Pseudomonas syringae is a phytopathogenic model bacterium that is used worldwide to study plant–bacteria interactions and biofilm formation in association with a plant host. Within this species, the syringae pathovar is the most studied due to its wide host range, affecting both, woody and herbaceous plants. In particular, Pseudomonas syringae pv. syringae (Pss) has been previously described as the causal agent of bacterial apical necrosis on mango trees. Pss exhibits major epiphytic traits and virulence factors that improve its epiphytic survival and pathogenicity in mango trees. The cellulose exopolysaccharide has been described as a key component in the development of the biofilm lifestyle of the P. syringae pv. syringae UMAF0158 strain (PssUMAF0158). PssUMAF0158 contains two additional genomic regions that putatively encode for exopolysaccharides such as alginate and a Psl-like polysaccharide. To date, the Psl polysaccharide has only been studied in Pseudomonas aeruginosa, in which it plays an important role during biofilm development. However, its function in plant-associated bacteria is still unknown. To understand how these exopolysaccharides contribute to the biofilm matrix of PssUMAF0158, knockout mutants of genes encoding these putative exopolysaccharides were constructed. Flow-cell chamber experiments revealed that cellulose and the Psl-like polysaccharide constitute a basic scaffold for biofilm architecture in this bacterium. Curiously, the Psl-like polysaccharide of PssUMAF0158 plays a role in virulence similar to what has been described for cellulose. Finally, the impaired swarming motility of the Psl-like exopolysaccharide mutant suggests that this exopolysaccharide may play a role in the motility of PssUMAF0158 over the mango plant surface.

丁香假单胞菌是一种植物致病模型细菌，在全世界范围内用于研究植物与细菌的相互作用以及与植物宿主相关的生物膜形成。在该物种中，丁香致病菌因其寄主范围广泛而受到最多的研究，同时影响木本和草本植物。特别是丁香假单胞菌pv。丁香菌（Pss）先前被描述为芒果树细菌性顶端坏死的致病因子。Pss 表现出主要的附生性状和毒力因子，可提高其在芒果树中的附生存活率和致病性。纤维素胞外多糖已被描述为丁香假单胞菌生物膜生活方式发展的关键成分。丁香菌 UMAF0158 菌株（PssUMAF0158）。PssUMAF0158 包含两个额外的基因组区域，推测编码胞外多糖，例如藻酸盐和 Psl 样多糖。迄今为止，Psl多糖仅在铜绿假单胞菌中进行了研究，它在生物膜形成过程中发挥着重要作用。然而，它在植物相关细菌中的功能仍然未知。为了了解这些胞外多糖如何对 PssUMAF0158 的生物膜基质做出贡献，构建了编码这些假定的胞外多糖的基因的敲除突变体。流动池实验表明，纤维素和 Psl 样多糖构成了该细菌生物膜结构的基本支架。奇怪的是，PssUMAF0158 的 Psl 样多糖在毒力方面所起的作用与所描述的纤维素类似。最后，Psl 样胞外多糖突变体的集群运动受损表明，这种胞外多糖可能在 PssUMAF0158 在芒果植株表面的运动中发挥作用。