SCREENING SYSTEMS FOR DETECTING INHIBITORS OF CELL-WALL TRANSGLYCOSYLATION IN ENTEROCOCCUS - CELL-WALL TRANSGLYCOSYLATION INHIBITORS IN ENTEROCOCCUS

We devised two screening systems to detect cell wall transglycosylatio n inhibitors. One screen utilizes a mutant of Enterococcus faecalis st rain A256 that is dependent on vancomycin or moenomycin for growth. In the absence of transglycosylation inhibitors the strain fails to grow , while in the presence of inhibitors, cells are rescued. A second scr eening organism E. faecalis strain MDD212 utilizes a translational fus ion of the lacZ gene to the vanH promoter in a derivative of E. faecal is that contains a vancomycin resistance determinant. Induction of bet a-galactosidase occurs when cells are exposed to inhibitors of transgl ycosylation. Our natural products drug source of fungal fermentations was tested with these screens. Several cultures that produced the same family of compounds, called the thielavins, were detected. Thielavin B inhibited the formation of peptidoglycan in an in vitro assay, sugge sting that these screening systems can detect compounds that interfere with cell wall transglycosylation.