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

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 x 10(7) 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.

Dehalogenimonas lykanthroporepellens gen. nov., sp. nov., a reductively dehalogenating bacterium isolated from chlorinated solvent-contaminated groundwater

“…These final products are compounds that contribute to the recognizable odour associated with garlic (Laakso et al, 1989;Lawson, 1996). The two strains were isolated from groundwater collected from a waste recovery well at the PetroProcessors of Louisiana, Inc. Superfund Site, near Baton Rouge, LA, USA, an area heavily contaminated with chlorinated solvents (Bowman et al, 2006). Data from the present study show that strains BL-DC-9…”

“…The two strains exhibited reductive dechlorination of 1,2-dichloropropane, a growth-related process, in the pH range 6.0-8.0 but not at pH ¡5.5 or ¢8.5 during a 2-month incubation period (Yan et al, 2009). As the groundwater at the location from which the strains were isolated had a pH of 5.1 (Bowman et al, 2006), the habitat of these strains probably extends to pH levels somewhat lower than determined in the laboratory test conditions employed by Yan et al (2009).…”

“…(He et al, 2003Kube et al, 2005;Sung et al, 2006). There has been intense interest in this group of bacteria because of their ability to reductively dehalogenate a variety of chlorinated compounds that are widespread pollutants of environmental importance (Hendrickson et al, 2002;Bowman et al, 2006). At the time of writing, however, the genus 'Dehalococcoides' has not been formally described.…”

Olsenella umbonata sp. nov., a microaerotolerant anaerobic lactic acid bacterium from the sheep rumen and pig jejunum, and emended descriptions of Olsenella, Olsenella uli and Olsenella profusa

“…Olsenellae are found in the healthy (Ozutsumi et al, 2005;Cho et al, 2006;Hernandez et al, 2008) and acidotic (Tajima et al, 2000) bovine rumen. Moleculargenetic studies have also reported the detection of Olsenella-related clones in the gastrointestinal tracts of humans (Martinez-Medina et al, 2006;Khachatryan et al, 2008;Krogius-Kurikka et al, 2009), pigs (Leser et al, 2002;Tsukahara & Ushida, 2002;Dowd et al, 2008), wallabies (Chhour et al, 2008) and chickens (Lu et al, 2003) and in diverse anaerobic environmental sites (Bowman et al, 2006;Wongtanet et al, 2007;Weiss et al, 2008;Rivière et al, 2009). This indicates that the habitats of the olsenellae generally comprise the oral cavity and gastrointestinal tract of homoeothermic vertebrates and that non-animal habitats also exist.…”

Characterization of the Community Structure of a Dechlorinating Mixed Culture and Comparisons of Gene Expression in Planktonic and Biofloc-Associated “Dehalococcoides” andMethanospirillumSpecies

“…Several studies have looked at dechlorinating microbial communities derived from both enrichment cultures and environmental systems (8,12,17,21,22,28,30,33,43,54,55,64). Several distinct lineages of microorganisms, representing a variety of metabolic capabilities, are commonly found in these consortia, supporting the potential complexity of community dynamics.…”