dechlorinating Community Resulting from In Situ Biostimulation in a Trichloroethene-Contaminated Deep, Fractured Basalt Aquifer and Comparison to a Derivative Laboratory Culture

“…Another 13 clones appeared to be affiliated with the proposed phyla OP11 and OP3, of which, to our knowledge, there are currently no isolated representatives (61). Clones TANB22 and TANB37 had high sequence similarity with clone d153, recovered from a TCE-contaminated site undergoing natural attenuation (50). The remaining phylotypes were most similar to species of Bacteroides, Spirochaetes, Mollicutes, and Proteobacteria.…”

“…The TAN groundwater community had many similarities with those of other dechlorinating sites. Although not as dominant as they were at TAN, Clostridia were also present in an aquifer where TCE was being intrinsically degraded predominantly to cis-DCE at the Lawrence Livermore National Laboratory (50), in an aquifer undergoing intrinsic natural attenuation of hydrocarbons and chlorinated alkanes at Wurtsmith Air Force Base (14), and in a predominantly Fe(III)-reducing TCE-contaminated aquifer (36,85). All three of these other sites also had members of candidate division OP11, and the two of the three sites where complete declorination was observed had green nonsulfur Bacteria (the group to which Dehalococcoides is most similar).…”

Chimeric 16S rDNA sequences of diverse origin are accumulating in the public databases

“…One of the three unpublished studies addressed in this paper has now been published (Lowe et al, 2002; sequences d011 and d035 in Table 1). …”

High diversity of bacterial mercuric reductase genes from surface and sub-surface floodplain soil (Oak Ridge, USA)

“…Most of the studies dealing with heavy metal contamination in soil have been conducted with surface soils (Rasmussen and Sørensen, 2001;Muller et al, 2001a;Muller et al, 2001b;Ellis et al, 2003), whereas only few studies have looked at sub-surface soils, and most of these have dealt with other metals, for example, uranium (North et al, 2004;Abulencia et al, 2006) or organic pollutants (Lowe et al, 2002;Zhou et al, 2004).…”