The interactions of natural compounds with Escherichia coli motility, attachment, communication systems, and mature biofilm.

Bacterial biofilms play a significant role in increasing antibiotic resistance and the pathogenesis of Escherichia coli; their control is a major challenge in treating bacterial infections. In recent years, natural compounds have emerged as effective alternatives for inhibiting the formation and destruction of bacterial biofilms. Natural compounds such as curcumin, cinnamaldehyde, eugenol, carvacrol, quercetin, resveratrol, thymol, citral, and catechin are noteworthy in hindering and destroying E. coli biofilms. They inhibit bacterial motility (swarming and swimming), reducing attachment to surfaces, and downregulate genes related to attachment and motility (fimH, csgABC, sfaAS, papG, fliAC, flhCD, and motAB). Natural compounds can also disrupt the bacterial communication system and cause changes in the expression of luxS, sdiA, tnaA, qseBC, bssS, and lsrR genes. Studies have also shown that natural compounds can destroy mature biofilms' structure and decrease biofilm exopolysaccharides' production. This impact makes the bacteria more sensitive to the antimicrobial agents. However, one of the biggest challenges in using natural compounds is their low stability and restricted bioavailability in biological environments. For this reason, utilizing nanoparticles and novel drug delivery systems can improve these compounds' stability, penetrability, and efficacy. This article reviews the antibiofilm potential of natural compounds, their mechanisms of activity in hindering and destroying E. coli biofilms, and the role of nanotechnology in improving the performance of these compounds.