The biosynthesis and role of phosphorylcholine in pathogenic and nonpathogenic bacteria

Phosphorylcholine (ChoP) is found in a variety of prokaryotic and eukaryotic organisms. It is now recognized as a critical modification of the surface structures of bacteria with roles in bacterial pathogenesis.In bacteria containing ChoP-modified glycoconjugates, the Lic-1 pathway mediates the transformation of environmentally-acquired choline to ChoP and its attachment to glycoconjugates.To date, phosphorylcholine transferase is the only known enzyme involved in ChoP protein modification. This review discusses four additional bacterial pathways for ChoP biosynthesis.Recent studies have demonstrated that ChoP is vital in mediating bacterial adhesion and colonization. Phosphorylcholine (ChoP) can be found in all life forms. Although this molecule was first thought to be uncommon in bacteria, it is now appreciated that many bacteria express ChoP on their surface. ChoP is usually attached to a glycan structure, but in some cases, it is added as a post-translational modification to proteins. Recent findings have demonstrated the role of ChoP modification and phase variation (ON/OFF switching) in bacterial pathogenesis. However, the mechanisms of ChoP synthesis are still unclear in some bacteria. Here, we review the literature and examine the recent developments in ChoP-modified proteins and glycolipids and of ChoP biosynthetic pathways. We discuss how the well-studied Lic1 pathway exclusively mediates ChoP attachment to glycans but not to proteins. Finally, we provide a review of the role of ChoP in bacterial pathobiology and the role of ChoP in modulating the immune response.