Phytopathogenic bacteria Pantoea stewartii subsp. stewartii (DC 283) has been demonstrated to aggregate in the gut and causes the death of the pea aphid (Acyrthosiphon pisum) by a flocculating behaviour that prevents honey dew secretion. This behaviour has been attributed to the (you cannot pass-1) ucp1 gene that potentially has an outer membrane function. Here we further explore the role of the ucp1 gene transformed into E. coli (pET21B) by atomic force microscopy and the effects of its expression on the ultrastructure and morphology of the E. coli (pET21B) cell surface. Induction of Ucp1 at various levels was correlated with aggregation of E. coli cells up to 95%. EPS material was produced in larger amounts around bacterial cells with higher induction levels of Ucp1. Interestingly, the surface subunits increased almost 10 nm in size when Ucp1 was induced, and stayed constant over different levels of induction. These results show that Ucp1 indeed has either a direct or indirect role on the ultrastructure of the E. coli cell wall surface, leading to aggregation behaviour.