Far-reaching cellular consequences of tat deletion in Escherichia coli revealed by comprehensive proteome analyses

In Escherichia coli, the Twin-arginine translocation (Tat) pathway secretes a set of folded proteins with important physiological functions to the periplasm and outer membrane. The loss of Tat secretion impairs outer membrane integrity and leads to decreased cell growth. Only recently, the Tat pathway has gained more attention due to its essential role in bacterial virulence and applications in the production of fully folded heterologous proteins. In this study, we investigated the influence of the deletion of all active Tat pathway components on the E. coli cells. The comprehensive proteomic analysis revealed activation of several stress responses and experimentally confirmed the dependence of certain proteins on the Tat system for export. We observed that a tat deletion triggers protein aggregation, membrane vesiculation, synthesis of colanic acid and biofilm formation. Furthermore, the mislocalization of Tat-dependent proteins disturbs iron and molybdenum homeostasis and impairs the cell envelope integrity. The results show that the functional Tat pathway is important for the physiological stability and that its dysfunction leads to a series of severe changes in E. coli cells.