Antibacterial mechanism of houttuyfonate homologues against Bacillus subtilis

In this study the effects of houttuyfonate homologues (HOU-Cn) on the surface and shape, the lipid fluidity and the protein conformation, the fatty acid compositions and fatty acid synthase II (FAS II) of B. subtilis were studied to elucidate the antibacterial mechanism of HOU-Cn against Bacillus subtilis. The scanning electronic microscope (SEM) results showed that the glycocalyx on the surface of B. subtilis disappeared and the cell became smaller after being treated with HOU-Cn. During the co-incubation of HOU-Cn and B. subtilis, HOU-Cn was decomposed into alkyl acyl aldehyde and sodium sulfite rapidly. Then alkyl acyl aldehyde was congregated onto cell membrane and inserted into lipid bilayer, further increased the fluidity of membrane and changed the conformation of membrane protein by hydrophobic binding. Subsequently, HOU-Cn inhibited the FAS II activity, and decreased the synthesis of fatty acids, especially increased the percentage of saturated fatty acid. HOU-Cn showed a strong antibacterial activity against G+-bacteria by a multi-target antibacterial mechanism.