A BACTERIAL TOXICITY ASSAY PERFORMED WITH MICROPLATES, MICROLUMINOMETRY AND MICROTOX(R) REAGENT

We have developed a procedure for undertaking a Microtox(R)-based test by coupling microplate and microluminometric technologies. Sample dil utions are prepared in a 96-well polystyrene microplate kept at 15 deg rees C, while the Microtox reagent and diluent are placed in an opaque , microluminometry-compatible 96-well microplate also kept at 15 degre es C. Exposure begins when sample aliquots are brought into contact wi th bacterial reagents in the opaque Inicroplate. After specific exposu re times (5, 15, 30 and 60 min), bacterial luminescence is rapidly mea sured by placing the opaque microplate in a microluminometer Reproduci bility of the procedure, as well as general agreement of EC50 end-poin t values with published reports, is demonstrated herein after toxicity trials with six metals (Ni2+, Cd2+, Zn2+, Pb2+, Cu2+ and Cr6+). Resul ts suggest that a 60-min exposure time may have value in gel ting more ''sensitivity mileage'' out of this Microtox-based assay. This microp late procedure possesses attractive features that augment sample throu ghout and information output. Further refinement and validation studie s are ongoing in our laboratories.