We hypothesised that colicin proteins labelled with mannose sugars could form the basis of novel non-bactericidal agents against adhesive bacteria. Colicins are small proteins produced by some E. coli strains which are toxic to others, and bind to their target receptors with high (i.e. nanomolar) affinity. They are promising agents for use in therapeutic contexts, as their narrow targeting range could potentially facilitate single-strain targeting while the lack of their target receptor on mammalian cells means off-target interactions are unlikely. Notably, while native colicins are used as offensive weapons against competing E. coli strains, Penfold et al demonstrated that the installation of a 'top lock' in the R-domain of colicin E9 inhibits toxicity while not adversely affecting the binding of colicin E9 to its target receptor (the BtuB outer membrane protein receptor), thereby allowing colicin E9 to serve as a non-bactericidal agent for labelling E. coli. Herein, we present the design and synthesis of colicin conjugates presenting functional motifs, such as i) biotin, ii) fluorescein and iii) α-D-mannopyranosides. We demonstrate that the conjugation of functional motifs to colicin E9 can be achieved by an organocatalyst-mediated protein aldol ligation (OPAL) (Figure ), and that appending functional motifs to colicin E9 does not prevent the binding of the protein to its target BtuB receptor (Figure ). Furthermore, we demonstrate the premise of using α-D-mannose presenting colicin E9 neoglycoproteins as hetero bi-selective binding agents that can induce aggregation in samples of E. coli K12 substr. BW25113 via the simultaneous binding of FimH and BtuB motifs. We propose that the initial highaffinity binding of colicin units to constitutively expressed (~500 per cell) BtuB receptors (Figure ) results in the labelling of E. coli surfaces with multiple α-D-mannose motifs, which are thereafter capable of multivalent binding to FimH adhesins on neighbouring bacterial surfaces.