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One of the operons contains the lux bioluminescence genes and the other
genes responsible for the degradation of naphthalene to salicylate, the metabolic
intermediate of naphthalene degradation. Both operons are induced when sali-
cylate interacts with the regulatory protein NahR. Therefore, exposure of HK44
to either naphthalene or salicylate results in increased gene expression and in-
creased bioluminescence. Initial studies in continuous cultures of P. fluorescens
HK44 have demonstrated that the magnitude of the bioluminescence response
correlated with the aqueous-phase concentration of naphthalene under pulsed-
perturbation conditions [35]. Using growing cell cultures, a linear relationship
to bioluminescence was found for both naphthalene and salicylate (correlation
coefficient, r 2 , of .990 for naphthalene and 0.991 for salicylate) over a con-
centration range of two orders of magnitude. Reproducible bioluminescence
was observed not only in aqueous naphthalene samples but also in soil-slurry
samples spiked with naphthalene, complex soil leachates and the water-soluble,
components of jet fuel [30].
Combining these bioreporters with an integrated microluminometer forms
a BBIC (Figure 8.2). We have implemented our microluminometer in a com-
plementary metal oxide semiconductor (CMOS) technology.
This CMOS IC, shown in Figure 8.3, is described in detail elsewhere [57]
and will not be presented further here because the details of the circuit design
are not central to the incorporation of cells into microscale devices. However,
one aspect of the BBIC that is of particular interest for the realization of highly
integrated whole-cell devices is the packaging of the cells. We present this in
some detail below.
Figure 8.2 Bioluminescent bioreporter integrated circuits (BBICs). The integrated
circuit (IC) is packaged in a 40-pin chip carrier and the bioreporters are positioned
directly above the IC. All of the light for this photograph is provided by the biolumi-
nescence (40-minute exposure).
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