Type VI secretion system of Pseudomonas aeruginosa is associated with biofilm formation but not environmental adaptation
Type VI secretion system of Pseudomonas aeruginosa is associated with biofilm formation but not environmental adaptation
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DOI：
10.1002/mbo3.991
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发表时间：
2020-01-21
期刊：
影响因子：
3.4
通讯作者：
Wu, Yong
中科院分区：
文献类型：
--
作者：
Chen, Lihua;Zou, Yaru;Wu, Yong
铜绿假单胞菌编码三种VI型分泌系统(T6SS)，即H1-、H2-和H3-T6SS。铜绿假单胞菌溶血素共调节蛋白(Hcp)是T6SS的效应蛋白和标志。虽然T6SS普遍存在并影响生态和人类健康，但其一般机制和生理作用仍不完全清楚。因此，在本研究中，我们研究了铜绿假单胞菌T6SS对生物膜形成和环境适应的影响。为此，我们收集了铜绿假单胞菌临床分离株，根据它们的生物被膜形成能力将其分为强生物被膜形成组(SBF)和非生物被膜形成组(NBF)，并比较了它们的相关临床特征。SBF感染患者的住院时间明显长于NBF感染患者。SBF组T6SS相关基因(hcp1、hcp3)和群体感应基因(LasR)的表达水平高于NBF组。此外，LasR与hcp1的表达水平呈负相关，与hcp2、hcp3的表达水平呈正相关。此外，我们还检测了T6SS相关基因和生物膜相关基因在铜绿假单胞菌PAO1浮游细胞和生物膜细胞中的表达，并构建了PAO1oclpV1菌株来研究H1-T6SS的适应特性。与浮游细胞相比，PAO1生物膜细胞中hcp1、hcp2、hcp3、lasR等生物膜相关基因的表达水平显著升高。但PAO1oclpV1和PAO1野生型菌株在生物膜形成能力、生物膜相关基因表达、附着能力、生长特性、耐酸、耐渗透压、表面结构和形态等方面均无显著差异。综上所述，我们的结果表明T6SS可能在铜绿假单胞菌生物膜的形成中起作用，而H1-T6SS对环境适应没有贡献。
Pseudomonas aeruginosa encodes three type VI secretion systems (T6SSs), namely H1-, H2-, and H3-T6SS. P. aeruginosa hemolysin-coregulated protein (Hcp) is the effector protein and the hallmark of T6SS. Although T6SS is ubiquitous and affects ecology and human health, its general mechanism and physiological role are still not fully understood. Therefore, in this study, we investigated the impact of the P. aeruginosa T6SS on biofilm formation and environmental adaptation. To this end, we collected P. aeruginosa clinical isolates, divided them into strong biofilm formation (SBF) and nonbiofilm formation (NBF) groups based on their biofilm-forming ability, and compared their associated clinical characteristics. The duration of hospitalization was longer in patients infected with SBF than those infected with NBF strains. The expression levels of T6SS-related genes (hcp1 and hcp3) and a quorum-sensing gene (lasR) were higher in the SBF group as compared to those in the NBF group. In addition, the expression level of lasR was negatively associated with that of hcp1, but was positively associated with those of hcp2 and hcp3. Moreover, we evaluated the expression of T6SS- and biofilm-associated genes in planktonic and biofilm cells of the P. aeruginosa strain PAO1, and constructed strain PAO1oclpV1 to study the adaptation characteristics of H1-T6SS. The expression levels of hcp1, hcp2, hcp3, lasR, and other biofilm-associated genes were significantly higher in PAO1 biofilm cells as compared to those of planktonic cells. However, except for swarming ability as a vital feature for biofilm formation, there were no significant differences in the biofilm-forming ability and expression of biofilm-associated genes, adherence ability, growth characteristics, resistance to acid and osmotic pressure, surface structure, and morphology between the PAO1oclpV1 and PAO1 wild-type strains. Collectively, our results suggest that T6SS might play a role in biofilm formation and that H1-T6SS does not contribute to environmental adaptation in P. aeruginosa.