期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：36
页码：11353-11358
DOI：10.1073/pnas.1503058112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceExopolysaccharides and extracellular DNA are important structural components that contribute to the self-assembly of large aggregates or microcolonies that are characteristic of biofilms. Pseudomonas aeruginosa is capable of producing multiple exopolysaccharides, including alginate, Psl, and Pel. At present, little is known about Pel's chemical structure and its role in microcolony formation. Our results demonstrate that Pel is composed of cationic amino sugars. Using this knowledge, we have developed a Pel-specific lectin stain to directly visualize Pel in biofilms. We show that the positive charge on Pel facilitates its binding to extracellular DNA in the biofilm stalk, and that Pel can compensate for lack of Psl in the biofilm periphery. Biofilm formation is a complex, ordered process. In the opportunistic pathogen Pseudomonas aeruginosa, Psl and Pel exopolysaccharides and extracellular DNA (eDNA) serve as structural components of the biofilm matrix. Despite intensive study, Pel's chemical structure and spatial localization within mature biofilms remain unknown. Using specialized carbohydrate chemical analyses, we unexpectedly found that Pel is a positively charged exopolysaccharide composed of partially acetylated 1[->]4 glycosidic linkages of N-acetylgalactosamine and N-acetylglucosamine. Guided by the knowledge of Pel's sugar composition, we developed a tool for the direct visualization of Pel in biofilms by combining Pel-specific Wisteria floribunda lectin staining with confocal microscopy. The results indicate that Pel cross-links eDNA in the biofilm stalk via ionic interactions. Our data demonstrate that the cationic charge of Pel is distinct from that of other known P. aeruginosa exopolysaccharides and is instrumental in its ability to interact with other key biofilm matrix components.
关键词：biofilms ; exopolysaccharide ; extracellular DNA ; Pel ; Psl
