The Bacteroidetes phylum is renowned for its ability to degrade a wide range of complex carbohydrates, a trait that has enabled its dominance in many diverse environments. The best studied species inhabit the human gut microbiome and use polysaccharide utilization loci (PULs), discrete genetic structures that encode proteins involved in the sensing, binding, deconstruction, and import of target glycans. In many environmental species, polysaccharide degradation is tightly coupled to the phylum-exclusive type IX secretion system (T9SS), which is used for the secretion of certain enzymes and is linked to gliding motility. In addition, within specific species these two adaptive systems (PULs and T9SS) are intertwined, with PUL-encoded enzymes being secreted by the T9SS. Here, we discuss the most noteworthy PUL and non-PUL mechanisms that confer specific and rapid polysaccharide degradation capabilities to the Bacteroidetes in a range of environments. We also acknowledge that the literature showcasing examples of PULs is rapidly expanding and developing a set of assumptions that can be hard to track back to original findings. Therefore, we present a simple universal description of conserved PUL functions and how they are determined, while proposing a common nomenclature describing PULs and their components, to simplify discussion and understanding of PUL systems.

中文翻译：

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拟杆菌对多糖的降解：机制和命名

拟杆菌门以其降解多种复杂碳水化合物的能力而闻名，这一特性使其在许多不同的环境中占据主导地位。研究得最好的物种栖息在人类肠道微生物组中，并使用多糖利用基因座 (PUL)，这是一种离散的遗传结构，编码参与目标聚糖的传感、结合、解构和输入的蛋白质。在许多环境物种中，多糖降解与门独有的 IX 型分泌系统 (T9SS) 紧密耦合，该系统用于分泌某些酶并与滑翔运动有关。此外，在特定物种中这两个自适应系统（PUL 和 T9SS）相互交织，PUL 编码的酶由 T9SS 分泌。在这里，我们讨论了最值得注意的 PUL 和非 PUL 机制，它们在一系列环境中赋予拟杆菌特定和快速的多糖降解能力。我们还承认，展示 PUL 示例的文献正在迅速扩展并发展出一组难以追溯到原始发现的假设。因此，我们提出了保守 PUL 函数及其确定方式的简单通用描述，同时提出了描述 PUL 及其组件的通用命名法，以简化对 PUL 系统的讨论和理解。