The type VI secretion system (T6SS) is deployed by numerous Gram-negative bacteria to deliver toxic effectors into neighbouring cells. The genome of Pantoea agglomerans pv. betae (Pab) phytopathogenic bacteria contains a gene cluster (T6SS1) predicted to encode a complete T6SS. Using secretion and competition assays, we found that T6SS1 in Pab is a functional antibacterial system that allows this pathogen to outcompete rival plant-associated bacteria found in its natural environment. Computational analysis of the T6SS1 gene cluster revealed that antibacterial effector and immunity proteins are encoded within three genomic islands that also harbour arrays of orphan immunity genes or toxin and immunity cassettes. Functional analyses indicated that VgrG, a specialized antibacterial effector, contains a C-terminal catalytically active glucosaminidase domain that is used to degrade prey peptidoglycan. Moreover, we confirmed that a bicistronic unit at the end of the T6SS1 cluster encodes a novel antibacterial T6SS effector and immunity pair. Together, these results demonstrate that Pab T6SS1 is an antibacterial system delivering a lysozyme-like effector to eliminate competitors, and indicate that this bacterium contains additional novel T6SS effectors.

中文翻译：

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Pantoea agglomerans pv 中的抗菌 T6SS。betae 提供一种类似溶菌酶的效应物来对抗竞争对手

VI 型分泌系统 (T6SS) 由许多革兰氏阴性细菌部署，以将毒性效应物传递到邻近细胞中。Pantoea agglomerans pv的基因组。betae ( Pab ) 植物病原细菌包含一个基因簇 (T6SS1)，预计会编码完整的 T6SS。使用分泌和竞争分析，我们发现Pab中的 T6SS1是一种功能性抗菌系统，可使这种病原体在与自然环境中发现的植物相关细菌的竞争中胜出。T6SS1 基因簇的计算分析表明，抗菌效应蛋白和免疫蛋白编码在三个基因组岛内，这些岛还包含孤儿免疫基因阵列或毒素和免疫盒。功能分析表明，VgrG 是一种专门的抗菌效应器，包含一个 C 端催化活性氨基葡萄糖苷酶结构域，用于降解猎物肽聚糖。此外，我们确认 T6SS1 簇末端的双顺反子单元编码一种新型抗菌 T6SS 效应子和免疫对。总之，这些结果表明PabT6SS1 是一种抗菌系统，可提供类似溶菌酶的效应物以消除竞争者，并表明该细菌含有额外的新型 T6SS 效应物。