Screen for Inducers of Autolysis in Bacillus subtilis

We describe a primary high-throughput screen that uses the reporter strain Bacillus subtilis BAU-102 to identify antibiotics that induce autolysis. The screen measures autolysis in terms of the incipient release of recombinant Escherichia coli beta-galactosidase (beta-Gal) from the periplasmic space of B. subtilis owing to a loss of integrity of the cell wall. In a model screen, beta-Gal release values for 79 members of a library consisting of antibiotics and related compounds were collected, sorted, and plotted as a function of rank. Inducers of autolysis, which included compounds that inhibit cell wall synthesis and those that do not, were readily differentiated from other members of the library on the basis of their elevated beta-galactosidase release responses. The results of the BAU-102 model screen called attention to the antibacterial activity of drugs normally used in other applications, describable as repurposed. Thus, the screen independently identified the potential antibacterial properties of the antifungal drug miconazole and of the antileishmaniasis drug miltefosine. Daptomycin-induced release of beta-Gal was also detected and occurred in a Ca(2+)-dependent manner.