Macrolactin S, a new antibacterial agent with FabG-inhibitory activity from Bacillus sp. AT28.

In the course of screening for FabG inhibitors from microbial sources, a new 24-membered ring lactone named macrolactin S, along with the known compound macrolactin B, has been isolated from the mycelium of liquid fermentation cultures of Bacillus sp. AT28. The structure of macrolactin S was determined on the basis of MS and NMR data. Macrolactin S showed a dose-dependent inhibition of Staphylococcus aureus FabG, not inhibiting S. aureus FabI. Also macrolactin S inhibited the growth of S. aureus, Bacillus subtilis, and Escherichia coli.