After decades of successful treatment of bacterial infections with antibiotics, formerly treatable bacteria have developed drug resistance and consequently pose a major threat to public health. To address the urgent need for effective antibacterial drugs we will develop a streamlined chemical-biology platform that facilitates the consolidated identification and structural elucidation of natural products together with their dedicated cellular targets. This innovative concept overcomes several limitations of classical drug discovery processes by a chemical strategy that focuses on a directed isolation, enrichment and identification procedure for certain privileged natural product subclasses. This proposal consists of four specific aims: 1) synthesizing enzyme active site mimetics that capture protein reactive natural products out of complex natural sources, 2) designing natural product based probes to identify their cellular targets by a method called activity based protein profiling , 3) developing a traceless photocrosslinking strategy for the target identification of selected non-reactive natural products, and 4) application of all probes to identify novel enzyme activities linked to viability, resistance and pathogenesis. Moreover, the compounds will be used to monitor the infection process during invasion into eukaryotic cells and will reveal host specific targets that promote and support bacterial pathogenesis. Inhibition of these targets is a novel and so far neglected approach in the treatment of infectious diseases. We anticipate that these studies will provide a powerful pharmacological platform for the development of potent natural product derived antibacterial agents directed toward novel therapeutic targets.