Identification of virulence factors mediating phagosomal escape of Staphylococcus aureus by transposon insertion site deep sequencing
Final Report Abstract
In this study we performed a screen for S. aureus gene products involved in phagosomal escape of the pathogen. We identified several candidates, of which we characterized mutants within a non-ribosomal peptide synthase (NRPS). We provide evidence that the S. aureus NRPS and its peptide product, phevalin, enhance S. aureus phagosomal escape thereby contributing to epithelial and immune cell death. Bacterial mutants in the associated genes are significantly attenuated in vitro and in vivo. Attenuation of virulence is readily recovered by genetic complementation as well as addition of synthetic phevalin. Furthermore, we identified a role for the NRPS in S. aureus induced pneumonia, during which S. aureus encounters phagocytic cells, such as alveolar macrophages and immigrating neutrophils. In an unbiased transposon mutant pool screen, a mutant in the NRPS was attenuated in virulence being recovered in significantly reduced numbers from mouse lungs when compared to the inoculum used. Our study further suggests that phevalin targets a host cell protein, but does not act as a calpain inhibitor during phagosomal escape. S. aureus thus uses a non-ribosomal peptide assembly line to form a cyclic dipeptide, which governs virulence of S. aureus on the host level. This renders the host target of phevalin a potential target for the development of antiinfectives, since S. aureus would not be able to develop resistance to a target encoded in the host genome. Our findings further support that S. aureus uses small molecules, which are usually used for interbacterial communication, to communicate with and influence its host.
Publications
- 2014. Cytoplasmic replication of Staphylococcus aureus upon phagosomal escape triggered by phenol-soluble modulin alpha. Cell Microbiol 16:451-465
Grosz, M., J. Kolter, K. Paprotka, A. C. Winkler, D. Schafer, S. S. Chatterjee, T. Geiger, C. Wolz, K. Ohlsen, M. Otto, T. Rudel, B. Sinha, and M. Fraunholz
(See online at https://doi.org/10.1111/cmi.12233) - Influence of Sae-regulated and Agr-regulated factors on the escape of Staphylococcus aureus from human macrophages. Cell Microbiol. 18,8, August 2016, Pages 1172-1183
Münzenmayer, L., T. Geiger, E. Daiber, B. Schulte, S. E. Autenrieth, M. Fraunholz, and C. Wolz
(See online at https://doi.org/10.1111/cmi.12577) - Naturally mutations in a Staphylococcus aureus virulence regulator attenuate cytotoxicity but permit bacteremia and abscess formation. PNAS May 31, 2016 113 (22) E3101-E3110
Das S., Lindemann C., Young B., Muller J., Österreich B., Ternette N., … and Martin Fraunholz
(See online at https://doi.org/10.1073/pnas.1520255113) - “Staphylococcus aureus exploits a non-ribosomal cyclic dipeptide to modulate survival within Epithelial Cells and Phagocytes". PLoS Pathog 12(9): e1005857, 2016
Sebastian Blättner, Sudip Das, Kerstin Paprotka, Ursula Eilers, Markus Krischke, Dorothee Kretschmer, Christian W. Remmele, Marcus Dittrich, Tobias Mueller, Christina Schuelein-Voelk, Tobias Hertlein, Martin J. Mueller, Bruno Huettel, Richard Reinhardt, K
(See online at https://doi.org/10.1371/journal.ppat.1005857)
