Department of Clinical Laboratory, The Third Xiangya Hospital, Central South University, Changsha, China.
Microbiologyopen. 2020 Mar;9(3):e991. doi: 10.1002/mbo3.991. Epub 2020 Jan 21.
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 PAO1△clpV1 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 PAO1△clpV1 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.
铜绿假单胞菌编码三种类型 VI 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）是效应蛋白，也是 T6SS 的标志。尽管 T6SS 普遍存在且影响生态和人类健康，但它的一般机制和生理作用仍未完全了解。因此，在这项研究中，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，根据其生物膜形成能力将其分为强生物膜形成（SBF）和非生物膜形成（NBF）组，并比较了它们相关的临床特征。与感染 NBF 株的患者相比，感染 SBF 株的患者住院时间更长。与 NBF 组相比，SBF 组的 T6SS 相关基因（hcp1 和 hcp3）和群体感应基因（lasR）的表达水平更高。此外，lasR 的表达水平与 hcp1 的表达水平呈负相关，但与 hcp2 和 hcp3 的表达水平呈正相关。此外，我们评估了铜绿假单胞菌 PAO1 株浮游细胞和生物膜细胞中 T6SS 和生物膜相关基因的表达情况，并构建了 PAO1△clpV1 菌株以研究 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 和其他生物膜相关基因的表达水平显著更高。然而，除了生物膜形成的重要特征——群集能力外，PAO1△clpV1 和 PAO1 野生型菌株之间的生物膜形成能力和生物膜相关基因的表达、粘附能力、生长特性、耐酸和耐渗透压能力、表面结构和形态没有显著差异。综上所述，我们的研究结果表明，T6SS 可能在生物膜形成中发挥作用，而 H1-T6SS 并不有助于铜绿假单胞菌的环境适应。
