N-Acetylneuraminic acid is the most abundant sialic acid (SA) in humans and is expressed as the terminal sugar on intestinal mucus glycans. Several pathogenic bacteria harvest and display host SA on their own surfaces to evade Siglec-mediated host immunity. While previous studies have identified bacterial enzymes associated with SA catabolism, no reported methods permit the selective labeling, tracking, and quantitation of SA-presenting microbes within complex multi-microbial systems. We combined metabolic labeling, click chemistry, 16S rRNA gene, and whole-genome sequencing to track and identify SA-presenting microbes from a cultured human fecal microbiome. We isolated a new strain of Escherichia coli that incorporates SA onto its own surface and encodes for the nanT, neuA, and neuS genes necessary for harvesting and presenting SA. Our method is applicable to the identification of SA-presenting bacteria from human, animal, and environmental microbiomes, as well as providing an entry point for the investigation of surface-expressed SA-associated structures.

N-乙酰神经氨酸是人体中含量最丰富的唾液酸 (SA)，表现为肠粘液聚糖上的末端糖。几种致病菌在其自身表面收获和展示宿主 SA，以逃避 Siglec 介导的宿主免疫。虽然以前的研究已经确定了与 SA 分解代谢相关的细菌酶，但没有报道的方法允许在复杂的多微生物系统中选择性标记、跟踪和定量 SA 呈递微生物。我们结合代谢标记、点击化学、16S rRNA 基因和全基因组测序来跟踪和鉴定来自培养的人类粪便微生物组的 SA 呈递微生物。我们分离出一种新的大肠杆菌菌株，该菌株将 SA 结合到其自身表面并编码nanT，neuA和neuS基因是获取和呈递 SA 所必需的。我们的方法适用于从人类、动物和环境微生物组中鉴定呈递 SA 的细菌，并为研究表面表达的 SA 相关结构提供一个切入点。