Abstract：
Type VI secretion system (T6SS) is a potent weapon employed by various Pseudomonas species to compete with neighboring microorganisms for limited nutrients and ecological niches. However, the involvement of T6SS effectors in interbacterial competition within the phytopathogen Pseudomonas syringae remains unknown. In this study, we examined two T6SS clusters in a wild-type P. syringae MB03 and verified the involvement of one cluster, namely, T6SS-1, in interbacterial competition. Additionally, our results showed that two T6SS DNase effectors, specifically Tde1 and Tde4, effectively outcompeted antagonistic bacteria, with Tde4 playing a prominent role. Furthermore, we found several cognate immunity proteins, including Tde1ia, Tde1ib, and Tde4i, which are located in the downstream loci of their corresponding effector protein genes and worked synergistically to protect MB03 cells from self-intoxication. Moreover, expression of either Tde1 or C-terminus of Tde4 in Escherichia coli cells induced DNA degradation and changes in cell morphology. Thus, our results provide new insights into the role of the T6SS effectors of P. syringae in the interbacterial competition in the natural environment.
OBJECTIVE: The phytopathogen Pseudomonas syringae employs an active type VI secretion system (T6SS) to outcompete other microorganisms in the natural environment, particularly during the epiphytic growth in the phyllosphere. By examining two T6SS clusters in P. syringae MB03, T6SS-1 is found to be effective in killing Escherichia coli cells. We highlight the excellent antibacterial effect of two T6SS DNase effectors, namely, Tde1 and Tde4. Both of them function as nuclease effectors, leading to DNA degradation and cell filamentation in prey cells, ultimately resulting in cell death. Our findings deepen our understanding of the T6SS effector repertoires used in P. syringae and will facilitate the development of effective antibacterial strategies.
OBJECTIVE: The phytopathogen Pseudomonas syringae employs an active type VI secretion system (T6SS) to outcompete other microorganisms in the natural environment, particularly during the epiphytic growth in the phyllosphere. By examining two T6SS clusters in P. syringae MB03, T6SS-1 is found to be effective in killing Escherichia coli cells. We highlight the excellent antibacterial effect of two T6SS DNase effectors, namely, Tde1 and Tde4. Both of them function as nuclease effectors, leading to DNA degradation and cell filamentation in prey cells, ultimately resulting in cell death. Our findings deepen our understanding of the T6SS effector repertoires used in P. syringae and will facilitate the development of effective antibacterial strategies.
摘要：
VI型分泌系统（T6SS）是各种假单胞菌物种与邻近微生物竞争有限的营养和生态位的有效武器。然而,目前尚不清楚T6SS效应子是否参与了丁香假单胞菌体内的细菌间竞争.在这项研究中,我们检查了野生型丁香假单胞菌MB03中的两个T6SS簇，并验证了一个簇的参与，即,T6SS-1，在细菌间竞争中。此外,我们的结果表明，两个T6SSDNA酶效应子，特别是Tde1和Tde4，有效地胜过拮抗细菌，Tde4发挥了重要作用。此外，我们发现了几种同源免疫蛋白，包括Tde1ia,Tde1ib,还有Tde4i,它们位于其相应的效应蛋白基因的下游基因座，并协同作用以保护MB03细胞免受自我中毒。此外，在大肠杆菌细胞中Tde1或Tde4的C末端的表达诱导DNA降解和细胞形态的变化。因此，我们的研究结果为丁香假单胞菌T6SS效应子在自然环境中细菌间竞争中的作用提供了新的见解。
目的：植物病原体丁香假单胞菌利用活跃的VI型分泌系统（T6SS）在自然环境中胜过其他微生物，特别是在叶球的附生生长过程中。通过检查丁香假单胞菌MB03中的两个T6SS簇，发现T6SS-1可有效杀死大肠杆菌细胞。我们强调了两种T6SSDNA酶效应物的优异抗菌作用，即,Tde1和Tde4。它们都是核酸酶效应物,导致猎物细胞中的DNA降解和细胞丝状化，最终导致细胞死亡。我们的发现加深了我们对丁香假单胞菌中使用的T6SS效应库的理解，并将促进有效抗菌策略的开发。
目的：植物病原体丁香假单胞菌利用活跃的VI型分泌系统（T6SS）在自然环境中胜过其他微生物，特别是在叶球的附生生长过程中。通过检查丁香假单胞菌MB03中的两个T6SS簇，发现T6SS-1可有效杀死大肠杆菌细胞。我们强调了两种T6SSDNA酶效应物的优异抗菌作用，即,Tde1和Tde4。它们都是核酸酶效应物,导致猎物细胞中的DNA降解和细胞丝状化，最终导致细胞死亡。我们的发现加深了我们对丁香假单胞菌中使用的T6SS效应库的理解，并将促进有效抗菌策略的开发。
