Bacterial diversity of an acidic Louisiana groundwater contaminated by dense nonaqueous-phase liquid containing chloroethanes and other solvents

doi:10.1111/j.1574-6941.2006.00146.x

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Wiley InterScience

FEMS Microbiology Ecology

Volume 58 Issue 1, Pages 120 - 133

Published Online: 8 May 2006

Published on behalf of the Federation of European Microbiological Societies

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Bacterial diversity of an acidic Louisiana groundwater contaminated by dense nonaqueous-phase liquid containing chloroethanes and other solvents

Kimberly S. Bowman ¹ , William M. Moe ¹ , Brian A. Rash ² , Hee-Sung Bae ² & Fred A. Rainey ²

¹ Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA, USA; and ² Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, USA

Correspondence: William M. Moe, 3418G CEBA Building, Department of Civil and Environmental Engineering, Louisiana State University, Baton Rouge, LA 70803, USA. Tel.: +225 578 9174; fax: +225 578 8652; e-mail: moemwil@lsu.edu

Editor: Max Häggblom

KEYWORDS

bioremediation • chlorosolvents • 'Dehalococcoides' • DNAPL • reductive dechlorination

ABSTRACT

Bacterial concentration and diversity was assessed in a moderately acidic (pH 5.1) anaerobic groundwater contaminated by chlorosolvent-containing DNAPL at a Superfund site located near Baton Rouge, Louisiana. Groundwater analysis revealed a total aqueous-phase chlorosolvent concentration exceeding 1000 mg L⁻¹, including chloroethanes, vinyl chloride, 1,2-dichloropropane, and hexachloro-1,3-butadiene as the primary contaminants. Direct counting of stained cells revealed more than 3 × 10⁷ cells mL⁻¹ in the groundwater, with 58% intact and potentially viable. Universal and 'Dehalococcoides'-specific 16S rRNA gene libraries were created and analyzed. Universal clones were grouped into 18 operational taxonomic units (OTUs), which were dominated by low-G+C Gram-positive bacteria (62%) and included several as yet uncultured or undescribed organisms. Several unique 16S rRNA gene sequences closely related to Dehalococcoides ethenogenes were detected. Anaerobically grown isolates (168 in total) were also sequenced. These were phylogenetically grouped into 18 OTUs, of which only three were represented in the clone library. Phylogenetic analysis of isolates and the clone sequences revealed close relationships with dechlorinators, fermenters, and hydrogen producers. Despite acidic conditions and saturation or near-saturation chlorosolvent concentrations, the data presented here demonstrate that large numbers of novel bacteria are present in groundwater within the DNAPL source zone, and the population appears to contain bacterial components necessary to carry out reductive dechlorination.

Received 21 November 2005; revised 1 March 2006; accepted 8 March 2006.
First published online 8 May 2006.

DIGITAL OBJECT IDENTIFIER (DOI)

10.1111/j.1574-6941.2006.00146.x About DOI