A Bioluminescent Whole-Cell Reporter for Detection of 2,4-Dichlorophenoxyacetic Acid and 2,4-Dichlorophenol in Soil

ABSTRACT A bioreporter was made containing atfdRPDII-luxCDABE fusion in a modified mini-Tn5 construct. When it was introduced into the chromosome of Ralstonia eutropha JMP134, the resulting strain, JMP134-32, produced a sensitive bioluminescent response to 2,4-dichlorophenoxyacetic acid (2,4-D) at concentrations of 2.0 μM to 5.0 mM. This response was linear (R 2 = 0.9825) in the range of 2.0 μM to 1.1 × 102 μM. Saturation occurred at higher concentrations, with maximal bioluminescence occurring in the presence of approximately 1.2 mM 2,4-D. A sensitive response was also recorded in the presence of 2,4-dichlorophenol at concentrations below 1.1 × 102μM; however, only a limited bioluminescent response was recorded in the presence of 3-chlorobenzoic acid at concentrations below 1.0 mM. A significant bioluminescent response was also recorded when strain JMP134-32 was incubated with soils containing aged 2,4-D residues.

Light-stimulated and light-inhibited bioluminescence of the euphausiid Meganyctiphanes norvegica (G. O. Sars)

Innocuous physiological stimuli which excite bioluminescence in Meganyctiphanes norvegica are few; one such is exposure to an appropriate light, another is chemical stimulation by 5-hydroxytryptamine. Meganyctiphanes responds to a photoflash, after some tens of seconds delay, with a bioluminescent glow lasting a few minutes. A second flash stimulus applied during this luminescent response rapidly abolishes it for tens of seconds, after which the glow returns again at full strength. Weak light of about the same colour and intensity as the animal’s own luminescence also depresses the flash-excited glow for the whole time the ambient light is present. 5-hydroxytryptamine (5- HT ), added to the sea water in which the animal swims can either excite continual luminescence or set whatever physiological controls exist into some hyper-sensitive state so that Meganyctiphanes becomes much more responsive to optical stimulation. The delay of onset, duration, amplitude and time course of flash-excited luminescence have been determined quantitatively, together with their dependence upon the intensity and spectral composition of the stimulating flash. Some characteristics of the inhibition by flash and by weak continuous light have been recorded, and also the interaction of 5- HT sensitization upon light excitation and inhibition. These optical stimulus-bioluminescent response relationships establish a well-documented excitatory stimulus which can be used to initiate luminescence at will, leaving the animal in its natural physio-chemical environment. The observations provide an experimental basis for judging some hitherto weakly based speculations about the physiological control of bioluminescence in Meganyctiphanes and suggest sensible ways to investigate this in greater detail.