Environmental Engineering Reference
In-Depth Information
Biosensors
Analyte
Biological
element
Micro-organisms
Transducer
Optical
Microprocessor
Signal display
Figure 12.1.
Microbial biosensors represent the biological element that, when exposed
to an analyte (a contaminated soil sample or soil extract), provide a diagnostic signal via
an appropriate transducer (in the case of light emitting biosensors, this transducer is
optical). In the case of biosensors constructed for diagnosis of contamination, the
diagnostic signal may reflect the general toxicity of site contamination or the
bioavailable fraction of a specific contaminant or group of contaminants.
of biosensors (
Fig. 12.1
) to assess the extent and impact of contamination, to
support the bioremediation process and to establish restoration of soil health.
The support of bioremediation using biosensors involves both determining
the potential for bioremediation and identifying possible constraints to bio-
remediation so that they can be alleviated through engineered interventions,
as part of bioremediative management support. In particular, lux-marked bac-
terial biosensors, expressing bioluminescence reporter genes either under the
control of a strong, general, constitutive cell promoter (in the case of toxicity
biosensors) or under the control of a contaminant catabolic or resistance
promoter (in the case of contaminant specific biosensors), have proved
extremely useful in this regard. This is because their inherent flexibility, in
terms of host selection and construction, offers strong environmental rele-
vance and both the ability to screen for overall toxicity (due to contaminants
or some other soil factor) or for the availability of a specific site contaminant.
A key series of degradation assessment methods for supporting microbially
driven remediation (bioremediation) of target contaminants includes deter-
mination of the presence of key catabolic genes (
Fig. 12.2
) and mineralisation
of
14
C labelled contaminants.
Although the identificationof key catabolic genes for contaminant degradation
provides useful information, it does not necessarily mean that the contaminants
