Many bacterial cell surface glycans, such as the O antigen component of lipopolysaccharide (LPS), are produced via the so-called Wzx/Wzy- or ABC transporter-dependent pathways. O antigens are highly diverse polysaccharides that protect bacteria from their environment and engage in important host-pathogen interactions. The specific structure and composition of O antigens are the basis of classifying bacteria into O serotypes. In the opportunistic pathogen Pseudomonas aeruginosa, there are currently 20 known O-specific antigen (OSA) structures. The clusters of genes responsible for 18 of these O antigens have been identified, all of which follow the Wzx/Wzy-dependent pathway and are located at a common locus. In this study, we located the two unidentified O antigen biosynthesis clusters responsible for the synthesis of the O15 and the O17 OSA structures by analyzing published whole-genome sequence data. Intriguingly, these clusters were found outside the conserved OSA biosynthesis locus and were likely acquired through multiple horizontal gene transfer events. Based on data from knockout and overexpression studies, we determined that the synthesis of these O antigens follows an ABC transporter-dependent rather than a Wzx/Wzy-dependent pathway. In addition, we collected evidence to show that the O15 and O17 polysaccharide chain lengths are regulated by molecular rulers with distinct and variable domain architectures. The findings in this report are critical for a comprehensive understanding of O antigen biosynthesis in P. aeruginosa and provide a framework for future studies.

中文翻译：

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铜绿假单胞菌O17和O15 O特异抗原生物合成基因座的鉴定揭示了依赖ABC转运蛋白的合成途径和遗传多样性的机制。

许多细菌细胞表面聚糖，例如脂多糖（LPS）的O抗原成分，都是通过所谓的Wzx / Wzy或ABC转运蛋白依赖性途径产生的。O抗原是高度多样化的多糖，可保护细菌免受环境污染并参与重要的宿主-病原体相互作用。O抗原的特定结构和组成是将细菌分类为O血清型的基础。在机会病原体中，铜绿假单胞菌，目前有20种已知的O特异性抗原（OSA）结构。已经鉴定出负责这些O抗原中的18种的基因簇，所有这些簇都遵循Wzx / Wzy依赖性途径，并且位于一个共同的基因座。在这项研究中，我们通过分析已发布的全基因组序列数据，找到了负责O15和O17 OSA结构合成的两个未确定的O抗原生物合成簇。有趣的是，这些簇是在保守的OSA生物合成位点之外发现的，很可能是通过多个水平基因转移事件获得的。基于来自基因敲除和过表达研究的数据，我们确定这些O抗原的合成遵循ABC转运蛋白依赖性而不是Wzx / Wzy依赖性途径。此外，我们收集的证据表明，O15和O17多糖链的长度受具有独特和可变域结构的分子标尺调控。本报告中的发现对于全面了解O抗原的生物合成至关重要。铜绿假单胞菌并为将来的研究提供了框架。