The swimming device of archaea—the archaellum—presents asparagine (N)-linked glycans. While N-glycosylation serves numerous roles in archaea, including enabling their survival in extreme environments, how this post-translational modification contributes to cell motility remains under-explored. Here, we report the cryo-EM structure of archaellum filaments from the haloarchaeon Halobacterium salinarum, where archaellins, the building blocks of the archaellum, are N-glycosylated, and the N-glycosylation pathway is well-resolved. We further determined structures of archaellum filaments from two N-glycosylation mutant strains that generate truncated glycans and analyzed their motility. While cells from the parent strain exhibited unidirectional motility, the N-glycosylation mutant strain cells swam in ever-changing directions within a limited area. Although these mutant strain cells presented archaellum filaments that were highly similar in architecture to those of the parent strain, N-linked glycan truncation greatly affected interactions between archaellum filaments, leading to dramatic clustering of both isolated and cell-attached filaments. We propose that the N-linked tetrasaccharides decorating archaellins act as physical spacers that minimize the archaellum filament aggregation that limits cell motility.

古细菌的游泳装置——古细菌——呈现出天冬酰胺 (N) 连接的聚糖。虽然 N-糖基化在古细菌中发挥着多种作用，包括使其能够在极端环境中生存，但这种翻译后修饰如何促进细胞运动仍有待探索。在这里，我们报告了来自盐古细菌盐杆菌的古菌丝的冷冻电镜结构，其中古菌素（古菌的组成部分）被N-糖基化，并且N-糖基化途径得到了很好的解析。我们进一步确定了两种产生截短聚糖的 N-糖基化突变菌株的古细菌丝的结构，并分析了它们的运动性。亲本菌株的细胞表现出单向运动，而 N-糖基化突变菌株的细胞在有限的区域内以不断变化的方向游动。尽管这些突变菌株细胞呈现出在结构上与亲本菌株高度相似的古菌丝，但 N 连接聚糖截短极大地影响了古菌丝之间的相互作用，导致分离的丝和细胞附着的丝显着聚集。我们提出装饰古菌素的 N-连接四糖充当物理间隔物，最大限度地减少限制细胞运动的古菌丝聚集。