Walrycin B is a novel antibacterial compound specifically targeting the essential WalR response regulator. IC50 value: 0.39 ug/ml (MIC for B. subtilis 168); 3.13 ug/ml (MIC for S. aureus N315) Target: bacterial WalR response regulator; Antibacterial Walrycin B is known as an analog of toxoflavin (a phytotoxin from Burkholderia glumae), which has been shown to have a strong MIC for B. subtilis and S. aureus but whose mode of action is not clear. The compound could also interact with WalR to cause bactericidal effects. Walrycins are a new class of potent small molecule compounds that kill bacterial cells by targeting the RR WalR and inhibiting this essential signal transduction pathway. They not only have therapeutic potential but will also prove to be useful reagents for the further study of the WalK/WalR TCS. Walrycin B target WalR and lead to cell death in both B. subtilis and S. aureus.