Measuring β-Galactosidase Activity in Gram-Positive Bacteria Using a Whole-Cell Assay with MUG as a Fluorescent Reporter

The use of β-galactosidase enzyme as a biomarker has the potential to determine activity levels of the microbiome of a variety of organisms due to its common presence in both eukaryotes and prokaryotes. Completing the assay in a whole-cell format facilitates the monitoring of β-galactosidase activity in its actual cellular environment. This unit describes an optimized fluorescent assay for β-galactosidase that has enough sensitivity to detect the enzymatic activity despite the thick gram-positive bacterial cellular membrane. The use of a smaller fluorometric substrate, namely 4-methylumbelliferyl β-D-galactopyranoside (MUG), has facilitated its penetration into the cells as well as its direct detection without any extra steps. This assay provides an improved technique for measuring a well-studied reporter enzyme and offers new avenues for using β-galactosidase as a biomarker. © 2017 by John Wiley & Sons, Inc.