Li Yanqi, Chen Lin, Zhang Pansong, Bhagirath Anjali Y, Duan Kangmin
Department of Oral Biology, Rady Faculty of Health Sciences, University of Manitoba, Winnipeg, MB, Canada.
College of Life Sciences, Northwest University, Xi'an, China.
Front Microbiol. 2020 May 29;11:1096. doi: 10.3389/fmicb.2020.01096. eCollection 2020.
The type VI secretion system (T6SS) is a toxic effector delivery apparatus widely distributed in Gram-negative bacteria. The opportunistic pathogen encodes three T6SSs, namely H1-, H2-, and H3-T6SS. Each T6SS possesses its own effectors and their roles are not yet fully understood. Here, we report that an H3-T6SS deletion mutant PAO1(Δ) significantly affected the virulence-related phenotypes including pyocyanin production, biofilm formation, proteolytic activity, and motilities. Most interestingly, the expression of T3SS genes was markedly affected, indicating a link between H3-T6SS and T3SS. RNA-Sequencing was performed to globally identify the genes differentially expressed when H3-T6SS was inactivated and the results obtained correlated well with the observed phenotypes. Interestingly, the expressions of T2SS, T3SS, H2-T6SS, and H3-T6SS were all significantly decreased, while H1-T6SS was increased in the PAO1(Δ) strain. We also observed that the intracellular concentration of secondary messenger cAMP was reduced in PAO1(Δ), and the c-di-GMP level was also decreased as indicated by the decreased reporter activity. Finally, by using a infection model, we show that H3-T6SS plays a key role in the pathogenicity of . Overall, our study highlights the unique connection of H3-T6SS in with T3SS, pyocyanin production, biofilm formation and pathogenicity.
VI型分泌系统（T6SS）是一种广泛分布于革兰氏阴性菌中的毒性效应物递送装置。这种机会致病菌编码三种T6SS，即H1-T6SS、H2-T6SS和H3-T6SS。每个T6SS都有其自身的效应物，其作用尚未完全明确。在此，我们报告H3-T6SS缺失突变体PAO1（Δ）显著影响了与毒力相关的表型，包括绿脓菌素产生、生物膜形成、蛋白水解活性和运动性。最有趣的是，III型分泌系统（T3SS）基因的表达受到显著影响，表明H3-T6SS与T3SS之间存在联系。进行了RNA测序以全面鉴定H3-T6SS失活时差异表达的基因，所得结果与观察到的表型高度相关。有趣的是，在PAO1（Δ）菌株中，II型分泌系统（T2SS）、T3SS、H2-T6SS和H3-T6SS的表达均显著降低，而H1-T6SS的表达则增加。我们还观察到PAO1（Δ）中第二信使环磷酸腺苷（cAMP）的细胞内浓度降低，并且如报告基因活性降低所示，环二鸟苷酸（c-di-GMP）水平也降低。最后，通过使用感染模型，我们表明H3-T6SS在该菌的致病性中起关键作用。总体而言，我们的研究突出了该菌中H3-T6SS与T3SS、绿脓菌素产生、生物膜形成及该菌致病性之间的独特联系。
