Bacteria utilize complex type IV secretion systems (T4SSs) to translocate diverse effector proteins or DNA into target cells. Despite the importance of T4SSs in bacterial pathogenesis, the mechanism by which these translocation machineries deliver cargo across the bacterial envelope remains poorly understood, and very few studies have investigated the use of synthetic molecules to disrupt T4SS-mediated transport. Here, we describe two synthetic small molecules (C10 and KSK85) that disrupt T4SS-dependent processes in multiple bacterial pathogens. Helicobacter pylori exploits a pilus appendage associated with the cag T4SS to inject an oncogenic effector protein (CagA) and peptidoglycan into gastric epithelial cells. In H. pylori, KSK85 impedes biogenesis of the pilus appendage associated with the cag T4SS, while C10 disrupts cag T4SS activity without perturbing pilus assembly. In addition to the effects in H. pylori, we demonstrate that these compounds disrupt interbacterial DNA transfer by conjugative T4SSs in Escherichia coli and impede vir T4SS-mediated DNA delivery by Agrobacterium tumefaciens in a plant model of infection. Of note, C10 effectively disarmed dissemination of a derepressed IncF plasmid into a recipient bacterial population, thus demonstrating the potential of these compounds in mitigating the spread of antibiotic resistance determinants driven by conjugation. To our knowledge, this study is the first report of synthetic small molecules that impair delivery of both effector protein and DNA cargos by diverse T4SSs. IMPORTANCE Many human and plant pathogens utilize complex nanomachines called type IV secretion systems (T4SSs) to transport proteins and DNA to target cells. In addition to delivery of harmful effector proteins into target cells, T4SSs can disseminate genetic determinants that confer antibiotic resistance among bacterial populations. In this study, we sought to identify compounds that disrupt T4SS-mediated processes. Using the human gastric pathogen H. pylori as a model system, we identified and characterized two small molecules that prevent transfer of an oncogenic effector protein to host cells. Wediscovered that these small molecules also prevented the spread of antibiotic resistance plasmids in E. coli populations and diminished the transfer of tumor-inducing DNA from the plant pathogen A. tumefaciens to target cells. Thus, these compounds are versatile molecular tools that can be used to study and disarm these important bacterial machines.
|State||Published - Apr 26 2016|
Bibliographical noteFunding Information:
This work, including the efforts of Maria Hadjifrangiskou, was funded by NCATS/NIH (UL1 TR000445 (VR7227)). This work, including the efforts of Joe Chappell, was funded by USDA-NIFA (2010-04025). This work, including the efforts of Timothy L. Cover, was funded by HHS | National Institutes of Health (NIH) (CA116087, AI118932, and AI039657). This work, including the efforts of Carrie Shaffer, was funded by HHS | National Institutes of Health (NIH) (T32 A1007474-19). This work, including the efforts of Timothy L. Cover, was funded by U.S. Department of Veterans Affairs (VA) (2I01BX000627). This work, including the efforts of Jennifer A. Gaddy, was funded by U.S. Department of Veterans Affairs (VA) (1IK2BX001701). This work, including the efforts of Fredrik Almqvist, was funded by Goran Gustafsson Foundation. This work, including the efforts of Fredrik Almqvist, was funded by Knut och Alice Wallenbergs Stiftelse (Knut and Alice Wallenberg Foundation). This work, including the efforts of Fredrik Almqvist, was funded by Svenska Forskningsradet Formas (Swedish Research Council Formas) (621-2010- 4730). This work, including the efforts of K. Syam Krishnan, was funded by Kempestiftelserna (Kempe Foundations).
© 2016 Shaffer et al.
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