Department of Food Science and Technology, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa-shi 252-0880, Japan.
Biochem Biophys Res Commun. 2012 Mar 23;419(4):715-8. doi: 10.1016/j.bbrc.2012.02.085. Epub 2012 Feb 22.
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.
为了阐明色氨酸代谢在生物膜形成中的作用，研究了 trp 操纵子和 tna 操纵子缺失对大肠杆菌生物膜形成的影响。色氨酸生物合成缺陷型 trp 操纵子缺失突变体ΔtrpC、ΔtrpD 和ΔtrpE 表现出更高的生物膜形成能力。此外，L-色氨酸降解活性增加的ΔtnaC 表现出更高的生物膜形成能力。相反，丧失 L-色氨酸降解活性的ΔtnaA 缺失突变体表现出低的生物膜形成能力。这些结果表明，细胞内 L-色氨酸水平的降低诱导生物膜形成，而 L-色氨酸的增加抑制生物膜形成。因此，研究了向培养基中添加 L-色氨酸对大肠杆菌生物膜形成的影响。在起始培养时添加 L-色氨酸会降低生物膜形成，而且在 16 小时培养后添加 L-色氨酸会诱导已形成的生物膜降解。从这些结果可以看出，维持高细胞内 L-色氨酸浓度可以防止大肠杆菌生物膜形成，而升高细胞内 L-色氨酸浓度会触发成熟生物膜的降解。
