Analytica Chimica Acta 422 (2000) 121–130 Fiber optic detection of in situ lux reporter gene activity in porous media: system design and performance Irfan Yolcubal a , Joseph J. Piatt b , Shelley A. Pierce b , Mark L. Brusseau a,b , Raina M. Maier b,∗ a Hydrology and Water Resources, University of Arizona, 429 Shantz, Tucson, AZ 85721, USA b Department of Soil, Water and Environmental Science, University of Arizona, 429 Shantz, Tucson, AZ 85721, USA Received 17 February 2000; received in revised form 6 July 2000; accepted 12 July 2000 Abstract A luminescence detection system is described that couples a genetically engineered bioluminescent reporter organism and fiber optic technology for monitoring in situ reporter gene activity in porous media under dynamic conditions. The reporter bacterium used was Pseudomonas putida RB1353, which carries plasmids NAH7 and pUTK9 that encode genes for salicylate degradation (nah) and luminescence (lux) that are regulated by the same promoter. The system can be used to examine the relationship between microbial activity and the resultant impact on biodegradation and transport of salicylate in porous media. Several batch and column experiments were conducted to analyze the performance of the fiber optic detection system. Batch studies showed that the fiber optic response in liquid cultures was linearly correlated to a calibrated system response using a liquid scintillation counter in the single photon counting mode. In column studies, it was demonstrated that decreases in salicylate and dissolved oxygen concentrations associated with biodegradation were correlated with an increase in luminescence response. The maximum luminescence given off by the reporter organism was linearly related to salicylate concentration. These results indicate that the fiber optic system can be used to monitor microbial activity under dynamic conditions. This system allows rapid, real-time, and non-destructive measurements of luminescence from a specific lux reporter microbial population in porous media. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Bioluminescence; Reporter organism; Biosensor; Biodegradation 1. Introduction One of the most promising remediation techniques currently available for soil and ground water is in situ bioremediation, including passive or intrinsic ap- proaches, as well as active methods, wherein the pro- cess is stimulated by an addition of nutrients, electron donors, or micro-organisms [1]. The bioavailability ∗ Corresponding author. Tel.: +1-520-621-7231; fax: +1-520-621-1647. E-mail address: rmaier@ag.arizona.edu (R.M. Maier). and biodegradation of organic contaminants in subsur- face systems is affected by both physicochemical and biological processes that are kinetically constrained (e.g. solubility/dissolution, sorption/desorption, and enzyme induction). In addition, it is well known that the subsurface is heterogeneous and that this heterogeneity exerts a major impact on both con- taminant bioavailability (e.g. diffusive mass transfer between lower and higher permeability zones) and microbial distribution. In order to understand, pre- dict, and enhance biodegradation processes in het- erogeneous subsurface environments, information is 0003-2670/00/$ – see front matter © 2000 Elsevier Science B.V. All rights reserved. PII:S0003-2670(00)01072-2