LAUSR

Biofilm genesis by Pseudomonas and Staphylococcus sp is associated with biofouling in natural settings. D-Tryptophan (D-Trp) inhibits bacterial biofilms and have been proposed for biofouling control applications. In this study, D-Trp significantly inhibited Pseudomonas mendocina and Staphylococcus aureus cell attachment (biofilm formation) rates on polystyrene 96-well microtiter plates in comparison with L-Tryptophan (L-Trp) and mixtures of D-/L-Tryptophan (D-/L-Trp). The inhibitory effect was greater on P. mendocina, where the rate of cell adherence was declined to 8.7 × 105 cells/h from 8.0 × 106 cells/h (control) in P. mendocina. In S. aureus it was declined to 4.2 × 107 cells/h from 9.2 × 107 cells/h (control) at 1 mM concentration. It hindered the intracellular communication and adherence in both the strains, as confirmed by SEM and real time PCR analysis. Addition of D-Trp to preformed biofilms also caused partial disassembly. Intra and interbacterial aggregation were decreased subsequently upon treatment with D-Trp. It repressed the genes involved in cell–cell communication, which could be responsible for the diminished biofilm formation of the selected strains. Hence D-Tryptophan has proved to be an effective strategy to control biofilm and may support in the development of surface coating technologies.