Decoupling filamentous phage uptake and energy of the TolQRA motor in Escherichia coli .
Résumé
Filamentous phages are non-lytic viruses that specifically infect bacteria, establishing a persistent association with their host. The phage particle has no machinery for generating energy and parasitizes its host existing structures in order to cross the bacterial envelope and deliver its genetic material. The import of filamentous phages across the bacterial periplasmic space requires some of the components of a macro-complex of the envelope known as the Tol system. This complex uses the energy provided by the proton-motive force of the inner membrane to perform essential and highly energy-consuming functions of the cell, such as envelope integrity maintenance and cell division. It has been suggested that phages take advantage of pmf-driven conformational changes in the Tol system to transit across the periplasm. However, this hypothesis has not been formally tested. In order to decouple the role of the Tol system in cell physiology and during phage parasitism, we used mutations on conserved essential residues known for inactivating pmf-dependent functions of the Tol system. We identified impaired Tol complexes that remain fully efficient for filamentous phage uptake. We further demonstrate that the TolQ-TolR homologous motor, ExbB-ExbD, normally operating with the TonB protein, is able to promote phage infection along with full length TolA.
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