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This paper describes a possible application of luminescent Escherichia coli activated by blood serum for high-sensitivity and high-specificity assays of antibiotics in solutions. Antibiotics inhibited luminescence of a genetically engineered E. coli strain; the system sensitivity to some antibiotics grew notably after the cells had been preactivated by blood serum. The highest level of sensitivity (2.8 ؎ 0.6 ng/ml) of luminescent cells was obtained for aminoglycoside antibiotics (gentamicin and streptomycin). It is feasible to create the specific biosensor for antibiotics on the basis of bioluminescent E. coli strains by applying sera containing antibodies against the antibiotic under assay. The presence of antibodies specific for gentamicin in serum affects inhibition of luminescent cells by gentamicin but not inhibition by other antibiotics.

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At 22 degrees C the bioluminescence decay kinetics in the in vitro reaction catalysed by Vibrio harveyi luciferase in the presence of different aldehydes--nonanal, decanal, tridecanal and tetradecanal did not follow the simple exponential pattern and could be fitted to a two-exponential process. One more principal distinction from the first-order kinetics is the dependence of the parameters on aldehyde concentration. The complex bioluminescence decay kinetics are interpreted in terms of a scheme, where bacterial luciferase is able to perform multiple turnovers using different flavin species to produce light. The initial phase of the bioluminescent reaction appears to proceed mainly with fully reduced flavin as the substrate while the final one results from the involvement of flavin semiquinone in the catalytic cycle.