Environmental Engineering Reference
In-Depth Information
Probing for functional genes
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Lane order:
GW14
GW15
GW16
GW17
GW18
P16
P17
P23
P38
F1
Br XIII
Br XX
16 S Sequences (890 bp)
Toluene
Dioxygenase
Tod
(521 bp)
Benzene Dioxygenase
Bed
(520 bp)
Figure 12.2.
Molecular probes for functional genes such as toluene dioxygenase (Tod)
and benzene dioxygenase (Bed) which are critical to the bioremediation of BTEX
contaminated sites (mainly by aerobic bacteria) can now be included as part of a routine
screen to assess the potential of an environment sample/site to degrade target
contaminants (Brockman 1995). For contaminated soils, DNA and RNA can be readily
extracted and probed for the above catabolic genes. Aquifer material is more difficult
to obtain and groundwater contains very low population densities of microbial
degraders. A useful approach is to lower inert, high surface area 'tokens' into boreholes
so that they become colonised by representative degraders. DNA/RNA can then be
extracted readily from the tokens and potential contaminant degrader activity of
aquifers assessed.
will be degraded by the microbes possessing these genes at the site. More direct
evidence for assessing this likelihood comes from the mineralisation of
14
C labelled contaminants. The latter are usually added as spikes to soil, sediment
or groundwater. The resulting
14
CO
2
is trapped and the
14
C counted to determine
the fraction of the contaminant pool degraded (Reid et al.
2001
).
Assessment/remediation of two contaminated site case studies is presented to
exemplify applications of the above techniques to characterise microbial ecology
and to demonstrate large/field-scale successes where exploiting an understand-
ing of microbial ecology has enabled effective bioremediation to an environ-
mentally relevant and acceptable endpoint. This heralds an encouraging future
for more sustainable approaches to managing industrially contaminated land.
Case study 1
The first case study involves a substantial (8.5 ha) contaminated petrochemical
plant in the Rhinelands of Germany (
Fig. 12.3
). The site had been a paint
