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Updated: Jun 29, 2025
Super-Resolution Imaging of Bacterial Secreted Proteins Using Genetic Code Expansion
Published on: February 10, 2023
PIX is an N-terminal delivery domain that defines a class of polymorphic T6SS effectors in Enterobacterales
Andrea Carobbi1, Ksenia Leo1, Simone Di Nepi2
1Department of Clinical Microbiology and Immunology, School of Medicine, Faculty of Medical and Health Sciences, Tel Aviv University, Tel Aviv, Israel; School of Plant Sciences and Food Security, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
Abstract:
The type VI secretion system (T6SS), a widespread protein delivery apparatus, plays a role in bacterial competition by delivering toxic effectors into neighboring cells. Identifying new T6SS effectors and deciphering the mechanism that governs their secretion remain major challenges. Here, we report two orphan antibacterial T6SS effectors in the pathogen Pantoea agglomerans (Pa). These effectors share an N-terminal domain, Pantoea type six (PIX), that defines a widespread class of polymorphic T6SS effectors in Enterobacterales. We show that the PIX domain is necessary and sufficient for T6SS-mediated effector secretion and that PIX binds to a specialized Pa VgrG protein outside its C-terminal toxic domain. Our findings underline the importance of identifying and characterizing delivery domains in polymorphic toxin classes as a tool to reveal effectors and shed light on effector delivery mechanisms.
Insights
Researchers identified new bacterial toxins delivered by the type VI secretion system (T6SS) in Pantoea agglomerans. The PIX domain is crucial for delivering these toxins, advancing our understanding of bacterial competition mechanisms.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- The type VI secretion system (T6SS) is vital for bacterial competition, delivering toxic effectors to neighboring cells.
- Identifying novel T6SS effectors and their secretion mechanisms is crucial for understanding bacterial interactions.
Purpose of the Study:
- To identify and characterize new antibacterial T6SS effectors in Pantoea agglomerans (Pa).
- To elucidate the secretion mechanism of these novel effectors, focusing on the role of the PIX domain.
Main Methods:
- Genetic analysis of Pantoea agglomerans.
- Identification and characterization of novel T6SS effectors.
- Protein-protein interaction studies to investigate effector-host interactions.
Main Results:
- Two orphan antibacterial T6SS effectors were identified in Pa.
- A conserved N-terminal domain, Pantoea type six (PIX), was identified and shown to be essential for T6SS-mediated secretion.
- The PIX domain mediates effector secretion by binding to a specialized Pa VgrG protein.
Conclusions:
- The PIX domain is a key determinant for T6SS effector secretion in Enterobacterales.
- Characterizing delivery domains is essential for discovering new effectors and understanding T6SS mechanisms.
- This study provides insights into the polymorphic nature of T6SS effectors and their delivery strategies.
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