Evolution and Conservation of Intracellular Survival in Eukaryotic Host Cells.

The classical bordetellae possess several partially characterized virulence mechanisms that are studied in the context of a complete extracellular life cycle in their mammalian hosts. Yet, classical bordetellae have repeatedly been reported within dendritic cells (DCs) and alveolar macrophages in clinical samples, and experiments convincingly demonstrate that the bacteria can survive intracellularly within mammalian phagocytic cells, an ability that appears to have descended from ancestral progenitor species that lived in the environment and acquired the mechanisms to resist unicellular phagocytic predators. Many pathogens, including , , , and , are known to parasitize and multiply inside eukaryotic host cells. This strategy provides protection, nutrients, and the ability to disseminate systemically. While some work has been dedicated at characterizing intracellular survival of , there is limited understanding of how this strategy has evolved within the genus and the contributions of this ability to bacterial pathogenicity, evasion of host immunity as well as within and between-host dissemination. Here, we explore the mechanisms that control the metabolic changes accompanying intracellular survival and how these have been acquired and conserved throughout the evolutionary history of the genus and discuss the possible implications of this strategy in the persistence and reemergence of in recent years.