Yu Shan, Wei Qing, Zhao Tianhu, Guo Yuan, Ma Luyan Z
State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China University of the Chinese Academy of Sciences, Beijing, China.
State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
Appl Environ Microbiol. 2016 Oct 14;82(21):6403-6413. doi: 10.1128/AEM.01307-16. Print 2016 Nov 1.
Exopolysaccharide Psl is a critical biofilm matrix component in Pseudomonas aeruginosa, which forms a fiber-like matrix to enmesh bacterial communities. Iron is important for P. aeruginosa biofilm development, yet it is not clearly understood how iron contributes to biofilm development. Here, we showed that iron promoted biofilm formation via elevating Psl production in P. aeruginosa The high level of iron stimulated the synthesis of Psl by reducing rhamnolipid biosynthesis and inhibiting the expression of AmrZ, a repressor of psl genes. Iron-stimulated Psl biosynthesis and biofilm formation held true in mucoid P. aeruginosa strains. Subsequent experiments indicated that iron bound with Psl in vitro and in biofilms, which suggested that Psl fibers functioned as an iron storage channel in P. aeruginosa biofilms. Moreover, among three matrix exopolysaccharides of P. aeruginosa, Psl is the only exopolysaccharide that can bind with both ferrous and ferric ion, yet with higher affinity for ferrous iron. Our data suggest a survival strategy of P. aeruginosa that uses exopolysaccharide to sequester and store iron to stimulate Psl-dependent biofilm formation.
Pseudomonas aeruginosa is an environmental microorganism which is also an opportunistic pathogen that can cause severe infections in immunocompromised individuals. It is the predominant airway pathogen causing morbidity and mortality in individuals affected by the genetic disease cystic fibrosis (CF). Increased airway iron and biofilm formation have been proposed to be the potential factors involved in the persistence of P. aeruginosa in CF patients. Here, we showed that a high level of iron enhanced the production of the key biofilm matrix exopolysaccharide Psl to stimulate Psl-dependent biofilm formation. Our results not only make the link between biofilm formation and iron concentration in CF, but also could guide the administration or use of iron chelators to interfere with biofilm formation in P. aeruginosa in CF patients. Furthermore, our data also imply a survival strategy of P. aeruginosa under high-iron environmental conditions.
胞外多糖Psl是铜绿假单胞菌中一种关键的生物膜基质成分，它形成一种纤维状基质来包裹细菌群落。铁对铜绿假单胞菌生物膜的形成很重要，但铁如何促进生物膜形成尚不清楚。在此，我们表明铁通过提高铜绿假单胞菌中Psl的产生来促进生物膜形成。高水平的铁通过减少鼠李糖脂生物合成并抑制psl基因的阻遏物AmrZ的表达来刺激Psl的合成。铁刺激的Psl生物合成和生物膜形成在黏液型铜绿假单胞菌菌株中也成立。随后的实验表明铁在体外和生物膜中与Psl结合，这表明Psl纤维在铜绿假单胞菌生物膜中起到铁储存通道的作用。此外，在铜绿假单胞菌的三种基质胞外多糖中，Psl是唯一能与亚铁离子和铁离子都结合的胞外多糖，但对亚铁离子的亲和力更高。我们的数据表明铜绿假单胞菌利用胞外多糖螯合和储存铁以刺激依赖Psl的生物膜形成的一种生存策略。
铜绿假单胞菌是一种环境微生物，也是一种机会致病菌，可在免疫功能低下的个体中引起严重感染。它是导致遗传性疾病囊性纤维化（CF）患者发病和死亡的主要气道病原体。气道中铁含量增加和生物膜形成被认为是铜绿假单胞菌在CF患者中持续存在的潜在因素。在此，我们表明高水平的铁增强了关键生物膜基质胞外多糖Psl的产生，以刺激依赖Psl的生物膜形成。我们的结果不仅建立了CF中生物膜形成与铁浓度之间的联系，还可以指导铁螯合剂的给药或使用，以干扰CF患者中铜绿假单胞菌的生物膜形成。此外，我们的数据还暗示了铜绿假单胞菌在高铁环境条件下的一种生存策略。
