Identification of Type VI Secretion Systems Effector Proteins That Contribute to Interbacterial Competition in Dublin.

The Type VI Secretion System (T6SS) is a multiprotein device that has emerged as an important fitness and virulence factor for many Gram-negative bacteria through the injection of effector proteins into prokaryotic or eukaryotic cells a contractile mechanism. While some effector proteins specifically target bacterial or eukaryotic cells, others can target both types of cells (trans-kingdom effectors). In , five T6SS gene clusters have been identified within pathogenicity islands SPI-6, SPI-19, SPI-20, SPI-21, and SPI-22, which are differentially distributed among serotypes. serotype Dublin (. Dublin) is a cattle-adapted pathogen that harbors both T6SS and T6SS. Interestingly, while both systems have been linked to virulence and host colonization in . Dublin, an antibacterial activity has not been detected for T6SS in this serotype. In addition, there is limited information regarding the repertoire of effector proteins encoded within T6SS and T6SS gene clusters in . Dublin. In the present study, we demonstrate that T6SS and T6SS of . Dublin CT_02021853 contribute to interbacterial competition. Bioinformatic and comparative genomic analyses allowed us to identify genes encoding three candidate antibacterial effectors located within SPI-6 and two candidate effectors located within SPI-19. Each antibacterial effector gene is located upstream of a gene encoding a hypothetic immunity protein, thus conforming an effector/immunity (E/I) module. Of note, the genes encoding these effectors and immunity proteins are widely distributed in genomes, suggesting a relevant role in interbacterial competition and virulence. Finally, we demonstrate that E/I modules SED_RS01930/SED_RS01935 (encoded in SPI-6), SED_RS06235/SED_RS06230, and SED_RS06335/SED_RS06340 (both encoded in SPI-19) contribute to interbacterial competition in . Dublin CT_02021853.