Yang Yantao, Pan Damin, Tang Yanan, Li Jiali, Zhu Kaixiang, Yu Zonglan, Zhu Lingfang, Wang Yao, Chen Peng, Li Changfu
State Key Laboratory of Crop Stress Biology for Arid Areas, Shaanxi Key Laboratory of Agricultural and Environmental Microbiology, College of Life Sciences, Northwest A&F University, Yangling, 712100, Shaanxi, China.
Stress Biol. 2022 Dec 28;2(1):55. doi: 10.1007/s44154-022-00078-7.
Microbial species often occur in complex communities and exhibit intricate synergistic and antagonistic interactions. To avoid predation and compete for favorable niches, bacteria have evolved specialized protein secretion systems. The type VI secretion system (T6SS) is a versatile secretion system widely distributed among Gram-negative bacteria that translocates effectors into target cells or the extracellular milieu via various physiological processes. Pseudomonas aeruginosa is an opportunistic pathogen responsible for many diseases, and it has three independent T6SSs (H1-, H2-, and H3-T6SS). In this study, we found that the H3-T6SS of highly virulent P. aeruginosa PA14 is negatively regulated by OxyR and OmpR, which are global regulatory proteins of bacterial oxidative and acid stress. In addition, we identified a H3-T6SS effector PA14_33970, which is located upstream of VgrG3. PA14_33970 interacted directly with VgrG3 and translocated into host cells. Moreover, we found that H3-T6SS and PA14_33970 play crucial roles in oxidative, acid, and osmotic stress resistance, as well as in motility and biofilm formation. PA14_33970 was identified as a new T6SS effector promoting biofilm formation and thus named TepB. Furthermore, we found that TepB contributes to the virulence of P. aeruginosa PA14 toward Caenorhabditis elegans. Overall, our study indicates that H3-T6SS and its biofilm-promoting effector TepB are regulated by OxyR and OmpR, both of which are important for adaptation of P. aeruginosa PA14 to multiple stressors, providing insights into the regulatory mechanisms and roles of T6SSs in P. aeruginosa.
微生物物种通常以复杂群落的形式出现，并表现出复杂的协同和拮抗相互作用。为了避免被捕食并竞争有利的生态位，细菌进化出了专门的蛋白质分泌系统。VI型分泌系统（T6SS）是一种广泛存在于革兰氏阴性菌中的多功能分泌系统，它通过各种生理过程将效应蛋白转运到靶细胞或细胞外环境中。铜绿假单胞菌是一种引起多种疾病的机会致病菌，它有三个独立的T6SS（H1-T6SS、H2-T6SS和H3-T6SS）。在本研究中，我们发现高毒力铜绿假单胞菌PA14的H3-T6SS受到OxyR和OmpR的负调控，这两种蛋白是细菌氧化应激和酸应激的全局调控蛋白。此外，我们鉴定出一种H3-T6SS效应蛋白PA14_33970，它位于VgrG3的上游。PA14_33970直接与VgrG3相互作用并转运到宿主细胞中。此外，我们发现H3-T6SS和PA14_33970在氧化应激、酸应激和渗透压应激抗性以及运动性和生物膜形成中起关键作用。PA14_33970被鉴定为一种促进生物膜形成的新型T6SS效应蛋白，因此命名为TepB。此外，我们发现TepB有助于铜绿假单胞菌PA14对秀丽隐杆线虫的毒力。总体而言，我们的研究表明H3-T6SS及其促进生物膜形成的效应蛋白TepB受OxyR和OmpR调控，这两者对于铜绿假单胞菌PA14适应多种应激源都很重要，为T6SS在铜绿假单胞菌中的调控机制和作用提供了见解。
