Pleiotropic effect of Francisella ABC transporter gene inactivation on production of glycoconjugates

The present study deals with the cross-talk of polysaccharide biosynthesis pathways of a highly infectious intracellular pathogen Francisella tularensis, the causative agent of tularemia. We have studied the consequences of disrupting the FTS_1402 gene that lies within the putative polysaccharide locus FTT0789-FTT0800 on production of glycoconjugates and host-pathogen associated properties. Based on the homology to campylobacterial PglK flippase, FTS_1402 was predicted to play a role in glycosylation as a transporter of the nascent glycan across the inner membrane before its addition to target protein. Surprisingly, an inactivation of FTS_1402 gene had a pleiotropic effect upon production of multiple surface glycoconjugates. We show that FTS_1402 encoded protein is required for complete glycosylation but also for biogenesis of other surface exopolysaccharides such as lipopolysaccharide, capsule and/or capsule-like complex. All monitored glycoconjugates had preserved structures but were synthesized in lower amounts when compared to the highly virulent parental strain. Inactivation of FTS_1402 had an unexpectedly marked impact on virulence of the mutant, which however, provided protection against subsequent systemic challenge. With particular respect to protein glycosylation in the mutant and a wild type FSC200 strain, we here provide relevant MS data.