Following successful demonstration of colicin E9 OPAL labelling as a reliable method for appending biologically relevant molecules to the surface of E. coli. We hypothesized that a mannose-presenting colicin E9 conjugate could be used to label the surface of E. coli with multiple glycans, effectively turning each bacterium into a mannose presenting 'glyco-dendrimer'. Surface exposed mannose units may then bind FimH units on nearby E. coli cells, resulting in cell-tocell adhesion and potentially aggregation. To test this hypothesis a mannose-bearing OPAL probe first had to be synthesised. Many different mannose scaffolds have previously been investigated for use against UPEC, including biphenyl mannosides, (neo)thiazolylaminomannosides, septanose, and squarate mannosides. An αmannose presenting squarate mannoside scaffold was identified as suitable for appending to an OPAL probe as i) mannose azide 4 could be synthesized relatively simply in four steps (figure ), ii) squarate mannosides have been shown in literature to have high affinity for FimH, with analogues achieving IC50 values in the micromolar range, and iii) the squarate ester scaffold allows for easy installation of bioconjugation handles through the substitution of the terminal squarate methoxy group with an appropriate amine.