DEVELOPMENT OF A SENSITIVE CHEMILUMINOMETRIC ASSAY FOR THE DETECTION OF BETA-GALACTOSIDASE IN PERMEABILIZED COLIFORM BACTERIA AND COMPARISON WITH FLUOROMETRY AND COLORIMETRY

We developed a chemiluminometric assay of beta-galactosidase in colifo rm bacteria, using a phenylgalactose-substituted 1,2-dioxetane derivat ive as a substrate. Permeabilization of cells is required to ensure th e efficient cellular uptake of this compound. By this method, one coli form seeded in 100 mi of sterile water can be detected after a 6- to 9 -h propagation phase followed by a 45-min enzyme assay in the presence of polymyxin B. Compared with fluorometry and colorimetry, chemilumin ometry afforded 4- and 1,000-fold increases in sensitivity and 1- and 6-h increases in the speed of detection, respectively.