Whole Cell Luminescence-Based\nScreen for Inhibitors\nof the Bacterial Sec Machinery

There is a pressing need for new antibiotics to combat\nrising resistance\nto those already in use. The bacterial general secretion (Sec) system\nhas long been considered a good target for novel antimicrobials thanks\nto its irreplacable role in maintaining cell envelope integrity, yet\nthe lack of a robust, high-throughput method to screen for Sec inhibition\nhas so far hampered efforts to realize this potential. Here, we have\nadapted our recently developed <i>in vitro</i> assay for\nSec activitybased on the split NanoLuc luciferaseto\nwork at scale and in living cells. A simple counterscreen allows compounds\nthat specifically target Sec to be distinguished from those with other\neffects on cellular function. As proof of principle, we have applied\nthis assay to a library of 5000 compounds and identified a handful\nof moderately effective <i>in vivo</i> inhibitors of Sec.\nAlthough these hits are unlikely to be potent enough to use as a basis\nfor drug development, they demonstrate the efficacy of the screen.\nWe therefore anticipate that the methods presented here will be scalable\nto larger compound libraries, in the ultimate quest for Sec inhibitors\nwith clinically relevant properties.