Important human pathogens such as Escherichia coli, Salmonella and Legionella, are all Gram-negative bacteria, the defining feature of which is an outer membrane that encapsulates the cell. Many outer membrane proteins form large protein complexes essential for outer membrane biogenesis and cell survival. In pathogenic strains, outer membrane protein machinery also play a central role in initiating productive infections. The majority of outer membrane proteins embedded in the lipid bilayer have a typical β-barrel fold. They are reliant on an outer membrane protein complex called the β-barrel assembly machinery (BAM) that ensures protein folding and insertion into the membrane occurs correctly and efficiently. In E.coli, BAM is composed of five subunits: BamA, BamB, BamC, BamD and BamE. BamA is itself a b-barrel protein containing a periplasmic domain thought to scaffold the remaining components. The four accessory lipoproteins are anchored to the outer membrane and like most known lipoproteins, assumed to face into the periplasm. Our recent analysis of the BAM component BamC however disputes this current model and suggests the BAM complex spans the outer membrane displaying functional modules not only in the periplasmic space but also on the cell surface1 . Work now continues to characterise the membrane-spanning region of BamC to elucidate the mechanism by which it is transported to, and assembled on the cell surface.