N-linked protein glycosylation involves the transfer of a glycan onto an Asparagine residue (N) of a polypeptide chain. It is common in Eukaryotes and has recently been observed in Prokaryotes, most notably in Campylobacter jejuni. The C. jejuni N-linked glycosylation system is encoded on a single pgl gene locus that also functions when expressed in Escherichia coli. The key enzyme involved in N-linked protein glycosylation is encoded by the pglB gene and transfers lipid-linked glycan onto N residues of glycoproteins in the periplasm. It is clear from accumulating genome sequence data that pglB orthologues are present in all Campylobacter species and in related species such as Wolinella succinogenes, Desulfovibrio vulgaris and Desulfovibrio desulfuricans. Most Helicobacter species, including Helicobacter pylori, lack the pglB gene but three related Helicobacter species Helicobacter pullorum, Helicobacter canadensis and Helicobacter winghamensis have two distinct pglB genes. These and other orthologues of C. jejuni pgl genes are located not within a single locus but rather at five distinct loci. One of the two pglB genes, termed pglB1, is required for in vitro N-glycosylation of peptides (Jervis et al., 2010). In this thesis I present data on the role of further pgl gene orthologues and previously uncharacterized genes in H. pullorum N-glycosylation. Furthermore I have also identified a number of H. pullorum glycoproteins and provide data comparing N-glycosylation processes in C. jejuni and H. pullorum. These data expand our preliminary observations on the first Helicobacter N-linked glycosylation system, and provide important information on the similarities and differences between the well characterised C. jejuni system and these more recently identified pathways.