Since phages present a major challenge to survival in most environments, bacteria express a battery of anti-phage defences including CRISPR-Cas, restriction-modification and abortive infection systems ^1-4 . Such strategies are effective, but the phage genome-which encodes potentially inhibitory gene products-is still allowed to enter the cell. The safest way to preclude phage infection is to block initial phage adsorption to the cell. Here, we describe a cell-surface modification that blocks infection by certain phages. Strains of the opportunistic pathogen Pseudomonas aeruginosa express one of five different type IV pilins (T4P) ⁵ , two of which are glycosylated with O-antigen units ⁶ or polymers of D-arabinofuranose ^7-9 . We propose that predation by bacteriophages that use T4P as receptors selects for strains that mask potential phage binding sites using glycosylation. Here, we show that both modifications protect P. aeruginosa from certain pilus-specific phages. Alterations to pilin sequence can also block phage infection, but glycosylation is considered less likely to create disadvantageous phenotypes. Through construction of chimeric phages, we show that specific phage tail proteins allow for infection of strains with glycosylated pili. These studies provide insight into first-line bacterial defences against predation and ways in which phages circumvent them, and provide a rationale for the prevalence of pilus glycosylation in nature.

中文翻译：

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铜绿假单胞菌通过IV型菌毛糖基化防御噬菌体。

由于噬菌体在大多数环境中对生存提出了重大挑战，细菌表达了一系列抗噬菌体防御功能，包括CRISPR-Cas，限制性修饰和流产感染系统^1-4。这种策略是有效的，但是仍然允许编码潜在抑制性基因产物的噬菌体基因组进入细胞。防止噬菌体感染的最安全方法是阻止最初的噬菌体吸附到细胞上。在这里，我们描述了阻止某些噬菌体感染的细胞表面修饰。机会病原性铜绿假单胞菌菌株表达五种不同的IV型菌毛素（T4P）^{5中的一种}，其中两种被O-抗原单元⁶糖基化或D-阿拉伯呋喃糖^7-9的聚合物。我们建议使用T4P作为受体的噬菌体进行捕食，选择使用糖基化掩盖潜在噬菌体结合位点的菌株。在这里，我们表明这两种修饰都可以保护铜绿假单胞菌免受某些菌毛特异性噬菌体的侵害。菌毛蛋白序列的改变也可以阻断噬菌体感染，但是糖基化被认为不太可能产生不利的表型。通过嵌合噬菌体的构建，我们表明特定的噬菌体尾部蛋白允许用糖基化菌毛感染菌株。这些研究提供了对捕食的一线细菌防御以及噬菌体规避它们的方式的见识，并为菌毛糖基化在自然界中的流行提供了理论依据。