and Antibacterial Activity of Serratamid, a Novel Peptide-Polyketide Antibiotic Isolated from C1, against Phytopathogenic Bacteria.

A new hybrid non-ribosomal peptide-polyketide antibiotic (serratamid) for phytoprotection was isolated from the ethyl acetate layer of tryptic soy agar culture of the soil bacterium C1 through bioassay-guided fractionation. Its chemical structure was elucidated using instrumental analyses, such as mass and nuclear magnetic resonance spectrometry. Serratamid showed antibacterial activity against 15 phytopathogenic bacteria, with minimum inhibitory concentration (MIC) values ranging from 0.244 to 31.25 μg/mL. , it displayed strong antibacterial activity against and four spp., with MIC values (0.244-0.488 μg/mL) superior to those of streptomycin sulfate, oxolinic acid, and oxytetracycline. Further, serratamid and the ethyl acetate layer of C1 effectively reduced bacterial wilt caused by on tomato seedlings and fire blight caused by on apple fruits in a dose-dependent manner. These results suggest that serratamid is a promising candidate as a potent bactericide for controlling bacterial diseases.