Kelly Steven D, Allas Mikel Jason, Goodridge Lawrence D, Lowary Todd L, Whitfield Chris
Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada.
Department of Chemistry, University of Alberta, Edmonton, AB, Canada.
Nat Commun. 2024 Aug 2;15(1):6504. doi: 10.1038/s41467-024-50957-y.
The bacterial genus Salmonella includes diverse isolates with multiple variations in the structure of the main polysaccharide component (O antigen) of membrane lipopolysaccharides. In addition, some isolates produce a transient (T) antigen, such as the T1 polysaccharide identified in the 1960s in an isolate of Salmonella enterica Paratyphi B. The structure and biosynthesis of the T1 antigen have remained enigmatic. Here, we use biophysical, biochemical and genetic methods to show that the T1 antigen is a complex linear glycan containing tandem homopolymeric domains of galactofuranose and ribofuranose, linked to lipid A-core, like a typical O antigen. T1 is a phase-variable antigen, regulated by recombinational inversion of the promoter upstream of the T1 genetic locus through a mechanism not observed for other bacterial O antigens. The T1 locus is conserved across many Salmonella isolates, but is mutated or absent in most typhoidal serovars and in serovar Enteritidis.
沙门氏菌属包含多种分离株，其膜脂多糖的主要多糖成分（O抗原）结构存在多种变异。此外，一些分离株会产生一种瞬时（T）抗原，比如20世纪60年代在甲型副伤寒沙门氏菌的一个分离株中鉴定出的T1多糖。T1抗原的结构和生物合成一直是个谜。在此，我们运用生物物理、生化和遗传学方法表明，T1抗原是一种复杂的线性聚糖，含有半乳呋喃糖和核糖呋喃糖的串联同聚结构域，与脂多糖核心相连，如同典型的O抗原。T1是一种相变抗原，通过T1基因座上游启动子的重组倒位进行调控，这一机制在其他细菌O抗原中未被观察到。T1基因座在许多沙门氏菌分离株中是保守的，但在大多数伤寒血清型和肠炎血清型中发生了突变或缺失。
