Identifying the mechanism of action of Tartrolon E, a broad-spectrum anti-apicomplexan compound

Primary Author: Gregory Bowden

Faculty Sponsor: Roberta O’Connor


Primary College/Unit: College of Veterinary Medicine

Category: Medical and Life Sciences

Campus: Pullman





The apicomplexan parasite Cryptosporidium is the cause of the severe diarrheal disease, cryptosporidiosis. Cryptosporidiosis is one of the most important diseases of children, immunocompromised individuals, and young ruminant livestock. Currently, there is no treatment for neonatal ruminants, and the only approved treatment for immunocompromised individuals is ineffective; a new treatment is needed.  Recently we identified Tartrolon E (TrtE), a compound from shipworm symbiotic bacteria, to have broad-spectrum anti-apicomplexan parasite activity, including activity against Cryptosporidium. The purpose of this work was to uncover the mechanism of action of TrtE against apicomplexan parasites by examining gene expression during treatment.


We studied the mechanism of action of TrtE using the model apicomplexan parasite Toxoplasma gondii. Changes in gene expression during treatment were determined by RNA-sequencing and verified by RT-qPCR. We investigated the potential function of the responsive gene using bioinformatics and immunofluorescence assays. To examine the effect of this gene on parasite susceptibility to TrtE, we deleted the gene using CRISPR/Cas9.


RNA-sequencing data revealed that T. gondii responds to TrtE treatment by upregulating TGME49_272370 (TERG) in a rapid dose-dependent manner. TERG encodes for an unknown protein with multiple predicted transmembrane domains. Immunofluorescence assays located the TERG protein to punctate areas throughout the cytoplasm. The deletion of TERG resulted in a 22% increase in parasite susceptibility to TrtE. In uncovering the mechanism by which TrtE inhibits T. gondii parasites, we may identify a shared pathway critical to apicomplexan parasite survival and advance the search for a new treatment for cryptosporidiosis.