Pseudomonas aeruginosa is an important pathogen that causes chronic infections that involve multicellular aggregates called biofilms. Within biofilms, bacteria are surrounded in a protective extracellular matrix of proteins, exopolysaccharides (EPS), and DNA. A key P. aeruginosa matrix protein is an extracellular adhesin called CdrA, which promotes aggregation by binding to the EPS Psl and via CdrA-CdrA interactions. We hypothesized that because of its ability to bind Psl, CdrA would be important only for strains that use Psl as the primary EPS (e.g., the laboratory strain PAO1). Thus, we predicted that cdrA might be dispensable for biofilm formation by strains that do not utilize Psl (e.g., the laboratory strain PA14). Instead, we observed that cdrA deletion strains exhibited biofilm defects, regardless of their EPS dependencies. We screened a panel of clinical and environmental P. aeruginosa isolates for the presence of the cdrA allele and production of CdrA protein. All isolates that we tested contained the cdrA allele, and these alleles had minimal sequence variation compared to the reference PAO1 cdrA gene. Additionally, all isolates except one produced detectable CdrA protein. We investigated the possible mechanisms of CdrA-promoted biofilm formation in these strains where Psl is not dominant, and we discovered that CdrA binds to Pel. Although Psl and Pel chemical structures are distinct, this appears to be a specific interaction, since previous work has shown that CdrA binds discriminately to other EPS. Our findings provide new understanding of biofilm formation across P. aeruginosa isolates and emphasize the versatility of CdrA.

中文翻译：

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多功能铜绿假单胞菌生物膜基质蛋白 CdrA 通过不同的细胞外胞外多糖相互作用促进聚集。

铜绿假单胞菌是一种重要的病原体，可引起涉及称为生物膜的多细胞聚集体的慢性感染。在生物膜内，细菌被蛋白质、胞外多糖 (EPS) 和 DNA 组成的保护性细胞外基质包围。一种关键的铜绿假单胞菌基质蛋白是一种称为 CdrA 的细胞外粘附素，它通过与 EPS Psl 结合并通过 CdrA-CdrA 相互作用促进聚集。我们假设由于其结合 Psl 的能力，CdrA 仅对使用 Psl 作为主要 EPS 的菌株（例如，实验室菌株 PAO1）很重要。因此，我们预测cdrA可能对于不利用 Psl 的菌株（例如，实验室菌株 PA14）的生物膜形成是可有可无的。相反，我们观察到cdrA缺失菌株表现出生物膜缺陷，无论它们的EPS依赖性如何。我们筛选了一组临床和环境铜绿假单胞菌分离株中是否存在cdrA等位基因和产生 CdrA 蛋白。我们测试的所有分离株都含有cdrA等位基因，与参考 PAO1 cdrA相比，这些等位基因的序列变异最小基因。此外，除一种分离株外，所有分离株均产生可检测的 CdrA 蛋白。我们研究了在这些 Psl 不占优势的菌株中 CdrA 促进生物膜形成的可能机制，我们发现 CdrA 与 Pel 结合。尽管 Psl 和 Pel 化学结构不同，但这似乎是一种特定的相互作用，因为以前的工作表明 CdrA 可区别地与其他 EPS 结合。我们的研究结果提供了对铜绿假单胞菌生物膜形成的新认识，并强调了 CdrA 的多功能性。