Effects of Different Amino Acids on Biofilm Growth, Swimming Motility and Twitching Motility in Escherichia Coli BL21

Biofilms are surface-attached, matrix-enclosed microbial communities that can cause various diseases like formation of dental plague, urinary tract infection and cystic fibrosis. The purpose of this study was to examine the effects of amino acids (arginine, valine, leucine, glycine, lysine, phenylalanine, threonine and proline) on biofilm formation swimming motility and twitching motility in Escherichia coli BL21. M63 minimal salt media (supplemented with different types and concentrations of amino acids) were used for induction of biofilm formation and the resulting biofilm growth was quantified spectrophotometrically at optical density of 550 nm after 24 hours of inoculation. For swimming and twitching motility assays, amino acid-supplemented tryptone and Luria-Bertani agar plates were used and the diameter of halo formed in the agar was measured after the same duration. The eight amino acids tested showed varied effects on biofilm formation, swimming motility and twitching motility in E. coli BL21. Leucine, glycine, threonine and proline promoted both twitching and swimming motility up to about 100%. Arginine and valine increased swimming motility up to 50% but had no effect on twitching motility. Lysine and phenylalanine completely inhibited both swimming and twitching motility in the bacteria. With regard to biofilm formation, both leucine and valine promoted it up to a maximum of 25%. However, glycine, lysine, phenylalanine, and threonine inhibited biofilm formation; proline and arginine showed inhibitory effects only at higher concentrations (0.4%). These results suggest that amino acids may play a role in inhibiting or promoting biofilm formation. The potential use of amino acid-based dietary supplements to control biofilm formation and ultimately to treat its associated diseases warrants further investigation.