A portable toxicity biosensor using freeze-dried recombinant bioluminescent bacteria.

A portable biosensor has been developed to meet the demands of field toxicity analysis. This biosensor consists of three parts, a freeze-dried biosensing strain within a vial, a small light-proof test chamber, and an optic-fiber connected between the sample chamber and a luminometer. Various genetically engineered bioluminescent bacteria were freeze-dried to measure different types of toxicity based upon their modes of action. GC2 (lac::luxCDABE), a constitutively bioluminescent strain, was used to monitor the general toxicity of samples through a decrease in its bioluminescence, while specific toxicity was detected through the use of strains such as DPD2540 (fabA::luxCDABE), TV1061 (grpE::luxCDABE), DPD2794 (recA::luxCDABE), and DPD2511 (katG::luxCDABE). These inducible strains show an increase in bioluminescence under specific stressful conditions, i.e. membrane-, protein-, DNA-, and oxidative-stress, respectively. The toxicity of a sample could be detected by measuring the bioluminescence 30 min after addition to the freeze-dried strains. In an attempt to enhance the sensitivity of the freeze-dried cells, glucose and Tween 80 were tested as additives. It was found that the addition of glucose had a negative effect on the viability of the freeze-dried cells, while samples having Tween 80 showed an increase in their viability. On the other hand, the addition of either Tween 80 or glucose decreased the final bioluminescent response of DPD2540 in response to 4-chlorophenol. Using these strains, many different chemicals were tested and characterized. This portable biosensor, with a very simple protocol, can be used for field sample analysis and the monitoring of various water systems on-site.