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Bioluminescent Bioreporter Integrated Circuit
Many types of lux transcriptional gene fusions have been used to develop light-
emitting bioreporter bacterial strains to sense the presence, bioavailability, and
biodegradation of pollutants including toluene [3] and isopropylbenzene [55].
Analogous genetic approaches have also been reported for inducible heavy-
metal detoxification and heavy-metal-resistance systems (including mercury
[54]), and for response to heat shock [61] and oxidative stress [7]. In addition,
genetically engineered Gram-positive bioreporters have been used to examine
the efficacy of antimicrobial agents (decreased light equates to greater effi-
cacy) [2, 15]. Eukaryotic bioreporters have also been generated to detect toxic
compounds [1, 27], oxygen [23], ultraviolet light [9], and estrogenic and anti-
estrogenic compounds [52]. Microorganisms with these lux gene fusions have
been used extensively in biosensor devices [16, 20] by combining the cells with
an appropriate light transducer.
Implicit in the use of a bioreporter strain for a biosensor is the assumption
that the bioluminescent signal generated is directly related to the concentration
of the target substance, most desirably in a selective and quantitative manner.
In general, the lux reporter genes are placed under the regulatory control of in-
ducible operons maintained in native plasmids, in plasmids with a broad range
of hosts, or chromosomally integrated into the host strain. In these genetic
systems, the target analyte or its degradation products act as the inducer of
the bioluminescence genes and are responsible for selectivity and the result-
ing response. For example, Pseudomonas fluorescens HK44 is a bioreporter
that produces light in the presence of naphthalene. This strain has two genetic
operons positively regulated by NahR, a LysR-type protein (Figure 8.1).
Figure 8.1 The two genetic operons positively regulated by NahR in the bioreporter
Pseudomonas fluorenscens HK44 that produced light in the presence of naphtha-
lene. The operon on the right contains the lux bioluminescence genes, while the other
operon contains the genes responsible for the degradation of naphthalene to salicylate.
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