Some Salmonella isolates produce an enigmatic, transient antigen known as T1. Here, Kelly et al. show that T1 is a complex linear glycan linked to lipid A–core, like a typical O antigen, and is expressed in a phase-variable manner regulated by recombinational inversion of a promoter upstream of the T1 genetic locus.
- Steven D. Kelly
- Mikel Jason Allas
- Chris Whitfield
