Mechanistic insights in HokB-mediated persister formation and awakening

When a bacterial population is treated with high concentrations of antibiotics, there is always a small subpopulation of cells that will survive the treatment. These so-called persister cells are temporarily in an antibiotic-tolerant state, which can be based on several phenotypic changes such as a decreased antibiotic uptake, an increased repair machinery, metabolic inactivity,… Upon persister state exit, which is also called 'awakening', the cells regain growth and are again antibiotic sensitive. Persister cells pose a threat to public health care, as they are held responsible for the recalcitrance of chronic infections and they form a pool from which resistant mutants can emerge. Due to their rare and temporary nature, persister research has been proven rather challenging, and as a result, only a limited number of molecular pathways are known to induce persistence and persister awakening is still poorly understood. In this PhD, we focused on HokB-mediated persistence in E. coli to unravel molecular mechanisms underlying both entry and exit from the persister state. HokB is a membrane toxin, which forms pores in the inner membrane with an approximate radius of 1 nm. Pore formation results in energy loss via membrane depolarization and ATP leakage, eventually inducing persistence. HokB pores are stabilized by the formation of a disulfide bridge between two HokB peptides. This dimerization is effectuated by the periplasmic oxidoreductase DsbA and is essential for peptide stability and hence, pore formation. Awakening of HokB persisters depends on monomerization of the HokB dimers via the periplasmic oxidoreductase DsbC. After monomerization, the peptides are vulnerable for degradation by the periplasmic protease DegQ. Once the HokB pores are removed, the bacterial electron transport chain can repolarize the membrane, replenishing the energy pool of the persister cell and enabling regrowth.

Jaar van publicatie:2019

Toegankelijkheid:Open