A polyether antibiotic, ecteinamycin (1), was isolated from a marine Actinomadura sp., cultivated from the ascidian Ecteinascidia turbinata. 13C enrichment, high resolution NMR spectroscopy, and molecular modeling enabled elucidation of the structure of 1, which was validated on the basis of comparisons with its recently reported crystal structure. Importantly, ecteinamycin demonstrated potent activity against the toxigenic strain of Clostridium difficile NAP1/B1/027 (MIC = 59 ng/μL), as well as other toxigenic and nontoxigenic C. difficile isolates both in vitro and in vivo. Additionally, chemical genomics studies using Escherichia coli barcoded deletion mutants led to the identification of sensitive mutants such as trkA and kdpD involved in potassium cation transport and homeostasis supporting a mechanistic proposal that ecteinamycin acts as an ionophore antibiotic. This is the first antibacterial agent whose mechanism of action has been studied using E. coli chemical genomics. On the basis of these data, we propose ecteinamycin as an ionophore antibiotic that causes C. difficile detoxification and cell death via potassium transport dysregulation.
Bibliographical noteFunding Information:
Additional equipment was purchased with funds from the University of Wisconsin, the NIH (RR02781, RR08438), the NSF (DMB-8415048, OIA-9977486, BIR-9214394), and the USDA. We would like to thank G. Ananiev from the UWCCC Small Molecule Screening Facility (SMSF) for performing the hemolysis screening. We also would like to thank D. Demaria for assistance with sample collection.
This work was supported by funding from the University of Wisconsin-Madison School of Pharmacy and from the University of Wisconsin Institute for Clinical and Translational Research funded through NIH/NCATS UL1TR000427. This work was also funded by the NIH, NIGMS Grant R01GM104192 (T.S.B.). J.S.P. was funded by the DOE Great Lakes Bioenergy Research Center (DOE BER Office of Science DE-FC02-07ER64494). C.L.M. was supported by grants from the NIH (1R01HG005084-01A1, 1R01GM104975-01, R01HG005853), a grant from the National Science Foundation (DBI 0953881), and by the CIFAR Genetic Networks Program. For H. Mori: JSPS Kakenhi 25250028, 16H02485 and MEXT Kakenhi 25108716, Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan. We thank the Analytical Instrumentation Center at the University of Wisconsin-Madison for the facilities to acquire spectroscopic data. This study made use of the National Magnetic Resonance Facility at Madison, which is supported by NIH grant P41GM103399.
© 2017 American Chemical Society.