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Biochem Biophys Res Commun. 2012 Mar 23;419(4):715-8. doi: 10.1016/j.bbrc.2012.02.085. Epub 2012 Feb 22.

L-Tryptophan prevents Escherichia coli biofilm formation and triggers biofilm degradation.

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Department of Food Science and Technology, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa-shi 252-0880, Japan.


The effect of deletion of trp operon and tna operon on the Escherichia coli biofilm formation was investigated in order to elucidate the role of L-tryptophan metabolism in biofilm formation. trp operon deletion mutants ΔtrpC, ΔtrpD and ΔtrpE deficient in L-tryptophan biosynthesis showed higher biofilm formation. In addition, ΔtnaC with increased L-tryptophan degradation activity showed higher biofilm formation. On the contrary, ΔtnaA deletion mutant which lost L-tryptophan degradation activity showed low biofilm formation. From these results, it was suggested that decrease of intracellular L-tryptophan level induced biofilm formation and increase of L-tryptophan repressed biofilm formation. So the effect of the addition of L-tryptophan to the medium on the E. coli biofilm formation was investigated. L-Tryptophan addition at starting culture decreased biofilm formation and furthermore L-tryptophan addition after 16 h culture induced the degradation of preformed biofilm. From the above results, it was suggested that maintenance of high intracellular L-tryptophan concentration prevents E. coli biofilm formation and elevation of intracellular L-tryptophan concentration triggers degradation of matured biofilm.

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