Effects of legacy nuclear waste on the compositional diversity and distributions of sulfate-reducing bacteria in a terrestrial subsurface aquifer

Abstract

The impact of legacy nuclear waste on the compositional diversity and distribution of sulfate-reducing bacteria in a heavily contaminated subsurface aquifer was examined. dsrAB clone libraries were constructed and restriction fragment length polymorphism (RFLP) analysis used to evaluate genetic variation between sampling wells. Principal component analysis identified nickel, nitrate, technetium, and organic carbon as the primary variables contributing to well-to-well geochemical variability, although comparative sequence analysis showed the sulfate-reducing bacteria community structure to be consistent throughout contaminated and uncontaminated regions of the aquifer. Only 3% of recovered dsrAB gene sequences showed apparent membership to the Deltaproteobacteria. The remainder of recovered sequences may represent novel, deep-branching lineages that, to our knowledge, do not presently contain any cultivated members; although corresponding phylotypes have recently been reported from several different marine ecosystems. These findings imply resiliency and adaptability of sulfate-reducing bacteria to extremes in environmental conditions, although the possibility for horizontal transfer of dsrAB is also discussed.

Impact of elevated nitrate on sulfate-reducing bacteria: a comparative Study of Desulfovibrio vulgaris

“…Nitrate inhibition of metal-reducing microbial populations, such as the SRB, hinders bioremediation efforts exploiting these microbial biocatalysts (Abdelouas et al, 1998;Finneran et al, 2002;Istok et al, 2004;Nyman et al, 2006). However, the persistence of sulfate-reducing bacteria at contaminated sites with high nitrate levels suggested the presence of potential resistance mechanisms (Gu et al, 2005;Bagwell et al, 2006;Fields et al, 2006), which were explored in this study using physiological and genomics approaches. Growth inhibition by nitrate in the form of osmotic stress was demonstrated by the up-regulation of the glycine/betaine transporter genes and the relief of nitrate inhibition by osmoprotectant (Figure 2).…”

“…(Lovley et al, 1993b;Lloyd et al, 1999;Payne et al, 2002), which are the model SRBs most extensively studied for their bioremediation capacity. More importantly, SRB populations are also found to be significant members of microbial communities involved in such metal reduction and are ubiquitous even in extreme environments (Chang et al, 2001;Gillan et al, 2005;Bagwell et al, 2006;Fields et al, 2006). Therefore, stimulation of SRB activities has been considered as a useful approach for the immobilization of heavy metals and radionuclides (Landa, 2005;Lloyd and Renshaw, 2005).…”

Functional Gene Array-Based Analysis of Microbial Community Structure in Groundwaters with a Gradient of Contaminant Levels

“…2b). Well TPB-16 has a moderate contaminant load, and sulfate concentration (116.1 mg -1 l) and is located near a zerovalent iron reactive barrier that was installed for the purpose of passively remediating the soil (Bagwell, 2006). Increased sulfate reduction has been observed close to the barrier at this site, and in other Fe 0 barriers (Gu, 2002;Gu, 1999;Phillips, 2002).…”

“…The contaminants alter local bacterial populations by exerting selective pressure (Akob et al, 2007), but leave other populations intact (Bagwell et al, 2006). Many studies of this site have used culturing techniques (M. Fields et al, 2005;Spain et al 2007) and molecular biomarker analysis (Palumbo et al, 2004;Bagwell et al, 2006;Yan et al, 2003;Akob et al, 2007, Spain et al 2007 to examine the bacterial diversity and functional capabilities of bacteria present in the area, but none of these studies have been able to simultaneously examine the 4 diversity of multiple functional genes. The objective of this study is to examine the bacterial community structure in wells of varying contamination and to determine which contaminants have the greatest effects on bacterial diversity.…”

Diversity of bacterial communities in acid mine drainage from the Shen-bu copper mine, Gansu province, China

“…Principal component analysis (PCA) was performed using the SYSTAT statistical computing package (version 13.0; SPSS, Inc., Chicago, IL) and consulting protocols described by previous works (Palumbo et al 2004;Bagwell et al 2006) for each sampling site. PCA provides a means to separate and group sampling sites based on their complex biogeochemical profiles and community patterns, since it simultaneously considers many correlated variables and then identifies the lowest number to accurately represent the structure of the data (Sharma, 1995).…”