Matti Korpela

Detection of tetracyclines with luminescent bacterial strains.

The performance of two bioluminescent Escherichia coli K-12 strains for the specific detection of the tetracycline family of antimicrobial agents was compared, and the analytical applicability of one of the strains was preliminarily evaluated. One sensor plasmid contained the bacterial luciferase operon of Photorhabdus luminescens under the control of the tetracycline-responsive element from transposon Tn10 (15). An analogous plasmid construction with firefly (Photinus pyralis) luciferase reporter gene was constructed, and these two divergent tetracycline-inducible light-emitting systems were compared for their suitability for the qualitative detection of tetracyclines. Both sensor strains behaved in a similar manner kinetically, and the most sensitive tetracycline response for both sensor strains was achieved in 90-120 min by performing the assay at 37 degrees C. The sensor strain containing the bacterial luciferase operon responded slightly more sensitively to different tetracyclines than the strain containing firefly luciferase gene. The sensor bacteria retained their inducibility in lyophilization, and freeze-dried cells detected tetracyclines as sensitively as freshly cultivated sensor cells. The preliminary results from the analysis of tetracycline-spiked pork serum samples indicated that these sensor bacteria could be used to screen veterinary samples for tetracycline residues in real-time.

Stable-light producingEscherichia coli

SummaryStable light production inEscherichia coli is achieved by cloning the genes encoding bacterial luciferase fromVibrio harveyi. To gain advantage of sensitive detection of light we transferred the genes under the control of a regulatable promoter system and searched for growth and buffer conditions where bacteria emitted stable light. Based on our findings an automated biosensor system can be developed to monitor the effects of biologically active compounds against stable-light producing bacteria.