Biomedical Engineering Reference
In-Depth Information
This broader examination of both the MBT and chemical parameters will provide a
more complete interpretation of site data, and increase the likelihood of achieving remedial
objectives.
6.9 FUTURE RESEARCH NEEDS
Design and performance monitoring of bioaugmentation systems requires analysis of the
presence, abundance, activity and spatial and temporal dynamics of process-specific biomar-
kers such as Dhc and VC reductase targets. The tools of molecular biology, particularly qPCR,
have allowed researchers to overcome the limitations imposed by the difficulties in culturing
Dhc from environmental samples, and have greatly improved the ability to evaluate the need
for bioaugmentation at specific sites, and to monitor the performance of sites after biostimula-
tion or bioaugmentation.
To further advance groundwater monitoring, additional process-specific biomarkers must
be identified. In the case of chlorinated ethenes, Dhc bacteria have been identified as key
players to achieve complete reductive dechlorination to nontoxic end products, and currently
several reductive dechlorinase genes have been identified. However, other bacteria, such as
Geobacter, Dehalobacter, Desulfitobacterium and Desulfuromonas species, may play just as
important a role in remediating chlorinated solvent-impacted sites. For example, a study by
Amos et al. ( 2009 ) identified genes in a Geobacter strain that are implicated in the reductive
dechlorination of chlorinated ethenes, but their potential value as MBT targets in the field is not
well understood.
To reduce analysis costs, even with a broader suite of biomarker targets, a tiered approach
to evaluating microbial communities is recommended. Initial characterization of a site should
focus on a wider range of available Dhc biomarkers. These results then can be used to tailor
qPCR assays that only enumerate biomarkers that are informative for a given site. Groundwa-
ter analysis for monitoring microbial processes in the subsurface requires that the target
microbes are, at least partly, planktonic. The factors controlling the switch from sessile (e.g.,
biofilm growth) to planktonic lifestyle are largely unknown for most subsurface bacteria, which
confounds quantitative assessment of groundwater samples and data interpretation.
ACKNOWLEDGEMENT
The authors thank Mark Davidson of Geosyntec Consultants for a thoughtful review of the
manuscript.
REFERENCES
Alvarez-Cohen L. 2007. Application of microarrays and qPCR to identify phylogenetic
and fundamental biomarkers diagnostic of microbial communities that biodegrade chlori-
nated solvents to ethene. SERDP Project ER-1587 Fact Sheet. http://www.serdp-estcp.org/
Program-Areas/Environmental-Restoration/Contaminated-Groundwater/Monitoring/ER-
1587/ER-1587 . Accessed June 12, 2012.
Amos BK, Suchomel EJ, Pennell KD, L¨ffler FE. 2009. Spatial and temporal distributions of
Geobacter lovleyi and Dehalococcoides spp. during bioenhanced PCE-DNAPL dissolution.
Environ Sci Technol 43:1977-1985.
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