The EPS matrix can limit oxygen availability and reduce bacterial metabolic activity, which is an important factor protecting biofilm bacteria from antibiotics. The EPS matrix also introduces a diffusion limitation for drugs,, thus most of the antibiotics cannot penetrate to the full depth of the biofilm, resulting in reduced rates of killing of bacterial cells present within the biofilm. Bacterial cell surface appendages play a major role in biofilm formation. Fimbriae are hair-like surface appendages that are directly involved in the attachment of bacteria to various surfaces. Flagella are helical filaments that protrude from the cell body and are largely responsible for bacterial motility. A mutation in, or down-regulation of major UPEC flagellar genes could impede or completely block bacterial motility,, leading to an increase in biofilms, but also decreasing the ability of bacteria to disseminate and cause infection. In the present study, we investigated the hypothesis that exposure to the alkaloids PIP and RES could WZ8040 affect the colonization behaviour of the uropathogenic bacterium E. coli CFT073. We examined bacterial motility, ability to form biofilms and expression of genes relevant to bacterial motility and surface attachment in the presence of these alkaloids. Finally, we examined the effect of PIP and RES on the ability of the antibiotics ciprofloxacin and azithromycin to penetrate into and disperse pre-established E. coli CFT073 biofilms. We investigated two natural compounds, PIP and RES, for their ability to affect the motility and biofilm formation of uropathogenic E. coli CFT073. The alkaloids exhibited minimal effect on bacterial growth; however, biofilm formation significantly increased for bacterial cells incubated with both PIP and RES. These results are in agreement with earlier reports wherein cranberry and pomegranate materials, also containing alkaloids, were observed to block bacterial motility, and increase biofilm formation. Although at first instance, increase in biofilm formation seems a disadvantage in a therapeutic context, it should be noted that this effect is accompanied by a significant decrease in motility which has been reported to decrease the spread of infection. E. coli possess peritrichous flagella which contribute to bacterial swimming in liquid media and, to some extent, to their movement along surfaces, thereby promoting the spread of infection. We report a decrease in bacterial motility which can potentially hamper the dissemination of infection. It is noteworthy that PIP decreased both swimming and swarming motilities. Unlike swimming motility which is a single cell act, swarming motility is a social behaviour and bacterial cells have to communicate to be able to swarm. This communication, known as quorum sensing, is a major virulence factor and decreased swarming has been correlated with decreased quorum sensing, and thus, decreased virulence. Thus, it would be interesting to evaluate in future studies whether PIP could act as an anti-quorum sensing agent.