High-throughput elicitor screen to induce the sur cluster. (A) Relative expression of a neutral site reporter, attB::Psur-eGFPx3 (top), or targeted sur reporter, surE::eGFPx3 (bottom), as a function of exogenously supplied small molecules. Each bar represents the response to a specific molecule from a library of 502 natural products, acquired as a single replicate. Plus signs denote the positive control, attB::PermE-eGFPx3. Minus signs denote the negative controls, attB::Psur-eGFPx3 (top) or surE::eGFPx3 (bottom) in the absence of any metabolites. The expression has been normalized to the positive control. Compounds that gave the top eight hits are marked. (B) Structures of the top six elicitors, observed in both HiTES assays, shown in panel A.